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==Description==
==Description==
=== Size ===
=== Size ===
[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and 317&nbsp;kg, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" />
[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and {{Convert|317|kg|lb|abbr=on}}, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" />


Though over 100 giant short-faced bear localities in [[North America]] are known, only one site produced a [[baculum]] (penis bone) that could belong to ''Arctodus simus''. The lack of recovered ''Arctodus'' [[Baculum|bacula]] likely reflects both [[taphonomy]] and behaviour. The majority of skeletal remains representing large individuals are from open sites where usually only a few elements were recovered. In contrast, horizontal (walk-in) cave passages produced numerous examples of small, yet relatively complete individuals where [[Baculum|bacula]] would likely be found if they had been present. Both the small size of recovered skeletal elements and the lack of [[Baculum|bacula]] from cave deposits suggest that female individuals of ''A. simus'' were using caves, in line with [[Bear|ursid]] maternal denning.<ref name=":2">{{Cite journal|last1=CHUBERT|first1=BLAINE|last2=KAUFMANN|first2=JAMES|date=2003-08-01|title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species|url=https://www.researchgate.net/publication/252748398|journal=Journal of Cave and Karst Studies|volume=65}}</ref><ref name=":3">{{Cite journal|last1=Fowler|first1=Nicholas L.|last2=Spady|first2=Thomas J.|last3=Wang|first3=Guiming|last4=Leopold|first4=Bruce D.|last5=Belant|first5=Jerrold L.|date=October 2021|title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51|issue=4|pages=465–481|doi=10.1111/mam.12246|s2cid=233847639 }}</ref> Therefore, in conjunction with ursid sexual dimorphism (e.g. in [[spectacled bear]]s, males are 30%-40% larger than females), the largest individuals are often considered male, particularly older males, with the smaller individuals being females.<ref name=":02"/><ref name=":12">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |doi=10.1016/j.quaint.2009.11.010 |bibcode=2010QuInt.217..188S }}</ref><ref name=":46">{{Cite journal |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |journal=PaleoBios |volume=15 |issue=2 |pages=27–36 |date=May 24, 1993 |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf}}</ref>
Though over 100 giant short-faced bear localities in [[North America]] are known, only one site produced a [[baculum]] (penis bone) that could belong to ''Arctodus simus''. The lack of recovered ''Arctodus'' [[Baculum|bacula]] likely reflects both [[taphonomy]] and behaviour. The majority of skeletal remains representing large individuals are from open sites where usually only a few elements were recovered. In contrast, horizontal (walk-in) cave passages produced numerous examples of small, yet relatively complete individuals where [[Baculum|bacula]] would likely be found if they had been present. Both the small size of recovered skeletal elements and the lack of [[Baculum|bacula]] from cave deposits suggest that female individuals of ''A. simus'' were using caves, in line with [[Bear|ursid]] maternal denning.<ref name=":2">{{Cite journal|last1=CHUBERT|first1=BLAINE|last2=KAUFMANN|first2=JAMES|date=2003-08-01|title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species|url=https://www.researchgate.net/publication/252748398|journal=Journal of Cave and Karst Studies|volume=65}}</ref><ref name=":3">{{Cite journal|last1=Fowler|first1=Nicholas L.|last2=Spady|first2=Thomas J.|last3=Wang|first3=Guiming|last4=Leopold|first4=Bruce D.|last5=Belant|first5=Jerrold L.|date=October 2021|title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51|issue=4|pages=465–481|doi=10.1111/mam.12246|s2cid=233847639 }}</ref> Therefore, in conjunction with ursid sexual dimorphism (e.g. in [[spectacled bear]]s, males are 30%-40% larger than females), the largest individuals are often considered male, particularly older males, with the smaller individuals being females.<ref name=":02"/><ref name=":12">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |doi=10.1016/j.quaint.2009.11.010 |bibcode=2010QuInt.217..188S }}</ref><ref name=":46">{{Cite journal |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |journal=PaleoBios |volume=15 |issue=2 |pages=27–36 |date=May 24, 1993 |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf}}</ref>


Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~555&nbsp;kg.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1994 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~372&nbsp;kg, smaller than recovered [[brown bear]] remains (~455&nbsp;kg, although these remains may postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~770&nbsp;kg from six specimens.<ref name=":7" />
Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~{{Convert|555|kg|lb}}.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1998 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~{{Convert|372|kg|lb}}, smaller than recovered [[brown bear]] remains (~{{Convert|455|kg|lb}}, although these remains postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~{{Convert|770|kg|lb}} from six specimens.<ref name=":7" />


Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between 1,200&nbsp;kg and 412&nbsp;kg,<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between 957&nbsp;kg (~1,000&nbsp;kg) and 317&nbsp;kg.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref>
Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between {{Convert|1200|kg|lb}} and {{Convert|412|kg|lb}},<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between {{Convert|957|kg|lb}} and {{Convert|317|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref>


=== Data ===
=== Data ===
Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]].<ref name=":6" /><ref name=":62"/> Also included are the mean figures from [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref>
Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]],<ref name=":6" /><ref name=":62"/> and some associated weight estimates.<ref name="Figueiridio_et_al_20102" /> Also included is the mean from 9 specimens in [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref>
{| class="wikitable sortable"
{| class="wikitable sortable"
|+
|+
!Ratio of TL to TW (M) x 100
!Ratio of TL to TW (M) x 100
!Standard Deviation
!Standard Deviation
!Estimated weight (kg)
!Number
|-
|-
|P.89.13.91, [[Edmonton]]
|P.89.13.91, [[Edmonton]]
|9.0
|9.0
|~
|~
|1
|~
|-
|-
|UVP 015/1, Utah
|UVP 015/1, Utah
|8.9
|8.9
|~
|~
|1
|957
|-
|-
|UC 3721, [[Shasta Lake|Potter Creek Cave]]
|UC 3721, [[Shasta Lake|Potter Creek Cave]]
|8.3
|8.3
|~
|~
|1
|~
|-
|-
|F:AM 25531, [[Hay Springs, Nebraska|Hay Springs]]
|F:AM 25531, [[Hay Springs, Nebraska|Hay Springs]]
|9.5
|9.5
|~
|~
|1
|863
|-
|-
|UM 25611, [[Meade, Kansas|Jinglebob]]
|UM 25611, [[Meade, Kansas|Jinglebob]]
|8.5
|8.5
|~
|~
|1
|388
|-
|-
|UC 44687, [[Irvington, California|Irvington]]
|UC 44687, [[Irvington, California|Irvington]]
|9.1
|9.1
|~
|~
|1
|~
|-
|-
|LACMNH-Z75, [[La Brea Tar Pits|Rancho La Brea]]
|LACMNH-Z75, [[La Brea Tar Pits|Rancho La Brea]]
|~
|~
|~
|~
|1
|317
|-
|-
|U.S.A. sites, x̄ values (Kurtén, 1967)
|U.S.A. sites, x̄ values (Kurtén, 1967)
|8.1-9.5 (x̄= 8.7)
|8.1-9.5 (x̄= 8.7)
|0.45
|0.45
|9
|~
|}
|}


==== Skull ====
==== Skull ====
[[File:Arctodus simus skull Cleveland.jpg|thumb|''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], [[Ohio]]]]
[[File:Arctodus simus skull Cleveland.jpg|thumb|''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], [[Ohio]]]]
Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] are likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" />
Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] were likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" />


The skull also has a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance; this broad [[snout]] possibly housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas (although this is characteristic shared with the omni-herbivorous spectacled bear).<ref name=":7" /><ref name=":132">{{Cite journal |last1=Emslie |first1=Steven D. |last2=Czaplewski |first2=Nicholas J. |date=1985-11-15 |title=A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology |url=https://www.biodiversitylibrary.org/partpdf/226835 |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793}}</ref><ref name=":402">{{Cite journal |last=Matheus |first=Paul E. |date=1995-11-01 |title=Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0033589485710903 |journal=Quaternary Research |language=en |volume=44 |issue=3 |pages=447–453 |doi=10.1006/qres.1995.1090 |bibcode=1995QuRes..44..447M |s2cid=83542760 |issn=0033-5894}}</ref><ref>{{Cite journal |last1=Goswami |first1=Anjali |last2=Milne |first2=Nick |last3=Wroe |first3=Stephen |date=2011-06-22 |title=Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1713 |pages=1831–1839 |doi=10.1098/rspb.2010.2031 |issn=0962-8452 |pmc=3097826 |pmid=21106595}}</ref> The [[Orbit (anatomy)|orbits]] of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat [[Lateral (anatomy)|laterally orientated]] (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the [[brown bear]], suggesting that [[Stereopsis|stereoscopic vision]] was not a priority.<ref name=":110"/><ref name=":302"/><ref name=":292">{{Cite book |last=Baryshnikov |first=Gennady |url=https://www.researchgate.net/publication/336916777 |title=The Hot Springs Mammoth Site: A Decade of Field and Laboratory Research in Paleontology, Geology and Paleoecology |publisher=The Mammoth Site of Hot Springs, South Dakota Inc. |year=1994 |editor-last=Agenbroad |editor-first=Larry D. |pages=Chapter 16 |editor-last2=Mead |editor-first2=Jim I.}}</ref>
The skull also has a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance; this broad [[snout]] possibly housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas (although this is characteristic shared with the omni-herbivorous spectacled bear).<ref name=":7" /><ref name=":132">{{Cite journal |last1=Emslie |first1=Steven D. |last2=Czaplewski |first2=Nicholas J. |date=1985-11-15 |title=A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology |url=https://www.biodiversitylibrary.org/partpdf/226835 |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793}}</ref><ref name=":402">{{Cite journal |last=Matheus |first=Paul E. |date=1995-11-01 |title=Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0033589485710903 |journal=Quaternary Research |language=en |volume=44 |issue=3 |pages=447–453 |doi=10.1006/qres.1995.1090 |bibcode=1995QuRes..44..447M |s2cid=83542760 |issn=0033-5894}}</ref><ref>{{Cite journal |last1=Goswami |first1=Anjali |last2=Milne |first2=Nick |last3=Wroe |first3=Stephen |date=2011-06-22 |title=Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1713 |pages=1831–1839 |doi=10.1098/rspb.2010.2031 |issn=0962-8452 |pmc=3097826 |pmid=21106595}}</ref> The [[Orbit (anatomy)|orbits]] of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat [[Lateral (anatomy)|laterally orientated]] (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the [[brown bear]], suggesting that [[Stereopsis|stereoscopic vision]] was not a priority.<ref name=":110"/><ref name=":302"/><ref name=":292">{{Cite book |last=Baryshnikov |first=Gennady |url=https://www.researchgate.net/publication/336916777 |title=The Hot Springs Mammoth Site: A Decade of Field and Laboratory Research in Paleontology, Geology and Paleoecology |publisher=The Mammoth Site of Hot Springs, South Dakota Inc. |year=1994 |editor-last=Agenbroad |editor-first=Larry D. |pages=Chapter 16 |editor-last2=Mead |editor-first2=Jim I.}}</ref>
Although the shape of the [[Elbow|elbow joint]] suggests ''Arctodus'', ''[[Arctotherium|Arctotherium bonariense]]'', and ''[[Arctotherium|Arctotherium wingei]]'' had the possibility of retaining [[Arboreal locomotion|semi-arboreal]] adaptations, the size of the elbow joint condemns ''Arctodus'' to terrestrial life. As the [[Medial epicondyle of the humerus|medial epicondyle]] is particularly expanded in these species, it is likely that ''Arctodus'' and ''Arctotherium'' (just like the [[giant panda]]) retained this characteristic to attain a higher degree of forelimb dexterity. Whether this dexterity facilitated [[Scavenger|scavenging]] or [[Herbivore|herbivory]], this high degree of proximal dexterity was probably advantageous for these species, and retained in tremarctine bears despite their general tendency towards terrestriality.<ref name=":28">{{Cite journal|last1=Mitchell|first1=Kieren J.|last2=Bray|first2=Sarah C.|last3=Bover|first3=Pere|last4=Soibelzon|first4=Leopoldo|last5=Schubert|first5=Blaine W.|last6=Prevosti|first6=Francisco|last7=Prieto|first7=Alfredo|last8=Martin|first8=Fabiana|last9=Austin|first9=Jeremy J.|last10=Cooper|first10=Alan|date=2016-04-30|title=Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America|journal=Biology Letters|volume=12|issue=4|pages=20160062|doi=10.1098/rsbl.2016.0062|pmc=4881349|pmid=27095265}}</ref><ref name=":132"/><ref name="Meloro 133–146">{{Cite journal|last1=Meloro|first1=Carlo|last2=de Oliveira|first2=Alessandro Marques|date=2019-03-01|title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |journal=Journal of Mammalian Evolution |volume=26|issue=1|pages=133–146|doi=10.1007/s10914-017-9413-x|s2cid=25839635 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf}}</ref>
Although the shape of the [[Elbow|elbow joint]] suggests ''Arctodus'', ''[[Arctotherium|Arctotherium bonariense]]'', and ''[[Arctotherium|Arctotherium wingei]]'' had the possibility of retaining [[Arboreal locomotion|semi-arboreal]] adaptations, the size of the elbow joint condemns ''Arctodus'' to terrestrial life. As the [[Medial epicondyle of the humerus|medial epicondyle]] is particularly expanded in these species, it is likely that ''Arctodus'' and ''Arctotherium'' (just like the [[giant panda]]) retained this characteristic to attain a higher degree of forelimb dexterity. Whether this dexterity facilitated [[Scavenger|scavenging]] or [[Herbivore|herbivory]], this high degree of proximal dexterity was probably advantageous for these species, and retained in tremarctine bears despite their general tendency towards terrestriality.<ref name=":28">{{Cite journal|last1=Mitchell|first1=Kieren J.|last2=Bray|first2=Sarah C.|last3=Bover|first3=Pere|last4=Soibelzon|first4=Leopoldo|last5=Schubert|first5=Blaine W.|last6=Prevosti|first6=Francisco|last7=Prieto|first7=Alfredo|last8=Martin|first8=Fabiana|last9=Austin|first9=Jeremy J.|last10=Cooper|first10=Alan|date=2016-04-30|title=Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America|journal=Biology Letters|volume=12|issue=4|pages=20160062|doi=10.1098/rsbl.2016.0062|pmc=4881349|pmid=27095265}}</ref><ref name=":132"/><ref name="Meloro 133–146">{{Cite journal|last1=Meloro|first1=Carlo|last2=de Oliveira|first2=Alessandro Marques|date=2019-03-01|title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |journal=Journal of Mammalian Evolution |volume=26|issue=1|pages=133–146|doi=10.1007/s10914-017-9413-x|s2cid=25839635 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf}}</ref>


A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" />
A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" /> ''Arctodus'' likely had a top speed of {{Convert|40-45|km/h|mph}}, and based on hyaenid proportions, would shift from singlefoot locomotion to a pace at {{Convert|8.5|km/h|mph|abbr=on}}, and would begin to gallop at {{Convert|18.5|km/h|mph|abbr=on}}, a fairly high speed. Based on other mammals, the optimal pace speed of ''Arctodus'' would have been {{Convert|13.7|km/h|mph|abbr=on}}, which would have also been rather fast for moderate speed travel. For comparison, hyenas cross country ~{{Convert|10|km/h|mph|abbr=on}}.<ref name=":212" />


The [[paw]]s ([[metapodial]]s and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''' paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the first digit ([[Toe|hallux]]) of ''Arctodus'' was positioned more closely and parallel to the other four digits (i.e. with straight toes, ''Arctodus'' had less lateral splaying).<ref name=":272">{{Cite thesis |title=Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia |url=https://scholarworks.alaska.edu/handle/11122/9491 |date=1997 |degree=PhD |language=en |first=Paul Edward |last=Matheus}}</ref> This theory is potentially contradicted by trackways tentatively attributed to ''Arctodus'' from near [[Lakeview, Oregon|Lakeview]] in [[Oregon]]. The trackways, which fit the dimensions of ''Arctodus simus''<nowiki/>' paws, exhibit extreme toe splaying, with three centrally aligned, evenly spaced toes at the front, and two almost perpendicular toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had an oval-shaped, undivided pad on its sole (with no toe pad impressions), with front paws that were slightly larger than its back paws, possessed long claws, and had its hind foot overstep the forefoot when walking, like modern bears.<ref>{{Cite web |last1=Packard |first1=E.L. |last2=Allison |first2=I.S. |last3=Cressman |first3=L.S. |title=Mammalian Tracks in the Late Pliocene or Early Pleistocene Beds of Lake County Oregon |url=https://www.oregongeology.org/milo/archive/MiningDistricts/LakeCounty/UnclassifiedDistrict/LakeCountyFossilLocalities/LakeCountyFossilLocalitiesReports.pdf |access-date=June 11, 2017 |website=Oregon Geology}}</ref> For comparison, the [[Manus (anatomy)|manus]] of the spectacled bear has five digits arrayed in a shallow arc, and claws which are quite long, and which also extend far in front of their respective digits.<ref>{{Cite journal |last=Weems |first=Robert E. |date=2018 |title=An Early Pleistocene (Early Irvingtonian) Footprint Fauna from the Bacons Castle Formation, Westmoreland Formation, Virginia |url=https://www.researchgate.net/publication/348579743 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=79 |pages=731–748 |via=ResearchGate}}</ref> Some claw marks attributed to ''Arctodus simus'' at [[Riverbluff Cave]] (as they were four meters above the floor of the cave) were nearly 20&nbsp;cm in width.<ref name=":1">{{Cite journal |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |title=Cenozoic Vertebrate Tracks and Traces |last2=Spielmann |first2=Justin A. |last3=Lockley |first3=Martin G. |date=2007 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=42 |language=en}}</ref>
The [[paw]]s ([[metapodial]]s and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''' paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the first digit ([[Toe|hallux]]) of ''Arctodus'' was positioned more closely and parallel to the other four digits (i.e. with straight toes, ''Arctodus'' had less lateral splaying).<ref name=":272">{{Cite thesis |title=Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia |url=https://scholarworks.alaska.edu/handle/11122/9491 |date=1997 |degree=PhD |language=en |first=Paul Edward |last=Matheus}}</ref> This theory is potentially contradicted by trackways tentatively attributed to ''Arctodus'' from near [[Lakeview, Oregon|Lakeview]] in [[Oregon]]. The trackways, which fit the dimensions of ''Arctodus simus''<nowiki/>' paws, exhibit extreme toe splaying, with three centrally aligned, evenly spaced toes at the front, and two almost perpendicular toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had an oval-shaped, undivided pad on its sole (with no toe pad impressions), with front paws that were slightly larger than its back paws, possessed long claws, and had its hind foot overstep the forefoot when walking, like modern bears.<ref>{{Cite web |last1=Packard |first1=E.L. |last2=Allison |first2=I.S. |last3=Cressman |first3=L.S. |title=Mammalian Tracks in the Late Pliocene or Early Pleistocene Beds of Lake County Oregon |url=https://www.oregongeology.org/milo/archive/MiningDistricts/LakeCounty/UnclassifiedDistrict/LakeCountyFossilLocalities/LakeCountyFossilLocalitiesReports.pdf |access-date=June 11, 2017 |website=Oregon Geology}}</ref> For comparison, the [[Manus (anatomy)|manus]] of the spectacled bear has five digits arrayed in a shallow arc, and claws which are quite long, and which also extend far in front of their respective digits.<ref>{{Cite journal |last=Weems |first=Robert E. |date=2018 |title=An Early Pleistocene (Early Irvingtonian) Footprint Fauna from the Bacons Castle Formation, Westmoreland Formation, Virginia |url=https://www.researchgate.net/publication/348579743 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=79 |pages=731–748 |via=ResearchGate}}</ref> Some claw marks attributed to ''Arctodus simus'' at [[Riverbluff Cave]] (as they were four meters above the floor of the cave) were nearly 20&nbsp;cm in width.<ref name=":1">{{Cite journal |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |title=Cenozoic Vertebrate Tracks and Traces |last2=Spielmann |first2=Justin A. |last3=Lockley |first3=Martin G. |date=2007 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=42 |language=en}}</ref>
One past proposal, suggested by [[Björn Kurtén]], envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed the [[megafauna]] of the Pleistocene with its great physical strength.<ref name=":162"/> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":212">{{Cite book |last=E. |first=Matheus, Paul |title=Locomotor adaptations and ecomorphology of short-faced bears (Arctodus simus) in eastern Beringia |date=2003 |publisher=Yukon Palaeontologist, Gov't. of Yukon |oclc=243520303}}</ref><ref name=":222">{{Cite book |last=Randally |first=Lynch, Eric |title=Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics |date=2012-08-06 |publisher=East Tennessee State University |oclc=818344518}}</ref> significantly more [[Gracility|gracile]] so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":202">{{Cite journal |last1=SOIBELZON |first1=LEOPOLDO H. |last2=SCHUBERT |first2=BLAINE W. |date=2011 |title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears |journal=Journal of Paleontology |volume=85 |issue=1 |pages=69–75 |doi=10.1666/10-037.1 |jstor=23019499 |s2cid=129585554}}</ref>
One past proposal, suggested by [[Björn Kurtén]], envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed the [[megafauna]] of the Pleistocene with its great physical strength.<ref name=":162"/> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":212">{{Cite book |last=E. |first=Matheus, Paul |title=Locomotor adaptations and ecomorphology of short-faced bears (Arctodus simus) in eastern Beringia |date=2003 |publisher=Yukon Palaeontologist, Gov't. of Yukon |oclc=243520303}}</ref><ref name=":222">{{Cite book |last=Randally |first=Lynch, Eric |title=Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics |date=2012-08-06 |publisher=East Tennessee State University |oclc=818344518}}</ref> significantly more [[Gracility|gracile]] so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":202">{{Cite journal |last1=SOIBELZON |first1=LEOPOLDO H. |last2=SCHUBERT |first2=BLAINE W. |date=2011 |title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears |journal=Journal of Paleontology |volume=85 |issue=1 |pages=69–75 |doi=10.1666/10-037.1 |jstor=23019499 |s2cid=129585554}}</ref>


Because its long legs may have enabled ''Arctodus'' to run at speeds of {{Convert|50|-|70|km/h|abbr=on|sigfig=1|mph}}, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref name=":212" /><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/>
Due to their long legs, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. Correspondingly, although a 700''&nbsp;''kg ''Arctodus'' may have been able to reach a maximum speed of {{Convert|51|km/h|mph}}, all modern bears have maximum speeds significantly lower than mass based calculations for speed- such speeds would have likely exceeded skeletal strength with their bulk. As a result, paleontologist Paul Matheus suggests that ''Arctodus''<nowiki/>' top speed was {{Convert|40-45|km/h|mph|abbr=on}}. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/>


Additionally, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/>
Moreover, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/>


However, analysis of the forelimb of ''Arctodus'' suggests the bear could have been in the early stages of [[cursorial]] evolution- ''A. simus'' was somewhat more prone to [[Cursorial|cursorial tendencies]], being capable of more efficient locomotion, ''A. simus'' was interpreted as capable of high-speed (relative to extant bears), straight-line locomotion, and was likely more adept at pursuing large prey than the extant [[Polar bear|polar]] and [[brown bear]]s.<ref name=":222" /> However, that the limbs are elongated in the proximal rather than distal limb segments, had a plantigrade gait, and a stride which had little to no unsupported intervals, put doubt to this theory.<ref name=":132"/> Moreover, the pronation of the forearm and the flexion of the wrist and digits, and more lightly muscled forelimbs, all of which are crucial to grasping a large prey animal with the forepaws, were probably less powerful in ''Arctodus'' than in either the [[brown bear]] or in ''[[Panthera]].''<ref name=":110" />
However, analysis of the forelimb of ''Arctodus'' suggests the bear could have been in the early stages of [[cursorial]] evolution- ''A. simus'' was somewhat more prone to [[Cursorial|cursorial tendencies]], being capable of more efficient locomotion, ''A. simus'' was interpreted as capable of high-speed (relative to extant bears), straight-line locomotion, and was likely more adept at pursuing large prey than the extant [[Polar bear|polar]] and [[brown bear]]s.<ref name=":222" /> However, that the limbs are elongated in the proximal rather than distal limb segments, had a plantigrade gait, and a stride which had little to no unsupported intervals, put doubt to this theory.<ref name=":132"/> Moreover, the pronation of the forearm and the flexion of the wrist and digits, and more lightly muscled forelimbs, all of which are crucial to grasping a large prey animal with the forepaws, were probably less powerful in ''Arctodus'' than in either the [[brown bear]] or in ''[[Panthera]].''<ref name=":110" />
[[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|[[American mastodon]] arm bone with ''A.&nbsp;simus'' tooth marks at the [[Denver Museum of Nature & Science]] in [[Denver]], [[Colorado]]]]
[[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|[[American mastodon]] arm bone with ''A.&nbsp;simus'' tooth marks at the [[Denver Museum of Nature & Science]] in [[Denver]], [[Colorado]]]]
[[File:Shortfacedbear-1070375.jpg|thumb|226x226px|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of [[Molar (tooth)|molar]] damage associated with processing bone, [[Tooth decay|dental cavities]], and the lack of specialisation in the [[Canine tooth|canines]], discourages a [[Hypercarnivore|hyper-carnivorous]] interpretation of ''Arctodus''.]]
[[File:Shortfacedbear-1070375.jpg|thumb|226x226px|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of [[Molar (tooth)|molar]] damage associated with processing bone, [[Tooth decay|dental cavities]], and the lack of specialisation in the [[Canine tooth|canines]], discourages a [[Hypercarnivore|hyper-carnivorous]] interpretation of ''Arctodus''.]]
''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by paleontologist Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref>
''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref>


This idea was challenged by a comprehensive review by paleontologist Borja Figueirido and colleagues in 2010,<ref name="Figueiridio_et_al_20102" /> a 2013 study of the micro-wear of the teeth of various extant and extinct bears (examining ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]]), and a 2015 study focusing on [[carnivora]]ns recovered from [[Rancho La Brea]].<ref name="Donohue2">{{cite journal |author1=Donohue, Shelly L. |author2=DeSantis, Larisa R. G. |author3=Schubert, Blaine W. |author4=Ungar, Peter S. |year=2013 |title=Was the giant short-faced bear a hyper-scavenger? A new approach to the dietary study of ursids using dental microwear textures |journal=PLOS ONE |volume=8 |issue=10 |page=e77531 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name=":172">{{Cite journal |last1=DeSantis |first1=Larisa |last2=Schubert |first2=Blaine |last3=Schmitt-Linville |first3=Elizabeth |last4=Ungar |first4=Peter |last5=Donohue |first5=Shelly |last6=Haupt |first6=Ryan |date=2015-01-01 |title=Dental Microwear Textures of Carnivorans from the La Brea Tar Pits, California, and Potential Extinction Implications |url=https://www.researchgate.net/publication/282253545 |journal=La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas |pages=37–52}}</ref> Specialized scavengers like [[hyena]]s show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from [[La Brea Tar Pits|Rancho La Brea]], researchers concluded that ''Arctodus simus'' was not a specialized scavenger. Of living bears, this population of ''A. simus'' showed the most similar tooth wear patterns to its closest living relative, the [[spectacled bear]], which can have a highly varied diet- from obligate omnivory to, on the most part, being almost purely herbivorous in diet.<ref name=":132" /> However, this depends on the region, and seasonal availability.<ref name="Donohue2"/> Additionally, the higher rates of tooth breakage at La Brea were revisited, and due to a relative lack of bone related microwear on other carnivorans (even lower than the modern day) was attributed to the hunting of larger prey, and the acquisition and/or defense of kills.<ref name=":172" /> Moreover, severe tooth crown fractures and alveolar infections were found in the South American giant short faced bear ([[Arctotherium|''Arctotherium'' ''angustidens'']]). These were interpreted as evidence of feeding on tough materials (e.g. bones), which could tentatively indicate for these bears the regular scavenging of ungulate carcasses obtained through [[kleptoparasitism]]. However, such dental pathologies were not observed in the specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_20102" /> Additionally, the short, broad [[Rostrum (anatomy)|rostrum]] of ''Arctodus'' is a characteristic also shared with the [[sun bear]] and the [[spectacled bear]], which are both [[Omnivore|omnivorous]].<ref name="Figueiridio_et_al_20102" /> Moreover, isotope analyses of Beringian ''Arctodus'' specimens suggest that ''Arctodus'' had a low consumption rate of horses and mammoths in Beringia, despite those species making up ~50% of the available biomass in Beringia.<ref name=":312"/>
This idea was challenged by a comprehensive review by paleontologist Borja Figueirido and colleagues in 2010,<ref name="Figueiridio_et_al_20102" /> a 2013 study of the micro-wear of the teeth of various extant and extinct bears (examining ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]]), and a 2015 study focusing on [[carnivora]]ns recovered from [[Rancho La Brea]].<ref name="Donohue2">{{cite journal |author1=Donohue, Shelly L. |author2=DeSantis, Larisa R. G. |author3=Schubert, Blaine W. |author4=Ungar, Peter S. |year=2013 |title=Was the giant short-faced bear a hyper-scavenger? A new approach to the dietary study of ursids using dental microwear textures |journal=PLOS ONE |volume=8 |issue=10 |page=e77531 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name=":172">{{Cite journal |last1=DeSantis |first1=Larisa |last2=Schubert |first2=Blaine |last3=Schmitt-Linville |first3=Elizabeth |last4=Ungar |first4=Peter |last5=Donohue |first5=Shelly |last6=Haupt |first6=Ryan |date=2015-01-01 |title=Dental Microwear Textures of Carnivorans from the La Brea Tar Pits, California, and Potential Extinction Implications |url=https://www.researchgate.net/publication/282253545 |journal=La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas |pages=37–52}}</ref> Specialized scavengers like [[hyena]]s show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from [[La Brea Tar Pits|Rancho La Brea]], researchers concluded that ''Arctodus simus'' was not a specialized scavenger. Of living bears, this population of ''A. simus'' showed the most similar tooth wear patterns to its closest living relative, the [[spectacled bear]], which can have a highly varied diet- from obligate omnivory to, on the most part, being almost purely herbivorous in diet.<ref name=":132" /> However, this depends on the region, and seasonal availability.<ref name="Donohue2"/> Additionally, the higher rates of tooth breakage at La Brea were revisited, and due to a relative lack of bone related microwear on other carnivorans (even lower than the modern day) was attributed to the hunting of larger prey, and the acquisition and/or defense of kills.<ref name=":172" /> Moreover, severe tooth crown fractures and alveolar infections were found in the South American giant short faced bear ([[Arctotherium|''Arctotherium'' ''angustidens'']]). These were interpreted as evidence of feeding on tough materials (e.g. bones), which could tentatively indicate for these bears the regular scavenging of ungulate carcasses obtained through [[kleptoparasitism]]. However, such dental pathologies were not observed in the specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_20102" /> Additionally, the short, broad [[Rostrum (anatomy)|rostrum]] of ''Arctodus'' is a characteristic also shared with the [[sun bear]] and the [[spectacled bear]], which are both [[Omnivore|omnivorous]].<ref name="Figueiridio_et_al_20102" /> Moreover, isotope analyses of Beringian ''Arctodus'' specimens suggest that ''Arctodus'' had a low consumption rate of horses and mammoths in Beringia, despite those species making up ~50% of the available biomass in Beringia.<ref name=":312"/>
Analysis of bones from [[Alaska]] showed high concentrations of [[Isotopes of nitrogen#Nitrogen-15|nitrogen-15]], a stable nitrogen isotope accumulated by carnivores. Additionally, although few specimens exist, there is currently no evidence of the same carbohydrate-related [[Tooth decay|dental pathologies]] evident in southern populations of ''Arctodus simus''.<ref name=":142" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more [[Carnivore|carnivorous]] in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C3 vegetation]], particularly [[Reindeer|caribou]]).<ref name=":312" /><ref name=":412"/> A 2015 study suggests that caribou could not account for the high levels of [[Δ13C|carbon-13]] and [[Nitrogen 15|nitrogen-15]] in some ''Arctodus'' individuals in Beringia. The study suggests that the consumption of [[Muskox|tundra muskox]], which sometimes express high proportions of these isotopes, and possibly other predators in its Beringian range, may explain the data.<ref name=":312" /> Increased carnivory may be due to a lower proportion of competitors and probably a lower availability of carbohydrate-rich food supplies across the year in the far northern latitudes.<ref name=":142" />
Analysis of bones from [[Alaska]] showed high concentrations of [[Isotopes of nitrogen#Nitrogen-15|nitrogen-15]], a stable nitrogen isotope accumulated by carnivores. Additionally, although few specimens exist, there is currently no evidence of the same carbohydrate-related [[Tooth decay|dental pathologies]] evident in southern populations of ''Arctodus simus''.<ref name=":142" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more [[Carnivore|carnivorous]] in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C3 vegetation]], particularly [[Reindeer|caribou]]).<ref name=":312" /><ref name=":412"/> A 2015 study suggests that caribou could not account for the high levels of [[Δ13C|carbon-13]] and [[Nitrogen 15|nitrogen-15]] in some ''Arctodus'' individuals in Beringia. The study suggests that the consumption of [[Muskox|tundra muskox]], which sometimes express high proportions of these isotopes, and possibly other predators in its Beringian range, may explain the data.<ref name=":312" /> Increased carnivory may be due to a lower proportion of competitors and probably a lower availability of carbohydrate-rich food supplies across the year in the far northern latitudes.<ref name=":142" />


Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, the average (700&nbsp;kg) [[Beringia]]n ''Arctodus'' individual needed to consume ~5853&nbsp;kg of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain 100&nbsp;kg of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref>
Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, a {{Convert|700|kg|lb|abbr=on}} [[Beringia]]n ''Arctodus'' would need to consume ~{{Convert|5853|kg|lb}} of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain {{Convert|100|kg|lb|abbr=on}} of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref>


Studies point out that ''A. simus'' would have had a varied diet across its range,<ref name="Donohue2"/> and that the features of the skull and teeth match modern omnivorous bears. Additionally, the isotope data purportedly establishing the carnivory of Beringian ''Arctodus'' overlapped with modern, [[Dietary biology of the brown bear|omni-herbivorous]] brown bears from [[Europe]], eastern [[Wyoming]], and central [[Montana]], demonstrating that isotope data cannot distinguish between [[hypercarnivore]]s and [[omnivore]]s which eat a significant amount of animal matter.<ref name=":110" /> However, this has been challenged on the basis that herbivory should be more obvious in the data gathered from ''Arctodus''.<ref name=":332" />
Studies point out that ''A. simus'' would have had a varied diet across its range,<ref name="Donohue2"/> and that the features of the skull and teeth match modern omnivorous bears. Additionally, the isotope data purportedly establishing the carnivory of Beringian ''Arctodus'' overlapped with modern, [[Dietary biology of the brown bear|omni-herbivorous]] brown bears from [[Europe]], eastern [[Wyoming]], and central [[Montana]], demonstrating that isotope data cannot distinguish between [[hypercarnivore]]s and [[omnivore]]s which eat a significant amount of animal matter.<ref name=":110" /> However, this has been challenged on the basis that herbivory should be more obvious in the data gathered from ''Arctodus''.<ref name=":332" />

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Old page wikitext, before the edit (old_wikitext)
'{{Short description|Extinct genus of bears}} {{Automatic taxobox | fossil_range = [[Pleistocene]], {{fossil range|2.5|0.012}} | image = Arctodus simus Page.jpg | image_caption = ''A. simus'' from the [[La Brea tar pits]] | taxon = Arctodus | authority = [[Joseph Leidy|Leidy]], 1854 | type_species = {{extinct}}'''''Arctodus pristinus''''' | type_species_authority = [[Joseph Leidy|Leidy]], 1854 | subdivision_ranks = Other species | subdivision = *{{extinct}}'''''A. simus''''' <small>([[Edward Drinker Cope|Cope]], 1879)</small> | range_map = Short Faced Bear Range.png | range_map_caption = ''Arctodus simus'' range | synonyms = {{collapsible list|bullets=true|title=Species synonymy |{{collapsible list|bullets=true|title=''A. simus'': |''[[Arctotherium]] californicum'' {{small|[[John Campbell Merriam|Merriam]] 1911}} |''Arctotherium simum'' {{small|[[Edward Drinker Cope|Cope]] 1879}} |''Arctotherium yukonense'' {{small|[[Lawrence Lambe|Lambe]] 1911}} |''Dinarctotherium merriami'' {{small|[[Erwin Hinckley Barbour|Barbour]] 1916}} |''Tremarctotherium simum'' {{small|[[James W. Gidley|Gidley]] 1928}} }} |{{collapsible list|bullets=true|title=''A. pristinus'': |''Arctodus haplodon'' {{small|[[Oliver Perry Hay|Hay]] 1902}} |''[[Arctotherium]] pristinum'' {{small|[[Edward Drinker Cope|Cope]] 1895}} |''[[Ursus]] haplodon'' {{small|[[Edward Drinker Cope|Cope]] 1896}} |''[[Tremarctos]] haplodon'' {{small|[[Édouard Louis Trouessart|Trouessart]] 1897}} }} }} }}'''''Arctodus''''' is an extinct genus of [[short-faced bear]] that inhabited [[North America]] during the [[Pleistocene]] (~2.5 [[Year#mya|Mya]] until 12,000 years ago). There are two recognized species: the '''lesser short-faced bear''' (''Arctodus pristinus'') and the '''giant short-faced bear''' (''Arctodus simus''). Both species are relatively rare in the fossil record- ''A. pristinus'' was largely restricted to the Early Pleistocene of the eastern United States, whereas ''A. simus'' had a cosmopolitan range, with most finds being from the Late Pleistocene of the US, Mexico and Canada. ''A. simus'' evolved from ''A. pristinus'', but both species likely overlapped in the Middle Pleistocene. Of these species, ''A. simus'' was larger, is known from more complete remains, and is considered one of the most charismatic of North America's megafauna. Today considered to be an enormous omnivore, ''Arctodus simus'' is believed to be one of the largest known terrestrial mammalian [[carnivora]]ns that has ever existed. However, ''Arctodus'', like other bears, was highly sexually dimorphic. Adult ''A. simus'' ranged between 300&nbsp;kg to 950&nbsp;kg, with females clustering at ≤500&nbsp;kg, and males around 800&nbsp;kg. The largest males stood at 1.5 meters at the shoulder, and up to 3 meters tall on their rear legs. Studies suggest that ''Arctodus simus'' both browsed on vegetation and consumed browsing herbivores, such as [[deer]], [[Camelidae|camelids]], and [[Tapirus|tapir]]. ''A. simus'' seems to have preferred open woodlands, but was an adaptable species, taking advantage of many habitats and feeding opportunities. ''Arctodus'' belongs to the [[Tremarctinae]] subfamily of bears, which are endemic to the [[Americas]]. Of these short-faced bears, ''Arctodus'' was the most widespread in North America. However, both species went extinct in the Pleistocene. ''A. pristinus'' went extinct around 300,000 years ago, with ''A. simus'' disappearing ~12,000 years ago in the [[Quaternary extinction event]], being one of the last recorded megafauna to go extinct in North America. The cause behind these extinctions is unclear, but in the case of ''A. pristinus'', this was likely due to climate change and competition with other ursids, such as the [[American black bear|black bear]] and ''[[Tremarctos floridanus]]''. ''A. simus'' likely went extinct due to ecological collapse disrupting the vegetation and prey ''A. simus'' relied on. ==Taxonomy== ''Arctodus'' was first described by [[Joseph Leidy]] in 1854, with finds of ''A. pristinus'' from the [[Northbridge Park|Ashley Phosphate Beds]], [[South Carolina]].<ref name=":262">{{Cite web |date=2017-03-30 |title=Arctodus pristinus |url=https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/arctodus-pristinus/ |access-date=2022-02-21 |website=Florida Museum |language=en-US}}</ref><ref name=":5" /><ref>{{Cite journal |date=1879-08-01 |title=South Carolina Fossils |url=https://www.nature.com/articles/020354a0 |journal=Nature |language=en |volume=20 |issue=510 |pages=354–355 |doi=10.1038/020354a0 |bibcode=1879Natur..20..354. |s2cid=4034608 |issn=1476-4687}}</ref> The scientific name of the genus, ''Arctodus'', derives from [[Greek language|Greek]], and means "bear tooth". The first fossils of ''A. simus'' were found in the Potter Creek Cave, [[Shasta County, California|Shasta County]], [[California]], by J. A. Richardson in 1878, and were described by [[Edward Drinker Cope]] in 1879.<ref name=":48">{{Cite journal |last=Cope E. D. |year=1879 |title=The cave bear of California |journal=American Naturalist |volume=13 |page=791}}</ref><ref>{{Cite journal |last=Feranec |first=Robert S. |date=2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |journal=Radiocarbon |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |doi-access=free }}</ref><ref>{{Citation |last1=Merriam |first1=John C. |title=Relationships and Structure of the Short-Faced Bear, Arctotherium, from the Pleistocene of California |date=1925 |url=https://resolver.caltech.edu/CaltechAUTHORS:20191008-132308406 |pages=1–25 |place=Washington, DC |publisher=Carnegie institution of Washington |language=en |access-date=2022-05-06 |last2=Stock |first2=Chester}}</ref> The most nearly complete skeleton of ''A. simus'' found in the [[United States|US]] was unearthed in [[Fulton County, Indiana|Fulton County]], [[Indiana]]; the original bones are in the [[Field Museum of Natural History]], [[Chicago]].<ref name=":39">{{Cite book |last1=Richards |first1=Ronald L. |url=https://www.biodiversitylibrary.org/bibliography/3480 |title=Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, northern Indiana |last2=Neiburger |first2=Ellis J. |last3=Turnbull |first3=William D. |date=1995 |publisher=Field Museum of Natural History |location=Chicago, Ill. }}</ref><ref>{{Cite book |last=Stark |first=Mike |url=https://books.google.com/books?id=hWhgEAAAQBAJ&dq=field+museum+rochester+arctodus&pg=PA122-IA12 |title=Chasing the Ghost Bear: On the Trail of America's Lost Super Beast |date=2022 |publisher=U of Nebraska Press |isbn=978-1-4962-2902-1 |pages=Fig. 19 }}</ref> In the 19th and early 20th centuries, specimens of ''Arctodus'' were occasionally referred to ''[[Arctotherium]]'', and vice versa.<ref>{{Cite web |title=Arctodus |url=https://www.utep.edu/leb/pleistnm/taxaMamm/Arctodus.htm#:~:text=Synonyms.,Arctotherium%20simum,%20Tremarctotherium%20simum |access-date=2022-05-05 |website=www.utep.edu}}</ref><ref>{{Cite book |last1=Spamer |first1=Earle E. |url=https://books.google.com/books?id=3loD7lTLBxgC&dq=Arctodus+haplodon&pg=PA204 |title=A Study of Fossil Vertebrate Types in the Academy of Natural Sciences of Philadelphia: Taxonomic, Systematic, and Historical Perspectives |last2=Daeschler |first2=Edward |last3=Philadelphia |first3=Academy of Natural Sciences of |last4=Vostreys-Shapiro |first4=L. Gay |date=1995 |publisher=Academy of Natural Sciences |isbn=978-0-910006-51-4 |language=en}}</ref><ref>{{Cite book |last=Hay |first=Oliver Perry |url=https://books.google.com/books?id=mkMZAAAAYAAJ&q=haplodon&pg=PA763 |title=Bibliography and Catalogue of the Fossil Vertebrata of North America |date=1901 |publisher=U.S. Government Printing Office |language=en}}</ref><ref>{{Citation |last1=Merriam |first1=John C. |title=Relationships and Structure of the Short-Faced Bear, Arctotherium, from the Pleistocene of California |date=1925 |url=https://resolver.caltech.edu/CaltechAUTHORS:20191008-132308406 |pages=1–25 |place=Washington, DC |publisher=Carnegie institution of Washington |language=en |access-date=2022-06-09 |last2=Stock |first2=Chester}}</ref> However, today neither genera are considered to have overlapped, with the closest point of contact being [[Mexico|México]]; the giant ''Arctodus simus'' in [[Hueyatlaco|Valsequillo]], [[Puebla]], and the smaller ''[[Arctotherium|Arctotherium wingei]]'' in the [[Yucatán Peninsula]].<ref name=":352">{{Cite journal |last1=Ferrusquía-Villafranca |first1=Ismael |last2=Arroyo-Cabrales |first2=Joaquín |last3=Martínez-Hernández |first3=Enrique |last4=Gama-Castro |first4=Jorge |last5=Ruiz-González |first5=José |last6=Polaco |first6=Oscar J. |last7=Johnson |first7=Eileen |date=2010-04-15 |title=Pleistocene mammals of Mexico: A critical review of regional chronofaunas, climate change response and biogeographic provinciality |url=https://www.sciencedirect.com/science/article/pii/S104061820900442X |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |language=en |volume=217 |issue=1 |pages=53–104 |doi=10.1016/j.quaint.2009.11.036 |bibcode=2010QuInt.217...53F |issn=1040-6182}}</ref><ref>{{Cite journal |last1=Arroyo-Cabrales |first1=Joaquín |last2=Polaco |first2=Oscar J. |last3=Johnson |first3=Eileen |last4=Ferrusquía-Villafranca |first4=Ismael |date=2010-02-01 |title=A perspective on mammal biodiversity and zoogeography in the Late Pleistocene of México |url=https://www.sciencedirect.com/science/article/pii/S1040618209001633 |journal=Quaternary International |series=Quaternary Changes of Mammalian Communities Across and Between Continents |language=en |volume=212 |issue=2 |pages=187–197 |doi=10.1016/j.quaint.2009.05.012 |bibcode=2010QuInt.212..187A |issn=1040-6182}}</ref><ref name=":25" /> Conversely, fossils of ''Arctodus pristinus'' are often confused with the similarly sized, partially contemporaneous [[Tremarctinae|short-faced bear]], ''Tremarctos floridanus''.<ref name=":262"/> Sometimes described as the "American cave bear", ''Arctodus'' should not be mistaken for the similarly large [[Cave bear|Eurasian cave bear]] (''Ursus speleaus'').<ref name=":48" /> As an ursine, the Eurasian cave bear last shared a common ancestor with the tremarctine ''Arctodus'' circa 13.4 million years ago.<ref name="Pedersen 2728–2736.e8" /> ===Evolution=== {{Cladogram|{{clade| style=font-size:90%;line-height:90%; |1={{dagger}}[[Hemicyoninae]] |2={{Clade |1={{dagger}}[[Ursavinae]] |2={{Clade |1={{dagger}}[[Agriotheriinae]] |2={{Clade |1=[[Ailuropodinae]] [[File:Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg|75px]] |2={{Clade |1=[[Ursinae]] [[File:Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|75px]] |2={{Clade |label1=[[Tremarctinae]] (short-faced bears) |1={{Clade |1={{dagger}}''[[Plionarctos]]'' |2={{Clade |1={{dagger}}'''''Arctodus''''' |2={{Clade |1=''[[Tremarctos]]'' [[File:Spectacled bear (1829).jpg|75px]] |2={{dagger}}''[[Arctotherium]]'' }} }} }} }} }} }} }} }} }}|title=[[Tremarctinae]] within [[Ursidae]]|align=left}} ''Arctodus'' belongs to a group of bears known as the short-faced bears ([[Tremarctinae]]), which appeared in [[North America]] during the earliest parts of the late [[Miocene]] epoch in the form of ''[[Plionarctos]]'', a genus considered ancestral to Tremarctinae. ''[[Plionarctos]]'' gave way to the medium-sized ''Arctodus pristinus,'' ''Tremarctos floridanus'' and ''Arctotherium sp.'' in the [[Blancan|Blancan age]] of [[North America]],<ref name=":5">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |s2cid=168164209 }}</ref><ref name=":18">{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Romero |first2=M.R. Aguilar |date=2008-10-14 |title=A Blancan (Pliocene) short-faced bear from El Salvador and its implications for Tremarctines in South America |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=250 |issue=1 |pages=1–8 |doi=10.1127/0077-7749/2008/0250-0001 |url=http://sedici.unlp.edu.ar/handle/10915/5361 }}</ref><ref name=":02">{{Cite journal |last1=Schubert |first1=Blaine |last2=Hulbert |first2=Richard |last3=MacFadden |first3=Bruce |last4=Searle |first4=Michael |last5=Searle |first5=Seina |date=2010-01-01 |title=Giant Short-faced Bears (Arctodus simus) in Pleistocene Florida USA, a Substantial Range Extension |url=https://www.researchgate.net/publication/250071137 |journal=Journal of Paleontology |volume=84 |pages=79–87 |doi=10.1666/09-113.1 |s2cid=131532424}}</ref> with the genetic divergence date for ''Arctodus'' being ~5.5 million years ago.<ref name="Pedersen 2728–2736.e8" /> Both ''Arctodus'' and ''[[Tremarctos]]'' were largely restricted to the more forested eastern part of the continent, as ''[[Borophagus|Boropahgus]]'' and ''[[Agriotherium]]'' are thought to have limited [[Tremarctinae|tremarctine]] presence in the more open Western [[North America]]. ''Tremarctos floridanus'' established a range mostly hugging the [[Gulf of Mexico|Gulf Coast]] (but also extending to [[California]], [[Idaho]] and [[Belize]]),<ref name=":02"/> whereas ''Arctodus pristinus'' ranged from [[Aguascalientes]], Mexico,<ref>{{Cite journal |last1=Dalquest |first1=W. W. |last2=Mooser |first2=O. |date=1980-12-19 |title=Arctodus pristinus Leidy in the Pleistocene of Aguascalientes, Mexico |journal=Journal of Mammalogy |volume=61 |issue=4 |pages=724–725 |doi=10.2307/1380320 |jstor=1380320 }}</ref> to [[Port Kennedy Bone Cave|Port Kennedy]], Pennsylvania, in the US.<ref name="researchgate.net">{{Cite journal |last1=Daeschler |first1=Edward B. |last2=Spamer |first2=Earl E. |last3=Parris |first3=David C. |date=1993 |title=Review and New Data on the Port Kennedy Local Fauna and Flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania |url=https://www.researchgate.net/publication/325630951 |journal=The Mosasaur - Delaware Valley Paleontological Society |volume=5 |pages=23–41 |via=ResearchGate}}</ref> Perhaps due to their evolutionary history, both ''[[Tremarctos floridanus]]'' and ''Arctodus pristinus'' have the greatest concentration of fossils in [[Florida]]- ''A. pristinus'' is first known from the [[Santa Fe River (Florida)|Santa Fe River 1 site]] of [[Gilchrist County, Florida|Gilchrist County]]. However, in the [[Quaternary|early Quaternary]], when both ''[[Borophagus]]'' and ''[[Agriotherium]]'' went extinct, ''Arctodus'' would take advantage and spread into the rest of the continent, primarily in the form of ''A. simus''. Concurrently, during the [[Great American Interchange]] that followed the joining of North and South America, the [[Central America]]n based ''Arctotherium'' invaded [[South America]],<ref name=":18" /> leading to the diversification of the genus, including the colossal ''[[Arctotherium|Arctotherium angustidens]]''. During the early [[Irvingtonian]] (~1.1 million years ago), the smaller ''A. pristinus'' was joined by the enormous ''A. simus''.<ref>{{Cite book |last1=Bell |first1=Christopher |url=https://www.researchgate.net/publication/263425514 |title=Late Cretaceous and Cenozoic Mammals of North America |last2=Lundelius |first2=Ernest L. |last3=Barnosky |first3=Anthony D. |last4=Zarzewski |first4=Richard J. |last5=Graham |first5=Russell |last6=Lindsay |first6=Everett H. |last7=Ruez |first7=Dennis R. |last8=Semken |first8=Holmes A. |last9=Webb |first9=S. David |date=2004-04-21 |publisher=Columbia University Press |isbn=978-0-231-50378-5 |language=en |chapter=Chapter 7: The Blancan, Irvingtonian, and Rancholabrean Mammal Ages |doi=10.7312/wood13040}}</ref> The two are differentiated not only by size, but also by the shorter snout, more robust teeth and longer limbs of ''A. simus,'' and the relative proportions of each species' molars and premolars. However, there are relatively few morphological differences. As a result, differentiating ''Arcotdus simus'' from ''Arctodus pristinus'' can be difficult, as large individuals of ''Arctodus pristinus'' can overlap in size with small individuals of ''Arctodus simus''.<ref name=":02"/> ''A. simus'' is first recorded from the Irvington type locality in California. Although both species co-existed for at least half a million years (''A. pristinus'' went extinct ~300,000 BP), there is no direct evidence of [[sympatry]] or [[Competition (biology)|competition]] in the fossil record as of yet.<ref name=":02"/> However, there are unreliable records of ''A. pristinus'' in [[South Carolina]], [[California]] and [[Florida]] in the [[Late Pleistocene]], suggesting a possible existence as a [[Relict (biology)|relict species]] in [[Refugium (population biology)|refugia]] until the [[Quaternary extinction|Quaternary extinction event]].<ref>{{Cite journal |last1=Feranec |first1=Robert S. |last2=Hadly |first2=Elizabeth A. |last3=Blois |first3=Jessica L. |last4=Barnosky |first4=Anthony D. |last5=Paytan |first5=Adina |date=2007 |title=Radiocarbon Dates from the Pleistocene Fossil Deposits of Samwel Cave, Shasta County, California, USA |journal=Radiocarbon |volume=49 |issue=1 |pages=117–121 |doi=10.1017/S0033822200041941 |s2cid=130708736 |doi-access=free }}</ref><ref name=":8">{{Cite book |last=Sanders |first=Albert E. |url=https://books.google.com/books?id=LS8LAAAAIAAJ&dq=pristinus+south+carolina&pg=PA48 |title=Additions to the Pleistocene Mammal Faunas of South Carolina, North Carolina, and Georgia |date=2002 |publisher=American Philosophical Society |isbn=978-0-87169-925-1 }}</ref><ref name=":92">{{Cite web |last1=Esker |first1=Donald |last2=Wilkins |first2=William |last3=Agenbroad |first3=Larry |date=2010-08-13 |title=Esker, Wilkins, and Agenbroad—Multivariate Analysis Of Ursids: A multivariate analysis of the ecology of North American Pleistocene bears, with a focus on ''Arctodus simus'' |website=ResearchGate |url=https://www.researchgate.net/publication/314037201}}</ref> Likewise, ''Arctodus simus'' is relatively poorly known from the [[Irvingtonian]] (1,900,000 BP-250,000 BP) with finds mostly from California, with additional remains from Texas, Kansas, Nebraska, and Montana.<ref name=":46" /><ref name=":4" /> In any case, whereas ''A. pristinus'' seems to have preferred the more heavily forested thermal enclave in eastern North America,<ref name=":10">{{Cite journal |last1=Russell |first1=Dale A. |last2=Rich |first2=Fredrick J. |last3=Schneider |first3=Vincent |last4=Lynch-Stieglitz |first4=Jean |date=May 2009 |title=A warm thermal enclave in the Late Pleistocene of the South-eastern United States |journal=Biological Reviews |volume=84 |issue=2 |pages=173–202 |doi=10.1111/j.1469-185X.2008.00069.x |pmid=19391200 |s2cid=9609391 }}</ref> ''A. simus'' was a cosmopolitan, eventually pan-continental species in the Late Pleistocene- sharing that distinction with the [[American black bear|black bear]], and the [[brown bear]] after 100,000 BP.<ref name=":92"/> Primarily inhabiting a range from southern [[Canada]] to [[Puebla|Central Mexico]] in the west, to [[Pennsylvania]] and [[Florida]] in the east,<ref name=":25">{{Cite book|last1=Richards|first1=Ronald L. |title=Distribution and size variation in North American Short-faced bears, Arctodus simus|last2=Churcher|first2=C. S.|last3=Turnbull|first3=William D.|date=2019-11-18|publisher=University of Toronto Press|isbn=978-1-4875-7415-4 |doi=10.3138/9781487574154-012}}</ref><ref name=":02"/><ref>{{Cite journal |last1=Steffen |first1=Martina L. SteffenM L. |last2=Harington |first2=C. R. HaringtonC R. |date=2010-07-23 |title=Giant short-faced bear (Arctodus simus) from late Wisconsinan deposits at Cowichan Head, Vancouver Island, British Columbia |url=https://cdnsciencepub.com/doi/abs/10.1139/E10-018 |journal=Canadian Journal of Earth Sciences |volume=47 |issue=8 |pages=1029–1036 |language=en |doi=10.1139/E10-018|bibcode=2010CaJES..47.1029S }}</ref><ref>{{Cite journal |last=Cassiliano M. L. |year=1999 |title=Biostratigraphy of Blancan and Irvingtonian mammals in the Fish Creek-Vallecito Creek section, southern California, and a review of the Blancan-Irvingtonian boundary |journal=Journal of Vertebrate Paleontology |volume=19 |issue=1 |pages=169–186 |doi=10.1080/02724634.1999.10011131}}</ref><ref>{{cite journal |last1=Carranza-Castañeda |first1=Oscar |last2=Miller |first2=Wade E. |title=Rediscovered type specimens and other important published Pleistocene mammalian fossils from Central Mexico |journal=Journal of Vertebrate Paleontology |date=16 September 1987 |volume=7 |issue=3 |pages=335–341 |doi=10.1080/02724634.1987.10011664 }}</ref><ref name=":24">{{Cite journal |last1=Holliday |first1=Vance |last2=Surovell |first2=Todd |last3=Meltzer |first3=David |last4=Grayson |first4=Donald |last5=Boslough |first5=Mark |date=2014-08-01 |title=The Younger Dryas impact hypothesis: A cosmic catastrophe |url=https://www.researchgate.net/publication/265132201 |journal=Journal of Quaternary Science |volume=29 |issue=6 |pages=515–530 |doi=10.1002/jqs.2724|bibcode=2014JQS....29..515H |s2cid=18644154 }}</ref> ''A. simus'' is particularly famous from fossils found in the [[La Brea tar pits]] in southern [[California]].<ref name="Bearalmanac">{{Cite book |last=Brown, Gary |url=https://archive.org/details/greatbearalmanac00gary/page/340 |title=Great Bear Almanac |year=1996 |isbn=978-1558214743 |page=[https://archive.org/details/greatbearalmanac00gary/page/340 340] |url-access=registration}}</ref> From ~50,000 BP to ~23,000 BP, ''A. simus'' also inhabited [[Beringia]]- finds today span from northern [[Alaska]] to the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /><ref name=":02"/><ref name=":24" /><ref>C. S. Churcher, A. V. Morgan, and L. D. Carter. 1993. ''Arctodus simus from the Alaskan Arctic Slope''. Canadian Journal of Earth Sciences 30(5):1007-1013, collected by A. V. Morgan</ref> The [[Late Pleistocene]] represents the peak of [[Bear|ursid]] diversity in [[Quaternary]] [[North America]], with ''Arctodus simus,'' [[brown bear]]s, [[American black bear|black bears]], ''[[Tremarctos floridanus]]'', and ''[[Arctotherium|Arctotherium wingei]]'' all roaming south of the [[Laurentide Ice Sheet]],<ref name=":19">{{cite bioRxiv |last1=Salis |first1=Alexander T |last2=Bray |first2=Sarah C E |last3=Lee |first3=Michael S Y |last4=Heiniger |first4=Holly |last5=Barnett |first5=Ross |last6=Burns |first6=James A |last7=Doronichev |first7=Vladimir |last8=Fedje |first8=Daryl |last9=Golovanova |first9=Liubov |last10=Harington |first10=C Richard |last11=Hockett |first11=Bryan |last12=Kosintsev |first12=Pavel |last13=Lai |first13=Xulong |last14=Mackie |first14=Quentin |last15=Vasiliev |first15=Sergei |last16=Weinstock |first16=Jacobo |last17=Yamaguchi |first17=Nobuyuki |last18=Meachen |first18=Julie |last19=Cooper |first19=Alan |last20=Mitchell |first20=Kieren J |title=Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge |date=3 September 2020 |biorxiv=10.1101/2020.09.03.279117}}</ref><ref>{{Cite journal|last1=Schubert|first1=Blaine W.|last2=Chatters|first2=James C.|last3=Arroyo-Cabrales|first3=Joaquin|last4=Samuels|first4=Joshua X.|last5=Soibelzon|first5=Leopoldo H.|last6=Prevosti|first6=Francisco J.|last7=Widga|first7=Christopher|last8=Nava|first8=Alberto|last9=Rissolo|first9=Dominique|last10=Erreguerena|first10=Pilar Luna|date=May 2019|title=Yucatán carnivorans shed light on the Great American Biotic Interchange|journal=Biology Letters|volume=15|issue=5|pages=20190148|doi=10.1098/rsbl.2019.0148 |pmc=6548739|pmid=31039726}}</ref> and [[polar bear]]s above the ice.<ref>{{Cite journal|last1=Arroyo-Cabrales|first1=Joaquin|last2=Johnson|first2=Eileen|last3=Graham|first3=Ruswell|last4=perez crespo|first4=Victor|date=2016-07-24|title=North American ursid (Mammalian: Ursidae) defaunation from Pleistocene to recent.|url=https://www.researchgate.net/publication/305681538|journal=Cranium|volume=33|pages=51–56}}</ref><ref name=":112">{{Cite book |last=Pérez-Crespo |first=J. Arroyo-Cabrales E. Johnson R.W. Graham V.A. |title=North American ursid (mammalia: ursidae) defaunation from Pleistocene to recent |date=2016-01-01 |oclc=1227719621}}</ref> However, despite ''Arctodus simus''<nowiki/>' large temporal and geographic range, fossil remains are comparatively rare (109 finds as of 2010, in otherwise well-sampled localities).<ref name=":02"/><ref name="Pedersen 2728–2736.e8">{{Cite journal|last1=Pedersen|first1=Mikkel Winther|last2=De Sanctis|first2=Bianca|last3=Saremi|first3=Nedda F.|last4=Sikora|first4=Martin|last5=Puckett|first5=Emily E.|last6=Gu|first6=Zhenquan|last7=Moon|first7=Katherine L.|last8=Kapp|first8=Joshua D.|last9=Vinner|first9=Lasse|last10=Vardanyan|first10=Zaruhi|last11=Ardelean|first11=Ciprian F.|date=2021-06-21|title=Environmental genomics of Late Pleistocene black bears and giant short-faced bears |journal=Current Biology |volume=31|issue=12|pages=2728–2736.e8|doi=10.1016/j.cub.2021.04.027|pmid=33878301|s2cid=233303447 |hdl=10037/22808|hdl-access=free}}</ref> === Genetic diversity === An examination of mitochondrial DNA sequenced from specimens of ''Arctodus simus'' from Alaska, Yukon, Alberta and Ohio suggest an extremely low level of genetic diversity among the 23 individuals studied (≤ 44,000 [[Radiocarbon dating|<sup>14</sup>C]] BP), with only seven haplotypes recovered, forming a monophyletic clade. Genetic diversity was comparable to modern endangered taxa, such as the brown kiwi and African cheetah. Explanations include a [[Population bottleneck|genetic bottleneck]] before 44,000 <sup>14</sup>C BP, or a low level of genetic diversity being a feature of a species which was primarily solitary, with a large home range and relatively small population size. However, a similar lack of genetic diversity across large geographic areas can be found in some hyenas in Africa, such as the [[striped hyena]] and [[brown hyena]].<ref name=":49" /> However, this does not entirely preclude genetic diversity in ''Arctodus simus'', with genetic samples from [[Chiquihuite cave]], Mexico (~14,000 BP), indicating a deep divergence with previously studied specimens of ''A. simus''.<ref name="Pedersen 2728–2736.e8" /> ==Description== === Size === [[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and 317&nbsp;kg, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" /> Though over 100 giant short-faced bear localities in [[North America]] are known, only one site produced a [[baculum]] (penis bone) that could belong to ''Arctodus simus''. The lack of recovered ''Arctodus'' [[Baculum|bacula]] likely reflects both [[taphonomy]] and behaviour. The majority of skeletal remains representing large individuals are from open sites where usually only a few elements were recovered. In contrast, horizontal (walk-in) cave passages produced numerous examples of small, yet relatively complete individuals where [[Baculum|bacula]] would likely be found if they had been present. Both the small size of recovered skeletal elements and the lack of [[Baculum|bacula]] from cave deposits suggest that female individuals of ''A. simus'' were using caves, in line with [[Bear|ursid]] maternal denning.<ref name=":2">{{Cite journal|last1=CHUBERT|first1=BLAINE|last2=KAUFMANN|first2=JAMES|date=2003-08-01|title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species|url=https://www.researchgate.net/publication/252748398|journal=Journal of Cave and Karst Studies|volume=65}}</ref><ref name=":3">{{Cite journal|last1=Fowler|first1=Nicholas L.|last2=Spady|first2=Thomas J.|last3=Wang|first3=Guiming|last4=Leopold|first4=Bruce D.|last5=Belant|first5=Jerrold L.|date=October 2021|title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51|issue=4|pages=465–481|doi=10.1111/mam.12246|s2cid=233847639 }}</ref> Therefore, in conjunction with ursid sexual dimorphism (e.g. in [[spectacled bear]]s, males are 30%-40% larger than females), the largest individuals are often considered male, particularly older males, with the smaller individuals being females.<ref name=":02"/><ref name=":12">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |doi=10.1016/j.quaint.2009.11.010 |bibcode=2010QuInt.217..188S }}</ref><ref name=":46">{{Cite journal |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |journal=PaleoBios |volume=15 |issue=2 |pages=27–36 |date=May 24, 1993 |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf}}</ref> Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~555&nbsp;kg.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1994 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~372&nbsp;kg, smaller than recovered [[brown bear]] remains (~455&nbsp;kg, although these remains may postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~770&nbsp;kg from six specimens.<ref name=":7" /> Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between 1,200&nbsp;kg and 412&nbsp;kg,<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between 957&nbsp;kg (~1,000&nbsp;kg) and 317&nbsp;kg.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref> === Data === Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]].<ref name=":6" /><ref name=":62"/> Also included are the mean figures from [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref> {| class="wikitable sortable" |+ !Element ID & Location !Proximal Length (mm) !Total Length (mm) !Transverse Width (midshaft, mm) !Ratio of TL to TW (M) x 100 !Standard Deviation !Number |- |P.89.13.91, [[Edmonton]] |585 |707 (est.) |63.2 |9.0 |~ |1 |- |UVP 015/1, Utah |598 |723 |64 |8.9 |~ |1 |- |UC 3721, [[Shasta Lake|Potter Creek Cave]] |~ |524 |43.3 |8.3 |~ |1 |- |F:AM 25531, [[Hay Springs, Nebraska|Hay Springs]] |~ |658 |62.6 |9.5 |~ |1 |- |UM 25611, [[Meade, Kansas|Jinglebob]] |~ |507 |43.3 |8.5 |~ |1 |- |UC 44687, [[Irvington, California|Irvington]] |~ |678 |62 |9.1 |~ |1 |- |LACMNH-Z75, [[La Brea Tar Pits|Rancho La Brea]] |444 |~ |42.3 |~ |~ |1 |- |U.S.A. sites, x̄ values (Kurtén, 1967) |~ |584 |47.8 |8.1-9.5 (x̄= 8.7) |0.45 |9 |} === Anatomy === ==== Skull ==== [[File:Arctodus simus skull Cleveland.jpg|thumb|''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], [[Ohio]]]] Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] are likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" /> The skull also has a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance; this broad [[snout]] possibly housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas (although this is characteristic shared with the omni-herbivorous spectacled bear).<ref name=":7" /><ref name=":132">{{Cite journal |last1=Emslie |first1=Steven D. |last2=Czaplewski |first2=Nicholas J. |date=1985-11-15 |title=A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology |url=https://www.biodiversitylibrary.org/partpdf/226835 |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793}}</ref><ref name=":402">{{Cite journal |last=Matheus |first=Paul E. |date=1995-11-01 |title=Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0033589485710903 |journal=Quaternary Research |language=en |volume=44 |issue=3 |pages=447–453 |doi=10.1006/qres.1995.1090 |bibcode=1995QuRes..44..447M |s2cid=83542760 |issn=0033-5894}}</ref><ref>{{Cite journal |last1=Goswami |first1=Anjali |last2=Milne |first2=Nick |last3=Wroe |first3=Stephen |date=2011-06-22 |title=Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1713 |pages=1831–1839 |doi=10.1098/rspb.2010.2031 |issn=0962-8452 |pmc=3097826 |pmid=21106595}}</ref> The [[Orbit (anatomy)|orbits]] of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat [[Lateral (anatomy)|laterally orientated]] (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the [[brown bear]], suggesting that [[Stereopsis|stereoscopic vision]] was not a priority.<ref name=":110"/><ref name=":302"/><ref name=":292">{{Cite book |last=Baryshnikov |first=Gennady |url=https://www.researchgate.net/publication/336916777 |title=The Hot Springs Mammoth Site: A Decade of Field and Laboratory Research in Paleontology, Geology and Paleoecology |publisher=The Mammoth Site of Hot Springs, South Dakota Inc. |year=1994 |editor-last=Agenbroad |editor-first=Larry D. |pages=Chapter 16 |editor-last2=Mead |editor-first2=Jim I.}}</ref> The [[premolar]]s and [[Molar (tooth)|first molars]] of ''Arctodus pristinus'' are relatively smaller and more widely spaced than those of ''Arctodus simus''. However, the morphologies of both species are otherwise very similar. Differentiating between the two can be difficult, as males of ''A. pristinus'' overlap in size with females of ''A. simus''.<ref name=":262"/><ref name=":02"/> The dentition of ''Arctodus'' has been used as evidence of a predatory lifestyle- in particular the large [[Canine tooth|canines]], the high-crowned lower [[first molar]], and the possible [[carnassial shear]] with the upper [[Premolar|fourth premolar]]. However, the wearing of the molars to a relatively flat, blunt loph (suitable as a crushing platform as per modern omnivorous bears), small shear facet, and the flattened [[Cusp (anatomy)|cusps]] across age ranges (unlike carnivores, which instead have [[carnassial shear]]s) suggests an alternative adaptive purpose.<ref name=":132"/> In ''A. pristinus'', the features of the dentition can be quite variable, particularly the M2 molar.<ref name=":5" /> A specimen of ''A. simus'' from the Seale Pit of the Hill-Shuler locality, Texas, with only two premolars, crowding of the anterior premolar out of line, and a wider and shorter muzzle, was even suggested to be an undescribed form of ''Arctodus''.<ref name=":13" /> An analysis of the [[Mandible|mandibular]] morphology of tremarctine bears found that ''Arctodus pristinus'' and ''Arctodus simus'' were divergent in the dimensions of their cranial anatomy, with ''Arctodus simus'' clustering tightly with ''Arctotherium angustidens'', suggesting a similar foraging strategy. ''A. simus'' specimens have a concave jaw, large [[Masseter muscle|masseter]] and [[Temporalis muscle|temporalis]] muscles, deeper horizontal ramus and a reduced slicing dentition length, when compared to ''A. pristinus''. However, both ''A. pristinus'' and ''A. simus'' were still found to be comfortably in the "omnivorous" bear cranio-morphotype, and are interpreted as such, along with ''Arctotherium angustidens''.<ref name=":302"/> ==== Post-cranial ==== [[File:ArctodusSimusReconstruct.jpg|thumb|''A. simus'' compared with a human|left]] Although the shape of the [[Elbow|elbow joint]] suggests ''Arctodus'', ''[[Arctotherium|Arctotherium bonariense]]'', and ''[[Arctotherium|Arctotherium wingei]]'' had the possibility of retaining [[Arboreal locomotion|semi-arboreal]] adaptations, the size of the elbow joint condemns ''Arctodus'' to terrestrial life. As the [[Medial epicondyle of the humerus|medial epicondyle]] is particularly expanded in these species, it is likely that ''Arctodus'' and ''Arctotherium'' (just like the [[giant panda]]) retained this characteristic to attain a higher degree of forelimb dexterity. Whether this dexterity facilitated [[Scavenger|scavenging]] or [[Herbivore|herbivory]], this high degree of proximal dexterity was probably advantageous for these species, and retained in tremarctine bears despite their general tendency towards terrestriality.<ref name=":28">{{Cite journal|last1=Mitchell|first1=Kieren J.|last2=Bray|first2=Sarah C.|last3=Bover|first3=Pere|last4=Soibelzon|first4=Leopoldo|last5=Schubert|first5=Blaine W.|last6=Prevosti|first6=Francisco|last7=Prieto|first7=Alfredo|last8=Martin|first8=Fabiana|last9=Austin|first9=Jeremy J.|last10=Cooper|first10=Alan|date=2016-04-30|title=Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America|journal=Biology Letters|volume=12|issue=4|pages=20160062|doi=10.1098/rsbl.2016.0062|pmc=4881349|pmid=27095265}}</ref><ref name=":132"/><ref name="Meloro 133–146">{{Cite journal|last1=Meloro|first1=Carlo|last2=de Oliveira|first2=Alessandro Marques|date=2019-03-01|title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |journal=Journal of Mammalian Evolution |volume=26|issue=1|pages=133–146|doi=10.1007/s10914-017-9413-x|s2cid=25839635 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf}}</ref> A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" /> The [[paw]]s ([[metapodial]]s and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''' paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the first digit ([[Toe|hallux]]) of ''Arctodus'' was positioned more closely and parallel to the other four digits (i.e. with straight toes, ''Arctodus'' had less lateral splaying).<ref name=":272">{{Cite thesis |title=Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia |url=https://scholarworks.alaska.edu/handle/11122/9491 |date=1997 |degree=PhD |language=en |first=Paul Edward |last=Matheus}}</ref> This theory is potentially contradicted by trackways tentatively attributed to ''Arctodus'' from near [[Lakeview, Oregon|Lakeview]] in [[Oregon]]. The trackways, which fit the dimensions of ''Arctodus simus''<nowiki/>' paws, exhibit extreme toe splaying, with three centrally aligned, evenly spaced toes at the front, and two almost perpendicular toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had an oval-shaped, undivided pad on its sole (with no toe pad impressions), with front paws that were slightly larger than its back paws, possessed long claws, and had its hind foot overstep the forefoot when walking, like modern bears.<ref>{{Cite web |last1=Packard |first1=E.L. |last2=Allison |first2=I.S. |last3=Cressman |first3=L.S. |title=Mammalian Tracks in the Late Pliocene or Early Pleistocene Beds of Lake County Oregon |url=https://www.oregongeology.org/milo/archive/MiningDistricts/LakeCounty/UnclassifiedDistrict/LakeCountyFossilLocalities/LakeCountyFossilLocalitiesReports.pdf |access-date=June 11, 2017 |website=Oregon Geology}}</ref> For comparison, the [[Manus (anatomy)|manus]] of the spectacled bear has five digits arrayed in a shallow arc, and claws which are quite long, and which also extend far in front of their respective digits.<ref>{{Cite journal |last=Weems |first=Robert E. |date=2018 |title=An Early Pleistocene (Early Irvingtonian) Footprint Fauna from the Bacons Castle Formation, Westmoreland Formation, Virginia |url=https://www.researchgate.net/publication/348579743 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=79 |pages=731–748 |via=ResearchGate}}</ref> Some claw marks attributed to ''Arctodus simus'' at [[Riverbluff Cave]] (as they were four meters above the floor of the cave) were nearly 20&nbsp;cm in width.<ref name=":1">{{Cite journal |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |title=Cenozoic Vertebrate Tracks and Traces |last2=Spielmann |first2=Justin A. |last3=Lockley |first3=Martin G. |date=2007 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=42 |language=en}}</ref> The presence of a partial [[Sesamoid bone#Other animals|false thumb]] in ''Arctodus simus'' is a characteristic shared with ''[[Tremarctos floridanus]]'' and the [[spectacled bear]], and is possibly an [[Plesiomorphy and symplesiomorphy|ancestral]] trait. Absent in [[Ursinae|ursines]], the false thumb of the spectacled bear has been suggested to assist in herbivorous food manipulation (such as extracting [[Mast (botany)|mast]], e.g. [[Bromeliaceae|bromelaid]]/[[Heart of palm|palm hearts]]), or [[arboreality]].<ref>{{Cite journal |last1=Salesa |first1=M. J. |last2=Siliceo |first2=G. |last3=Antón |first3=M. |last4=Abella |first4=J. |last5=Montoya |first5=P. |last6=Morales |first6=J. |date=2006-12-30 |title=Anatomy of the "false thumb" of Tremarctos ornatus (Carnivora, Ursidae, Tremarctinae): Phylogenetic and functional implications |url=http://estudiosgeol.revistas.csic.es/index.php/estudiosgeol/article/view/33/32 |journal=Estudios Geológicos |volume=62 |issue=1 |pages=389–394 |doi=10.3989/egeol.0662133 |issn=1988-3250}}</ref> ==== Maturity ==== Examinations on a young individual of ''Arctodus simus'' from an [[Ozarks|Ozark]] cave suggest that ''Arctodus'', like other [[Bear|ursids]], reached [[sexual maturity]] before [[Bone age|osteological maturity]]. Comparisons with known [[Epiphyseal plate|epiphyseal fusion sequences]] in [[American black bear|''Ursus americanus'']] demonstrated that while the individual was not osteologically mature when it died (numerous [[Epiphysis|epiphyses]] were unfused) the stage of fusion of the [[long bone]] [[epiphyseal plate]]s indicated that the specimen was mostly full sized, and was therefore sexually mature well before such fusions are complete. If ''Arctodus'' were similar in their timing of sexual maturity to modern ''Ursus americanus'', then the ''Arctodus'' specimen was already sexually mature, and was either 4–6 years of age if female, or 6–8 years if the specimen was male. Additionally, wear patterns on the individual's teeth are similar to a 4-6 year old ''Ursus americanus''. For comparison, female [[Spectacled bear|''Tremarctos ornatus'']] reach sexual maturity ~4 years of age, female [[American black bear|''Ursus americanus'']] become sexually mature between 2–4 years of age, and female [[Brown bear|''Ursus arctos'']] begin breeding in some portions of their range at around 3 years.<ref name=":2" /> Fused [[Sutures of skull|sutures]] and [[tooth eruption]] have been used to determine adulthood in ''Arctodus''.<ref name="Pedersen 2728–2736.e8" /> ==Paleobiology== [[File:South Florida Museum - Big Carnivore Skeleton.jpg|thumb|A reconstruction of ''Arctodus pristinus'', from the [[Bishop Museum of Science and Nature]], Florida.]] === ''Arctodus pristinus'' === ==== Paleoecology ==== Although smaller than its descendant, ''Arctodus pristinus'' was still a relatively large tremarctine bear.<ref name=":262"/> Sometimes referred to as the eastern short-faced bear,<ref>{{Cite book |last=Grumet |first=Robert S. |title=Bay, Plain, and Piedmont- A Landscape History of the Chesapeake Heartland from 1.3 Billion Years Ago to 2000 |publisher=The Chesapeake Bay Heritage Context Project |date=September 2000 |pages=16, 21, 167}}</ref> ''Arctodus pristinus'' has been found in [[Kansas]], [[South Carolina]], [[Maryland]] and [[Pennsylvania]] in the [[United States|US]], and [[Aguascalientes]] in [[Mexico]].<ref name=":53">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |s2cid=168164209}}</ref><ref name=":822">{{Cite book |last=Sanders |first=Albert E. |url=https://books.google.com/books?id=LS8LAAAAIAAJ&dq=pristinus+south+carolina&pg=PA48 |title=Additions to the Pleistocene Mammal Faunas of South Carolina, North Carolina, and Georgia |date=2002 |publisher=American Philosophical Society |isbn=978-0-87169-925-1}}</ref> In the Early Pleistocene, ''Arctodus pristinus'' was much more populous the south-east of North America, whereas the black bear was more common in the north-east.<ref>{{Cite book |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=ZFfPDwAAQBAJ&dq=Cumberland+Bone+Cave+arctodus&pg=PA740 |title=Fossil Record 6 Volume 2 |last2=Sullivan |first2=Robert M. |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref> ''Arctodus pristinus'' is particularly well known from Florida, especially from the Leisley Shell Pit.<ref>{{Cite journal |last=Berta |first=Annalisa |date=1995 |title=Fossil carnivores from the Leisley Shell Pit, Hillsborough County, Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-14.pdf |journal=Florida Museum of Natural History |volume=37 Part II |issue=14 |pages=436–499}}</ref> ''Arctodus pristinus'' is considered a biochronological indicator for the period between the Late Blancan and late Irvingtonian periods of Pleistocene Florida.<ref name=":5" /> ==== Hibernation ==== ''Arctodus pristinus'' specimens have been found in caves such as [[Port Kennedy Bone Cave|Port Kennedy]], Pennsylvania (where fossils from as many as 36 individuals have been found), and [[Cumberland Bone Cave|Cumberland Cave]], Maryland, often in association with the black bear. This suggests a close association with the biome.<ref name=":5" /><ref name="researchgate.net"/> === ''Arctodus simus'' === ==== Paleoecology ==== [[File:Camino_a_paso_de_Cortès._-_panoramio.jpg|thumb|238x238px|[[Woodland|Open woodlands]], such as those in the [[Trans-Mexican Volcanic Belt|Mexican highlands]], would have presented ample foraging opportunities for ''Arctodus''.|left]] Evolving from the smaller ''A. pristinus'' around 1.1 million years ago, scholars today mostly conclude that ''Arctodus simus'' was a colossal, opportunistic [[omnivore]], with a flexible, locally adapted diet akin to the [[brown bear]].<ref name="Figueiridio_et_al_20102"/><ref>{{Cite book |last=Nowak, Ronald M. |title=Walker's mammals of the world |date=1999 |publisher=Johns Hopkins University Press |isbn=0-8018-5789-9 |edition=Sixth |location=Baltimore |oclc=39045218}}</ref><ref name=":302"/><ref name=":156">{{Cite journal |last1=Steffen |first1=Martina L. |last2=Fulton |first2=Tara L. |date=2018-02-01 |title=On the association of giant short-faced bear (Arctodus simus) and brown bear (Ursus arctos) in late Pleistocene North America |journal=Geobios |volume=51 |issue=1 |pages=61–74 |doi=10.1016/j.geobios.2017.12.001}}</ref> If ''Arctodus simus'' wasn't largely herbivorous,<ref name=":53" /><ref name=":132"/> the scavenging of [[megaherbivore]] carcasses, and the occasional predatory kill would have complimented the large amounts of vegetation consumed when available.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/> [[Carbon-13]] ([[Δ13C|''δ''<sup>13</sup>C]]) isotope data gathered from ''Arctodus'' specimens from [[Beringia]], [[California]] and [[Mexico]], indicates that ''Arctodus simus'' had a diet based on [[C3 carbon fixation|C3 resources]]. Preferring closed habitat ([[Woodland|open woodland]] & [[forest]]), ''Arctodus'' consumed [[C3 carbon fixation|C3 vegetation]] ([[Leaf|leaves]], [[Plant stem|stems]], [[fruit]]s, [[Bark (botany)|bark]], and [[flower]]s from trees, shrubs, and cool season [[Poaceae|grasses]]) and the browsers that fed on them, such as [[deer]], [[Camelidae|camelids]], [[Tapirus|tapir]], [[bison]] and [[ground sloth]]s.<ref name="Figueiridio_et_al_20102"/><ref name=":232">{{Cite journal |last1=Trayler |first1=Robin B. |last2=Dundas |first2=Robert G. |last3=Fox-Dobbs |first3=Kena |last4=Van De Water |first4=Peter K. |date=2015-11-01 |title=Inland California during the Pleistocene—Megafaunal stable isotope records reveal new paleoecological and paleoenvironmental insights |url=https://www.sciencedirect.com/science/article/pii/S0031018215004010 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=437 |pages=132–140 |doi=10.1016/j.palaeo.2015.07.034 |bibcode=2015PPP...437..132T |issn=0031-0182}}</ref> Occasionally referred to as the great short-faced bear, ''Arctodus simus'' was particularly plentiful in western [[North America]]. ''Arctodus simus'' was integral to what has been referred to as the ''[[Camelops]]'' fauna, or alternatively ''Camelops''/''[[American mountain deer|Odocoileus lucasi]]'' ("''Navahoceros''") fauna, a faunal province centered in Western North America. The ''Camelops'' fauna was also characterized by [[Euceratherium|shrub-ox]], [[prairie dog]]s, [[Capromeryx|dwarf pronghorns]], [[Nothrotheriops|Shasta ground sloths]], and [[American lion]]s'','' although individual species ranges could shift independently of one another. The diverse flora of the ''Camelops'' faunal province included montane conifers and oak park lands, shrub and grassland that stretched across the [[North American Cordillera]] south of Canada, to the [[Valley of Mexico]]. This supported a variety of large grazing and browsing mammals such as mammoth, horses, bison, mastodon, deer, pronghorns and large ground sloths.<ref>{{Cite journal |last=Pichardo |first=Mario |date=2003 |title=Overview of Central Mexican Prehistory: Morphostratigraphy, Chronostratigraphy, Biostratigraphy |url=https://www.jstor.org/stable/29542453 |journal=Anthropologischer Anzeiger |volume=61 |issue=2 |pages=141–174 |doi=10.1127/anthranz/61/2003/141 |jstor=29542453 |pmid=12872543 |issn=0003-5548}}</ref><ref>{{Cite web |title=KGS--Guidebook 5--Wisconsinan Mammalian Faunas |url=https://www.kgs.ku.edu/Publications/Bulletins/GB5/Martin2/ |access-date=2022-08-01 |website=www.kgs.ku.edu}}</ref><ref name=":9">{{Cite journal |last1=Martin |first1=Larry |last2=Neuner |first2=A. |date=1978-01-01 |title=The End of the Pleistocene in North America |url=https://digitalcommons.unl.edu/tnas/337 |journal=Transactions of the Nebraska Academy of Sciences and Affiliated Societies}}</ref> As ''Arctodus'' has been recovered from a comparatively small number of finds in relation to other large carnivorans, ''Arctodus'' is suggested to have lived in low population densities.<ref name="Pedersen 2728–2736.e82">{{Cite journal |last1=Pedersen |first1=Mikkel Winther |last2=De Sanctis |first2=Bianca |last3=Saremi |first3=Nedda F. |last4=Sikora |first4=Martin |last5=Puckett |first5=Emily E. |last6=Gu |first6=Zhenquan |last7=Moon |first7=Katherine L. |last8=Kapp |first8=Joshua D. |last9=Vinner |first9=Lasse |last10=Vardanyan |first10=Zaruhi |last11=Ardelean |first11=Ciprian F. |date=2021-06-21 |title=Environmental genomics of Late Pleistocene black bears and giant short-faced bears |journal=Current Biology |volume=31 |issue=12 |pages=2728–2736.e8 |doi=10.1016/j.cub.2021.04.027 |pmid=33878301 |hdl-access=free |s2cid=233303447 |hdl=10037/22808}}</ref> Typically thought of as an open habitat specialist, ''Arctodus'' seems to have also been abundant in mixed habitat where [[C3 carbon fixation|C3 vegetation]] was available. Based on the wide distribution of the species, ''Arctodus simus'' inhabited diverse climatic conditions and all sorts of environments, ranging from [[Taiga|boreal forests]] and [[mammoth steppe]] in the north, [[Grassland|open plains]] and [[Montane ecosystems|highland woodlands]] in the interior, [[Subtropics|subtropical]] [[woodland]]s and [[savanna]]s in the south, to the [[Trans-Mexican Volcanic Belt pine–oak forests|pine–oak forests]] of the [[Trans-Mexican Volcanic Belt]], the boundary of the [[Nearctic realm]].<ref name=":352"/><ref name=":02"/><ref name=":102">{{Cite journal |last1=Russell |first1=Dale A. |last2=Rich |first2=Fredrick J. |last3=Schneider |first3=Vincent |last4=Lynch-Stieglitz |first4=Jean |date=May 2009 |title=A warm thermal enclave in the Late Pleistocene of the South-eastern United States |journal=Biological Reviews |volume=84 |issue=2 |pages=173–202 |doi=10.1111/j.1469-185X.2008.00069.x |pmid=19391200 |s2cid=9609391}}</ref><ref name=":132" /><ref name=":410">{{Cite journal |last1=Pérez-Crespo |first1=Víctor Adrián |last2=Arroyo-Cabrales |first2=Joaquín |last3=Morales-Puente |first3=Pedro |last4=Cienfuegos-Alvarado |first4=Edith |last5=Otero |first5=Francisco J. |date=March 2018 |title=Diet and habitat of mesomammals and megamammals from Cedral, San Luis Potosí, México |journal=Geological Magazine |volume=155 |issue=3 |pages=674–684 |bibcode=2018GeoM..155..674P |doi=10.1017/S0016756816000935 |s2cid=132502543}}</ref><ref name=":373">{{Cite journal |last=Eng-Ponce |first=Joaquin |date=August 2021 |title=Reconstruccion paeloambiental del yacimiento La Cinta-Portalitos, Michoacan-Guanajuato, Mexico (thesis) |url=http://bibliotecavirtual.dgb.umich.mx:8083/xmlui/bitstream/handle/DGB_UMICH/6432/FB-M-2021-0909.pdf |journal=Faculty of Biology, Universidad Michoacana de San Nicolás de Hidalgo}}</ref> Preliminary data suggests that certain habitat was optimal for ''Arctodus simus'' populations- the [[pluvial lake]]s, [[Pinyon–juniper woodland|montane forests]] and [[Shrub–steppe|arid sagebrush steppe/grassy plains]] of the inland western USA,<ref>{{Cite journal |last=Grayson |first=Donald K. |date=2006-11-01 |title=The Late Quaternary biogeographic histories of some Great Basin mammals (western USA) |url=https://www.sciencedirect.com/science/article/pii/S0277379106001405 |journal=Quaternary Science Reviews |language=en |volume=25 |issue=21 |pages=2964–2991 |doi=10.1016/j.quascirev.2006.03.004 |bibcode=2006QSRv...25.2964G |issn=0277-3791}}</ref> the [[Montane ecosystems|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], [[Paludification|paludified]] [[mammoth steppe]] in [[Beringia]], and the [[Savanna|mixed savannas]] of the [[Basin and Range Province|south-western USA]] and [[Mexican Plateau]].<ref name=":92" /><ref name=":19" /><ref name=":142">{{Cite journal |last1=Figueirido |first1=Borja |last2=Perez |first2=Alejandro |last3=Schubert |first3=Blaine |last4=Serrano |first4=Francisco |last5=Farrell |first5=Aisling |last6=Pastor |first6=Francisco |last7=Neves |first7=Aline |last8=Romero |first8=Alejandro |date=2017-12-19 |title=Dental caries in the fossil record: A window to the evolution of dietary plasticity in an extinct bear |url=https://www.researchgate.net/publication/321791811 |journal=Scientific Reports |volume=7 |issue=1 |page=17813 |bibcode=2017NatSR...717813F |doi=10.1038/s41598-017-18116-0 |pmc=5736623 |pmid=29259277}}</ref> ==== Competition with ursine bears ==== [[File:Arctodus Simus, Hot Springs, South Dakota.jpg|thumb|''Arctodus simus'' reconstruction at the [[The Mammoth Site|Hot Springs Mammoth Site]], South Dakota.]] Black bears inhabited North America since at least the [[Chibanian|Middle Pleistocene]], whereas [[brown bear]]s, along with [[American lion|lions]], [[bison]] and [[red fox]]es, first emigrated to [[North America]] via [[Beringia]] during the [[Illinoian (stage)|Illinoian Glaciation]] (~170,000 BP).<ref name=":19" /><ref name=":14" /> ''Arctodus simus'' may have been out-competed by [[brown bear]]s as the latter expanded southwards from eastern [[Beringia]], and gradually established itself in [[North America]]. Brown bears and ''Arctodus'' have been reported together in Alaska before ∼34,000 BP, and in later Pleistocene deposits in [[Vancouver Island]], [[Wyoming]] and [[Nevada]]. Although a 2018 study hypothesized that both species did not overlap territorially on Vancouver Island,<ref name=":156"/> a revision of radiocarbon dates by a 2022 study concluded that brown bears, black bears and ''Arctodus simus'' all co-existed on Vancouver Island once the island de-glaciated ~14,500 BP. Noting that all three bears relied on terrestrial resources, the black bears occupied a distinctly lower trophic position in relation to the brown bear, with ''Arctodus'' holding an intermediate position according to a compound‐specific stable isotope analysis. However, this may be an underestimate- an analysis [[Δ15N|''δ''<sup>15</sup>N]] [[threonine]] suggests that protein consumption may be higher in ''Arctodus'' than the other bear species. This may indicate a differentiation in prey choice within the same trophic level (e.g. insects versus terrestrial, plant‐consuming mammals).<ref name=":14" /> The base differences of ''[[Δ13C|δ]]''<sup>[[Δ13C|13]]</sup>[[Δ13C|C]] and [[Δ15N|''δ''<sup>15</sup>N]] values between brown and black bears was narrow, which could be due to the lack of consumption of aquatic resources by the higher trophic level taxa. Although these samples show potential range overlap between species, it is possible that the different taxa were specialized to different environmental settings, which vary greatly across small geographical areas on the mountainous island. The standard differentiation between the more open adapted brown bear and closed forest-adapted black bear is complicated by competition from ''Arctodus simus,'' which seems to have preferred more open habitat.<ref name=":14" /> Additionally, the ''Arctodus'' specimens from Vancouver Island are believed to be female- that modern female brown bears had significant differences in nitrogen-15 values with male brown bears where they co-exist with black bears, and that very large brown bears may not be able to sustain themselves on a vegetarian diet, could indicate size as a constraint on the level of herbivory possible for short‐faced bears. Correspondingly, a sex‐patterned difference in ''δ''<sup>15</sup>N values of bear collagen was observed.<ref name=":14">{{Cite journal |last1=Kubiak |first1=Cara |last2=Grimes |first2=Vaughan |last3=Van Biesen |first3=Geert |last4=Keddie |first4=Grant |last5=Buckley |first5=Mike |last6=Macdonald |first6=Reba |last7=Richards |first7=M. P. |date=2022-06-27 |title=Dietary niche separation of three Late Pleistocene bear species from Vancouver Island, on the Pacific Northwest Coast of North America |url=https://onlinelibrary.wiley.com/doi/10.1002/jqs.3451 |journal=Journal of Quaternary Science |language=en |pages=jqs.3451 |doi=10.1002/jqs.3451 |s2cid=250134103 |issn=0267-8179}}</ref> Meat consumption is confirmed by elevated isotope (''[[Δ13C|δ]]''<sup>[[Δ13C|13]]</sup>[[Δ13C|C]] and [[Δ15N|''δ''<sup>15</sup>N]]) values in numerous [[Beringia]]n [[late Pleistocene]] ''Arctodus simus'' specimens where these bears may have competed for food, but usually occupied a higher [[trophic level]] compared with invading brown bears. For example, inland [[Beringia]]n [[brown bear]]s from the late Pleistocene (exception being to specimens from the [[Yukon]]) consumed [[Embryophyte|terrestrial vegetation]] and [[salmon]] at similar proportions to modern coastal populations, whereas modern inland populations of northern brown bears showed no signatures associated with significant [[salmon]] consumption. In both inland populations of Late Pleistocene Beringian brown bears, reduced signatures of terrestrial meat consumption were noted. On the other hand, data from Beringian specimens of ''Arctodus'' suggest that while omnivorous, only terrestrial sources of meat were important for northern ''Arctodus''.<ref name=":402" /> This contrast is represented in the data- isotopic data from Beringian ''Arctodus'' clusters tightly, and groups differently to Beringian brown bears, although there is overlap.<ref name=":402" /> The forcing of a smaller bear into a more herbivorous diet has been compared to the modern relationship between brown bears and [[American black bear]]s,<ref name=":272" /><ref name=":312">{{Cite journal |last=Bocherens |first=Hervé |date=2015-06-01 |title=Isotopic tracking of large carnivore palaeoecology in the mammoth steppe |url=https://www.sciencedirect.com/science/article/pii/S0277379115001250 |journal=Quaternary Science Reviews |language=en |volume=117 |pages=42–71 |doi=10.1016/j.quascirev.2015.03.018 |bibcode=2015QSRv..117...42B |issn=0277-3791}}</ref> with the black bears often consuming large amounts of salmon and other higher trophic‐level resources in environments where brown bears are rare or absent. Where they overlap, brown bears are observed to take over the higher trophic niche, create avoidance at the population level and seasonally displacing local black bears. Ultimately, black bears tend to have much lower population densities in areas where brown bears are also present. In locations where these two species coexist today, black bears' territorial ranges are much smaller than the ranges of sympatric brown bears.<ref name=":14" /> [[File:Ursus_americanus_PO_04.jpg|thumb|Black bears were much larger in the Pleistocene, and have been found in association with ''Arctodus'' across North America.]] That ''Arctodus simus'' (along with the expansion of [[Mire|peatlands]]) may have excluded brown bears from Eastern Beringia from ∼34,000 to ∼23,000 BP further suggests that ''Arctodus'' may typically have been dominant over brown bears.<ref name=":422">{{Cite journal |last1=Murchie |first1=Tyler J. |last2=Monteath |first2=Alistair J. |last3=Mahony |first3=Matthew E. |last4=Long |first4=George S. |last5=Cocker |first5=Scott |last6=Sadoway |first6=Tara |last7=Karpinski |first7=Emil |last8=Zazula |first8=Grant |last9=MacPhee |first9=Ross D. E. |last10=Froese |first10=Duane |last11=Poinar |first11=Hendrik N. |date=2021-12-08 |title=Collapse of the mammoth-steppe in central Yukon as revealed by ancient environmental DNA |journal=Nature Communications |language=en |volume=12 |issue=1 |pages=7120 |doi=10.1038/s41467-021-27439-6 |pmid=34880234 |pmc=8654998 |bibcode=2021NatCo..12.7120M |issn=2041-1723}}</ref><ref name=":432">{{Cite journal |last1=Barnes |first1=I. |last2=Matheus |first2=P. |last3=Shapiro |first3=B. |last4=Jensen |first4=D. |last5=Cooper |first5=A. |date=2002-03-22 |title=Dynamics of Pleistocene Population Extinctions in Beringian Brown Bears |url=https://www.science.org/doi/10.1126/science.1067814 |journal=Science |language=en |volume=295 |issue=5563 |pages=2267–2270 |doi=10.1126/science.1067814 |pmid=11910112 |bibcode=2002Sci...295.2267B |s2cid=5883943 |issn=0036-8075}}</ref> When ''Arctodus'' went extinct in Beringia ~23,000 BP, [[brown bear]]s recolonised [[Beringia]], but had more carnivorous diets than their [[Beringia]]n kin pre ~34,000 BP. This bolsters the idea that these bears competed for similar resources and niches.<ref name=":19" /><ref name=":156" /> Similarly, while more herbivorous in Beringia while competing with ''Arctodus'', brown bears seem to have been more carnivorous when co-existing with cave bears in [[Eurasia]] (''[[Cave bear|Ursus spelaeus]]'').<ref name=":312" /> Extinction and repopulation is further evidenced by the high genetic (mitochondrial) diversity of Beringian brown bears between 59,000 BP and 10,000 BP (16 haplotypes from 27 samples) in contrast with Beringian ''Arctodus simus'' (7 haplotypes from 23 samples). This contrast in genetic diversity has also been hypothesized to suggest that while brown bears are female [[Philopatry|philopatric]] (i.e. females have a permanent home range), ''Arctodus simus'' may not have been, at least not to the same extent.<ref name=":492">{{Cite journal |last=Bray |first=Sarah C. E. |date=September 2010 |title=Mitochondrial DNA Analysis of the Evolution and Genetic Diversity of Ancient and Extinct Bears |url=https://digital.library.adelaide.edu.au/dspace/bitstream/2440/66285/8/02whole.pdf |journal=School of Environmental and Earth Sciences, University of Adelaide (PHD) |pages=214 (230)}}</ref> On a continent-wide scale, the 2018 study explained that although brown and ''Arctodus simus'' were [[Sympatry|sympatric]] at times as brown bears spread through North America, ''Arctodus simus'' may typically have dominated [[Competition (biology)|competitive]] interactions, particularly when their populations were robust, and displaced brown bears from specific localities. At the end of the Pleistocene one reason [[brown bear]]s persisted where ''Arctodus simus'' went extinct was because ''Arctodus'' may have been less flexible in adapting to new and rapidly changing environments that impacted the availability or quality of food and possibly habitat.<ref name=":156" /> ==== Hibernation ==== [[File:Fall_in_the_Ozarks.jpg|thumb|231x231px|Although [[North America|pan-continental]], ''Arctodus'' specimens have been particularly plentiful from [[Karst|caves]] in the [[Montane ecosystems|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], such as the [[Ozarks]].|left]] According to a 2003 study, in [[Karst|karst regions]], fossils of ''Arctodus simus'' have been recovered almost exclusively from cave sites. In the contiguous United States, 26 of 69 ''Arctodus simus'' sites (~38%) are in caves. That greater than one-third of all sites are caves suggests a close association between this species and cave environments. Furthermore, over 70% of the smaller specimens (once assigned as the ''A. s. simus'' subspecies) are from cave deposits. Not one of the specimens assigned to the larger morph (''A. s. yukonensis'') is from a cave passage. Taking into account the fact that female [[Bear|ursids]] are smaller and more prone to den in caves, it seems logical to conclude that the majority of ''Arctodus simus'' from such deposits were females and may have been denning when they perished.<ref name=":210">{{Cite journal |last1=CHUBERT |first1=BLAINE |last2=KAUFMANN |first2=JAMES |date=2003-08-01 |title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species |url=https://www.researchgate.net/publication/252748398 |journal=Journal of Cave and Karst Studies |volume=65}}</ref> In the [[Americas]], the [[spectacled bear]], [[brown bear]], and [[American black bear|black bear]] use caves for denning when available, and polar bears dig their own "caves" in snow.<ref name=":210" /> Female [[American black bear|black bears]] and [[brown bear]]s in cooler climates enter dens earlier and stay for longer than males. Female [[American black bear|black bears]] and [[brown bear]]s in warmer portions of their range, along with pregnant female [[polar bear]]s, usually den, and often go into [[dormancy]], [[torpor]] and/or maternal denning in winter, while males stay active all year.<ref name=":122">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |bibcode=2010QuInt.217..188S |doi=10.1016/j.quaint.2009.11.010}}</ref> Female specimens of ''Arctodus simus'' have been inferred to have been exhibiting maternal denning, however the expression of metabolic denning ([[hibernation]]/torpor) is unclear in ''Arctodus.''<ref name=":310">{{Cite journal |last1=Fowler |first1=Nicholas L. |last2=Spady |first2=Thomas J. |last3=Wang |first3=Guiming |last4=Leopold |first4=Bruce D. |last5=Belant |first5=Jerrold L. |date=October 2021 |title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51 |issue=4 |pages=465–481 |doi=10.1111/mam.12246 |s2cid=233847639}}</ref> Moreover, to date, there are no records of adults with associated offspring from caves.<ref name=":122" /> However, ''[[Arctotherium|Arctotherium angustidens]]'', a fellow [[Tremarctinae|giant short-faced bear]], has recovered from a cave in [[Argentina]] with offspring.<ref>{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Pomi |first2=Lucas H. |last3=Tonni |first3=Eduardo P. |last4=Rodriguez |first4=Sergio |last5=Dondas |first5=Alejandro |date=2009-09-01 |title=First report of a South American short-faced bears' den (Arctotherium angustidens): palaeobiological and palaeoecological implications |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=33 |issue=3 |pages=211–222 |doi=10.1080/03115510902844418 |issn=0311-5518 |s2cid=55636895|url=http://sedici.unlp.edu.ar/handle/10915/5364 }}</ref> Numerous "bear" beds often preserve ''Arctodus simus'' and both Pleistocene and modern [[American black bear]]s in association (''U.a. amplidens'' and ''U. a. americanus'')- such deposits have been found in [[Missouri]], [[Oklahoma]] and Potter Creek Cave, California, where 8 individuals of ''A. simus'' have been found. These mixed deposits are assumed to have accumulated over time as individual bears (including ''Arctodus'') died during winter sleep.<ref>{{Cite journal |last1=Czaplewski |first1=Nicholas |last2=Rogers |first2=Kyler |last3=Russell |first3=Clayton |date=2018-06-01 |title=Late pleistocene vertebrates from three-forks cave, Adair county, Oklahoma Ozark highland |url=https://www.researchgate.net/publication/324068143 |journal=Journal of Cave and Karst Studies |volume=80 |issue=2 |pages=1–16 |doi=10.4311/2017PA0118 |doi-access=free}}</ref><ref>{{Cite journal |last=Puckette |first=William L. |date=1976 |title=Notes on the occurrence of the short-faced bear (Arctodus) in Oklahoma |url=https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.605.3584&rep=rep1&type=pdf |journal=Proceedings of the Oklahoma Academy of Science |volume=56 |pages=67–68|citeseerx=10.1.1.605.3584 }}</ref><ref>{{Cite journal |last=Feranec |first=Robert S |date=2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |url=https://www.cambridge.org/core/product/identifier/S0033822200034007/type/journal_article |journal=Radiocarbon |language=en |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |issn=0033-8222}}</ref> Furthermore, [[environmental DNA]] suggests that ''Arctodus'' and black bears shared a cave in [[Chiquihuite cave]] in [[Zacatecas]].<ref name="Pedersen 2728–2736.e82" /> At the [[Schell Creek Range|Labor-of-Love cave]] in [[Nevada]], both American black bears and [[brown bear]]s have been found in association with ''Arctodus simus''. A study in 1985 noted that [[sympatry]] between ''Arctodus'' and brown bears preserved in caves is rare, with only [[Converse County, Wyoming|Little Box Elder Cave]] in [[Wyoming]] and Fairbanks II site in [[Alaska]] hosting similar remains.<ref name=":132"/><ref name=":362"/> ==== Paleopathology ==== Beyond dietary dental pathologies present in the genus, the most nearly complete skeleton of ''Arctodus'' preserves extensive pathologies on the skeleton. One hypothesis suggests the [[Fulton County, Indiana|Fulton County]] ''Arctodus'' specimen suffered from a [[syphilis]]-like ([[Treponemal diseases|trepanemal]]) disease, or [[yaws]], based on [[lesion]]s on the [[vertebra]]e, [[ribs]] and both [[ulna]]e.<ref name=":392">{{Cite book |last1=Richards |first1=Ronald L. |url=https://www.biodiversitylibrary.org/bibliography/3480 |title=Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, northern Indiana |last2=Neiburger |first2=Ellis J. |last3=Turnbull |first3=William D. |date=1995 |publisher=Field Museum of Natural History |location=Chicago, Ill.}}</ref><ref>{{Cite book |last1=Rothschild |first1=Bruce M. |url=https://books.google.com/books?id=AGfmCQAAQBAJ&dq=%22arctodus%22+treponemal+infection+rothschild&pg=PA105 |title=Skeletal Impact of Disease: Bulletin 33 |last2=Martin |first2=Larry D. |date=2006 |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref><ref>{{Cite journal |last=Rothschild |first=Bruce M. |date=13 October 1988 |title=Scientific Correspondence |url=https://www.nature.com/articles/335595a0.pdf?origin=ppub |journal=Nature |volume=335 |issue=Existence of syphilis in a Pleistocene bear |pages=595 |doi=10.1038/335595a0 |pmid=3050529 |s2cid=4280184}}</ref> However, alternate hypotheses include [[tuberculosis]], [[osteomyelitis]], [[arthritis]] or a [[fungal infection]], either singularly or in combination with other causes. The same individual records a pathological growth distorting the [[Deltoid muscle|deltoid]] and [[Pectoral muscles|pectoral]] ridges on the right [[humerus]].<ref name=":110"/> Furthermore, [[Dental abscess|abscesses]] are noted between the m1 and m2 of both [[dentaries]], and on [[Abscess|both ulna]]. Hypotheses include syphilis, [[osteoarthritis]], a fungal infection in addition to long term syphilis, or an infected wound.<ref name=":392" /><ref>{{Cite journal |last1=Pinto |first1=A. C. |last2=Etxebarría |first2=F. |date=2001 |title=Description of pathological conditions in the skeleton of an adult male brown bear Ursus arctos from the Cantabrian range of mountains (Reserva Nacional de Caza de Riaño, León) Coruña |url=https://www.udc.es/files/iux/almacen/articulos/cd26_art33.pdf |journal=Cadernos Lab. Xeolóxico de Laxe |volume=2001 |pages=471 |issn=0213-4497}}</ref> == Distribution & habitat == === Map === {{location map+|North America|relief=yes|width=700|float=left|caption=Distribution map of ''Arctodus''<br /> Legend: [[File:Red_pog.svg|8px]] Late Pleistocene ''A. simus'' [[File:Purple 8000ff pog.svg|8px]] Radiocarbon dated ''A.simus'' (<50,000 BP) [[File:Blue_pog.svg|8px]] Early/Middle Pleistocene ([[Irvingtonian]]) ''A.simus'' [[File:Cyan_pog.svg|8px]] ''A. pristinus''|places={{location map~ | North America 2 | label = Friesenhahn Cave | position = none | lat=29.682853 | long=-98.477758 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Bonner Springs (Kansas River) | position = none | lat=39.059722 | long=-94.883611 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Huntington Dam | position = none | lat=39.596595 |long=-111.273836 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Fulton County | position = none | lat=41.0619441 |long=-86.206667|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Sheriden Cave | position = none | lat=40.980733 | long=-83.444783| mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Pellucidar Cave | position = none | lat=50.400278 | long=-126.975833| mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Salt Lake Valley (Silver Creek/Bonneville) | position = none | lat=40.6839 | long=-111.978|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = San Miguel Island (Daisy Cave) | position = none | lat=34.033333 |long=-120.383333|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Saltville Valley | position = none | lat=36.873611 |long=-81.760833|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = La Sena | position = none | lat=40.53325 |long=-100.384545| mark= Purple 8000ff pog.svg }} {{location map~ |North America 2 | label = Gold Run Creek | position = none | lat=63.698261 |long=-138.609632 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Ikpikpuk River | position = none | lat=69.683333 |long= -154.900000 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = La Brea Tar Pits | position = none | lat=34.0628 |long=-118.356|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Lower Hunker Creek | position = none | lat=63.971024 |long= -138.985973 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Three-Forks Cave (Gittin' Down Mountain) | position = none | lat=35.76509 |long=-94.74022|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Island Ford Cave | position = none | lat=37.786111 | long=-79.988889| mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Sixtymile River | position = none | lat= 63.554796 | long= -139.825129 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Titaluk River | position = none | lat=69.427684 |long=-156.999745 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Ophir Creek | position = none | lat=63.82 |long=-139.34579 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Hester Creek | position = none | lat=63.97 |long=-139.1 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Canyon Creek | position = none | lat=63.82 |long=-139.1 |mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Birch Creek | position = none | lat= 66.255187 | long= -145.835918 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Chiquihuite Cave | position = none | lat= 24.609470 | long= -101.188001 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Eldorado Creek | position = none | lat= 63.91885 | long= -139.31552 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Quartz Creek | position = none | lat= 63.75224 | long= -139.12377 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Natural Trap Cave | position = none | lat=44.973333 | long= -108.193056 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Cedral | position = none | lat=23.816667 |long=-100.716667|mark= Red_pog.svg}} {{location map~ |North America 2 | label = La Cinta Portalitos | position = none | lat=20.085833 |long=-101.158611|mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lubbock Lake| position = none | lat=33.621944 | long= -101.889722 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Fern Cave| position = none | lat=34.648933 | long= -86.297864 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cooper River| position = none | lat=33.078822 | long= -79.925568 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cedar Creek (Black Belt, c.f.) | position = none | lat=33.341435 | long= -88.437362 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = The Bar (Central Mississippi Alluvial Valley) | position = none | lat=33.712994 | long= -91.183510 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Clover Bar (Edmonton) | position = none | lat=53.596164 | long= -113.354075 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lebret | position = none | lat=50.757128| long= -103.702833 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = The Mammoth Site | position = none | lat=43.42471 | long= -103.48313 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Frankstown Cave | position = none | lat= 40.450969 | long= -78.337221 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Samwel Cave | position = none | lat= 40.920055 | long= -122.238879 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Potter Creek Cave | position = none | lat= 40.783624 | long= -122.279719 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Alameda Tube | position = none | lat= 37.792099 | long= -122.275258 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Diamond Valley | position = none | lat= 33.678333 | long= -117.041667 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Camp Cady | position = none | lat= 34.941383 | long= -116.609557 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Maricopa Tar Seeps | position = none | lat= 35.061276 | long= -119.392818 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Drews Gap (Lakeview) | position = none | lat= 42.19927 | long= -120.615498 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Fossil Lake | position = none | lat= 43.3258 | long= -120.4909 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Airport Lane | position = none | lat= 45.294329 | long= -118.021097 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Labor-of-Love Cave | position = none | lat= 39.3667 | long= -114.6 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Little Box Elder Cave | position = none | lat= 42.7833 | long= -105.683 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Riverbluff Cave | position = none | lat= 37.106298 | long= -93.32927 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Tequixquiac | position = none | lat= 19.898093 | long= -99.161302 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cueva Quebrada | position = none | lat= 29.711764 | long= -101.387611 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Jinglebob | position = none | lat= 37.2 | long= -100.3 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Bat Cave | position = none | lat= 37.944433 | long= -92.376168 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cowichan Head | position = none | lat= 48.555260 | long= -123.363879 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Moore Pit (Hill Shuler/ Trinity River) | position = none | lat= 32.711180 | long= -96.706766 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Seale Pit (Hill-Shuler/Trinity River) | position = none | lat= 32.773207 | long= -97.010381 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Carroll Cave | position = none | lat= 37.952488 | long= -92.559982 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Keams Canyon | position = none | lat= 35.813586 | long= -110.204220 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Conkling Cavern | position = none | lat= 32.19 | long= -106.585278 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Burnet Cave | position = none | lat= 32.3667 | long= -104.7833 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = U-Bar Cave | position = none | lat= 31.5667 | long= -108.4 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Isleta Caves | position = none | lat= 34.8833 | long= -106.883 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Blacktail Cave | position = none | lat= 47.106583 | long= -112.274182 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Valsequillo | position = none | lat= 18.925262 | long= -98.146481 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lake San Agustin | position = none | lat= 33.924444 | long= -108.227778 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Big Bear site | position = none | lat= 33.466801 | long= -105.793276 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Albuquerque Gravel Pits | position = none | lat= 35.013227 | long= -106.722222 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Bitter Springs Playa | position = none | lat= 36.676633 | long= -111.713866 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Troublesome Creek | position = none | lat= 41.419528 | long= -95.018005 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = American Falls (Cedar Ridge)| position = none | lat= 42.8 | long= -112.9 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Skeleton Cave | position = none | lat= 43.950267 | long= -121.1773 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Pendejo Cave? | position = none | lat= 32.416667 | long= -105.916667 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Round Spring Cave | position = none | lat= 37.281271 | long= -91.412088 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Powder Mill Creek Cave | position = none | lat= 37.193158 | long= -91.171013 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Ester Creek | position = none | lat= 64.848834 | long= -148.071763 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Engineer Creek | position = none | lat= 64.932586 | long= -147.561827 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Goldstream (Fairbanks) | position = none | lat= 64.929919 | long= -147.641979 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cleary Creek | position = none | lat= 65.106979 | long= -147.473061 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Eva Creek Mine | position = none | lat= 64.85 | long= -147.99999 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lilian Creek | position = none | lat= 65.516989 | long= -148.573169 | mark= Red_pog.svg}} {{location map~ |North America 2 | label = Old Crow Flats | position = none | lat=67.441 |long=-139.82|mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cripple Creek | position = none | lat= 64.761387 | long= -147.307813 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = No.2 G-Strip Area, Alaska | position = none | lat= 64.929919 | long= -147.641979 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Big Bear Cave | position = none | lat= 37.927957 | long= -92.168076 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Schultz Cave | position = none | lat= 30.212894 | long= -99.839868 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Fairmead Landfill| position = none | lat=37.061631 | long= -120.194195 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Murrieta (Riverside)| position = none | lat=33.570661 | long= -117.200222 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Irvington| position = none | lat=37.527222 | long= -121.946111 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Vallecito Creek (Anza-Borrego) | position = none | lat=33.024534 | long= -116.209792 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Hay Springs| position = none | lat=42.7 | long= -102.5 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Rock Creek| position = none | lat=34.54173 | long= -101.42989| mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Arkalon | position = none | lat=37.143012 | long= -100.807423 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Doeden Gravel Pit (Yellowstone River) | position = none | lat= 46.4 | long= -105.8 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Haile 16A | position = none | lat=29.690000 | long= -82.560000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Sebastian Canal 2 | position = none | lat=27.889646 | long= -80.734793 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Port Charlotte | position = none | lat=26.990278 | long= -82.105833 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Crystal River Power Plant (Inglis 1A & Inglis 1B) | position = none | lat=29.010000 | long= -82.690000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Santa Fe River 1 | position = none | lat=29.840000 | long= -82.700000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Apollo Beach, Leisey Shell Pit 1, Leisey Shell Pit 1A & Leisey Shell Pit 3 | position = none | lat=27.690000 | long= -82.500000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = McLeod Limerock Mine | position = none | lat=29.474891 | long= -82.589610 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Kissimmee 6 | position = none | lat=27.385283 | long= -81.083256 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Bass Point Waterway, Rigby Shell Pit, Venice Beach | position = none | lat=27.099834 | long= -82.460045 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Coleman 2A | position = none | lat=28.760000 | long= -82.050000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Port Kennedy Cave | position = none | lat=40.10182 | long= -75.42462 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Cumberland Bone Cave | position = none | lat=39.691389 | long= -78.788472 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Ashley River | position = none | lat=32.847008 | long= -80.050759 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Aguascalientes | position = none | lat=21.976449 | long= -102.283105 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Lost World Caverns | position = none | lat=37.8326 | long= -80.4469 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Stout's Ranch (Saw Rock Canyon) | position = none | lat= 37.1 | long= -100.9 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Lake Chapala? | position = none | lat= 20.315517 | long= -103.191921 | mark= Cyan_pog.svg}} {{location map~ |North America 2 | label = Zacoalco | position = none | lat=20.233333 |long=-103.583333|mark= Red_pog.svg}} {{location map~ | North America 2 | label = Rainbow River | position = none | lat=29.083333 | long= -82.416667 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lake Rousseau| position = none | lat=29.033333 | long= -82.508333 | mark= Red_pog.svg}} {{location map~ |North America 2 | label = McKittrick Tar Seeps | position = none | lat=35.296314 |long=-119.626014 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Perkins Cave | position = none | lat=38.008889 |long=-92.746389 |mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Cleary (Fairbanks) | position = none | lat= 64.846267 | long= -147.734202 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Upper Cleary River Beds | position = none | lat= 65.076281 | long= -147.427406 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Ester (Fairbanks) | position = none | lat= 64.847823 | long= -147.970072 | mark= Purple 8000ff pog.svg}}}} === Regional Paleoecology === ==== ''Arctodus pristinus'' ==== ===== Eastern North America ===== More fossils of ''Arctodus pristinus'' are known from Florida (about 150) than anywhere else.<ref name=":52">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |s2cid=168164209}}</ref> In the [[Gelasian|Early Pleistocene]] of [[Blancan]] [[Florida]], the [[Santa Fe River (Florida)|Santa Fe River 1 site]] (~2.2 Ma), which ''Arctodus pristinus inabited'', indicated a fairly [[Savanna|open grassland]] environment, dominated by [[Flatwoods|longleaf pine flatwoods]]. [[Karst|Karst sinks]] and [[Spring (hydrology)|springs]] were present, very much like modern [[Florida]]. ''Arctodus pristinus'' would have co-existed with megafauna such as terror birds (''[[Titanis]])'', sabertooth cats (''[[Xenosmilus]]''), giant sloth (''[[Eremotherium]]'', ''[[Paramylodon]]'', ''[[Megalonyx]]''), giant armadillos (''[[Holmesina]]'', ''[[Glyptotherium]], [[Pachyarmatherium]]''), [[gomphothere]]s (''[[Rhynchotherium]]'' (''[[Cuvieronius|?Cuvieronius?]]'')), hyenas (''[[Chasmaporthetes|Chasmoporthetes]]''), canids (''[[Borophagus]]'', ''[[Canis lepophagus]]''), peccary (''[[Platygonus]]''), llama (''[[Hemiauchenia]]''), antilocaprids (''[[Capromeryx]]''), and three-toed horse (''[[Nannippus]]''). Smaller fauna included [[condor]]s, [[Rail (bird)|rails]] and [[duck]]s among other small birds, rodents such as [[Erethizon|porcupines]], lizards, snakes, alligators, turtles, and arthropods.<ref>{{Cite journal |last1=Gould |first1=G.C. |last2=Quitmyer |first2=Irvy |date=2005-01-01 |title=Titanis walleri: Bones of contention |url=https://www.researchgate.net/publication/288892560 |journal=Bulletin of the Florida Museum of Natural History |volume=45 |pages=201–229}}</ref><ref>{{Cite journal |last1=MacFadden |first1=Bruce |last2=Labs-Hochstein |first2=Joann |last3=Hulbert |first3=Richard |last4=Baskin |first4=Jon |date=2007-02-01 |title=Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange |url=https://www.researchgate.net/publication/249521166 |journal=Geology |volume=35 |issue=2 |page=123 |bibcode=2007Geo....35..123M |doi=10.1130/G23186A.1}}</ref> The evolution of ''Arctodus simus'', competition with ''[[Tremarctos floridanus]]'' and [[American black bear|black bears]] (both of which only appear in [[Florida]] in the [[Late Pleistocene]]),<ref name=":52" /> and possibly the transitioning of [[Pleistocene]] [[Florida]] from a hot, wet, densely forested habitat to a still hot, but drier and much more open biome are thought to be factors behind the gradual disappearance of ''Arctodus pristinus'' in the [[Chibanian|Middle Pleistocene]] (300,000 BP).<ref name=":02"/><ref name=":92"/> ==== ''Arctodus simus'' ==== ===== Mexico ===== Tremarctine bears were dominant in Mexico during the Late Pleistocene, with ''Arctodus simus'' and ''[[Tremarctos floridanus]]'' being plentiful.<ref name=":92"/> ''Arctodus simus'' was limited to the Mexican plateau, which was generally occupied by tropical thorn scrub and scrub woodland.<ref name=":372">{{Cite journal |last=Eng-Ponce |first=Joaquin |date=August 2021 |title=Reconstruccion paeloambiental del yacimiento La Cinta-Portalitos, Michoacan-Guanajuato, Mexico (thesis) |url=http://bibliotecavirtual.dgb.umich.mx:8083/xmlui/bitstream/handle/DGB_UMICH/6432/FB-M-2021-0909.pdf |journal=Faculty of Biology, Universidad Michoacana de San Nicolás de Hidalgo}}</ref><ref name=":472">{{Cite journal |last1=University of Geneva, Switzerland |last2=Ray |first2=N. |last3=Adams |first3=J.M. |date=2001 |title=A GIS-based Vegetation Map of the World at the Last Glacial Maximum (25,000-15,000 BP) |url=http://intarch.ac.uk/journal/issue11/rayadams_index.html |journal=Internet Archaeology |issue=11 |doi=10.11141/ia.11.2}}</ref> An ''Arctodus simus'' individual from [[Cedral, San Luis Potosí|Cedral]], [[San Luis Potosí]], inhabited closed vegetation, based on the individual's [[Δ13C|''δ''<sup>13</sup>C]] signature. Consuming C3 resources, its' diet may have incorporated contemporaneous C3 specialists such as [[tapir]], [[Hemiauchenia|llamas]], [[Camelops|camels]], and [[Nothrotheriops|Shasta ground sloth]]'','' likely along with browsed vegetation. Fauna which visited closed areas at Cedral include ''[[Paramylodon]]'', [[Platygonus|peccaries]], some horses, [[mastodon]], and occasionally ''[[Glyptotherium]]'', ''[[Megalonyx]]'', bison, [[Dire wolf|dire wolves]], [[American lion]]s and [[Columbian mammoth|Colombian mammoths]]. The site, incorporating trees, herbs and cacti, hosted an open [[gallery forest]] near to [[Savanna|grassland]] or [[Shrubland|scrub]] with a [[Humid subtropical climate|humid climate]]. This [[Savanna|forest-savanna mosaic]], supporting a diverse mammalian herbivore and carnivore fauna, was part of the wider [[Mesic habitat|mesic]] savanna and [[Pinyon–juniper woodland|piñon–juniper woodland]] ecoregion which ''Arctodus'' inhabited in the [[Late Pleistocene]] [[Mexican Plateau|central Mexico]] and [[Southwestern United States|southwestern USA]].<ref name=":410"/><ref>{{Cite book |last=Harris |first=Arthur |url=https://www.researchgate.net/publication/265165536 |title=Pleistocene Vertebrates of Southwestern USA and Northwestern Mexico |date=2014-08-30}}</ref><ref>{{Cite journal |last=Harris |first=Arthur H. |title=Reconstruction of Mid Wisconsin Environments in Southern New Mexico |url=https://www.wipp.energy.gov/library/cra/2009_cra/references/Others/Harris_1987_Reconstruction_of_Mid_Wisconsin_Environments.pdf |journal=National Geographic Research}}</ref> At [[Lake Cuitzeo|La Cinta-Portalitos]] ([[Michoacán]]/[[Guanajuato]]) in the Trans-Mexican Volcanic Belt, prime habitat for ''Arctodus simus'' was the closed temperate forests of the [[Madrean pine–oak woodlands]], dominated by [[pine]]s, [[oak]]s, [[hornbeam]]s, and ferns (''[[Polypodium]]'' & ''[[Pecluma]]''). Associated fauna primarily found in this habitat include [[Allen's cotton rat|''Sigmodon'']], ''[[Aztlanolagus]]'', [[ocelot]]s, [[gray fox]], ''Hemiauchenia'', pronghorns ([[Capromeryx minor|''Capromeryx'']], ''[[Stockoceros]]'', ''[[Tetrameryx]]''), [[cottontail rabbit]]s, [[bobcat]]s, ground sloths (''Nothrotheriops'', ''Megalonyx)'', ''[[Smilodon|Smilodon fatalis]]'' and ''Panthera atrox''. Today, these high-humidity forests are found between 2500-2800m altitude- however, in the Late Pleistocene, they were found at less than 2000m altitude. ''Tremarctos floridanus'' at this locality, on the other hand, inhabited [[gallery forest]]s and their wetlands, along with [[white-tailed deer]], [[Neochoerus aesopi|capybaras]], ''[[Pampatherium]]'', [[Equus (genus)|horses]], and ''[[Cuvieronius]]''.<ref name=":372" /> Similar highland ''Arctodus simus'' remains have been recovered from [[Zacoalco de Torres|Zacoalco]], [[Hueyatlaco|Valsequillo]], and [[Tequixquiac]].<ref>{{Cite journal |last=Lucas |first=Spencer G. |date=January 2008 |title=Late Pleistocene Vertebrate Fossil Assemblages From Jalisco, Mexico |url=https://www.researchgate.net/publication/281862788 |journal=Neogene Mammals. New Mexico Museum of Natural History and Science |volume=Bulletin 44 |pages=51–64 |via=ResearchGate}}</ref><ref>{{Cite journal |last=Hibbard |first=Claude W. |date=18 February 1955 |title=Pleistocene Vertebrates from the Upper Becerra (Becerra Superior) Formation, Valley of Tequixquiac, Mexico, with Notes on Other Pleistocene Forms |journal=Contributions from the Museum of Paleontology |volume=XII |issue=5 |pages=47–96 |hdl=2027.42/48290 |url=http://deepblue.lib.umich.edu/handle/2027.42/48290 |language=en-US}}</ref> ===== Western USA ===== [[File:North_Slope_Santa_Ynez_Mtns.jpg|thumb|''Arctodus simus'' inhabited Californian savannas for over a million years.]] With over 50% (22/38) of specimens found in the contiguous United States from the terminal Pleistocene (<40,000 BP), the Western USA was highly productive habitat for ''Arctodus simus''.<ref name=":92" /> In particular, the [[Pacific Mountain System]] seems to represent a cradle of evolution for ''Arctodus simus''. The earliest finds of ''Arctodus simus'' are from California, from early and middle [[Irvingtonian]] age sites such as [[Vallecito Creek (California)|Vallecito Creek]], Irvington, Riverside, and Fairmead.<ref name=":46" /><ref>{{Cite journal |last=Cassiliano |first=Michael L. |date=1999 |title=Biostratigraphy of Blancan and Irvingtonian Mammals in the Fish Creek-Vallecito Creek Section, Southern California, and a Review of the Blancan-Irvingtonian Boundary |url=https://www.jstor.org/stable/4523978 |journal=Journal of Vertebrate Paleontology |volume=19 |issue=1 |pages=169–186 |doi=10.1080/02724634.1999.10011131 |jstor=4523978 |issn=0272-4634}}</ref><ref>{{Cite book |last=Firby |first=Jean Brower |url=https://books.google.com/books?id=qOdKAQAAMAAJ |title=Revision of the Middle Pleistocene Irvington Fauna of California |date=1968 |publisher=University of California |language=en}}</ref><ref>{{Cite book |last1=Dundas |first1=Robert G. |last2=Chatters |first2=James C. |date=2013-01-01 |chapter=The mid-Irvingtonian Fairmead Landfill fossil site, Madera County Paleontology Collection, and Fossil Discovery Center of Madera County, California |editor=Keith Putirka |title=Geologic Excursions from Fresno, California, and the Central Valley |pages=63–78 |publisher=Geological Society of America |language=en |doi=10.1130/2013.0032(04)|isbn=978-0-8137-0032-8 }}</ref> Evidence from Inland California suggests that despite the shift to aridified environments from the Early to Late Pleistocene of California (1.1Ma to ~15,000 BP), ''Arctodus simus'' remained consistent with the consumption of C3 resources. This period saw the evolution from wetter mixed woodland-grassland and marsh/prairie C3 dominated environs at Irvington and Fairmead, to the more arid, mixed C3-C4 savannas of the McKittrick Tar Pits. Whereas [[jaguar]]s, ''[[Homotherium]]'', ''[[American cheetah|Miracinonyx]]'' and ''Smilodon'' ultimately transitioned to ''Panthera atrox'' and [[coyote]]s in the local predator guild, only dire wolves and ''Arctodus simus'' remained ever present. Foraging opportunities would have been plentiful for ''Arctodus'', with grasses, [[Chenopodioideae|chenopods]], ''[[Xanthium]]'', [[Typhaceae|cattails]], [[Cyperaceae|sedges]], [[willow]], [[oak]], [[spruce]], [[juniper]], and [[Artemisia (plant)|sagebrush]] at Fairmead, and [[pine]]s, [[juniper]], [[Atriplex|saltbush]], [[Arctostaphylos|manzanita]], and [[Echinocystis|wild cucumber]] at McKittrick.<ref name=":232" /> To what extent ''Arctodus'' fed on this vegetation, versus consuming generalists and specialized browsers such as deer ([[Elk|''Cervus'']] & ''[[Odocoileus]]''), camelids (''Hemiauchenia'' & ''Camelops''), ''Paramylodon'', and [[Platygonus|peccaries]] can be clued from the [[La Brea Tar Pits]]. Microwear and general wear patterns on the teeth of recovered from ''Arctodus'' specimens are most similar to the herbivorous spectacled bear, and suggest that they avoided hard/brittle foods, and had a more specialized diet than black bears recovered from the same site. Should ''Arctodus'' have also been a predator, competition with closed habitat, browser specialists would have included ''Smilodon'' and ''Panthera atrox'' in Late Pleistocene inland California.<ref name=":232" /><ref>{{Cite journal |last=Feranec |first=Robert S |date=November 2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |url=https://www.researchgate.net/publication/255728816 |journal=Radiocarbon |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |via=ResearchGate}}</ref><ref>{{Cite journal |last1=Springer |first1=Kathleen |last2=Scott |first2=Eric |last3=Murray |first3=Lyndon K. |last4=Sagebiel |first4=James |date=2009 |title=The Diamond Valley Lake local fauna: late Pleistocene vertebrates from inland southern California |editor=Albright, L. B. III |journal=Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne |url=https://www.academia.edu/218818}}</ref> Many more finds come from across California, and Oregon,<ref>{{Cite web |last=Yumpu.com |title=LATE PLEISTOCENE AIRPORT LANE FOSSIL SITE, LA GRANDE ... |url=https://www.yumpu.com/en/document/view/12116022/late-pleistocene-airport-lane-fossil-site-la-grande- |access-date=2022-07-17 |website=yumpu.com |language=en}}</ref><ref>{{Cite journal |last1=Van Tassell |first1=Jay |last2=Rinehart |first2=John |last3=Mahrt |first3=Laura |date=June 2014 |title=Late Pleistocene Airport Lane fossil site, La Grande, northeast Oregon |url=https://www.oregongeology.org/pubs/OG/OGv70n01_print.pdf |journal=Oregon Geology |volume=70 |issue=1 |pages=3–13 |via=Oregon Department of Geology and Mineral Studies}}</ref><ref>{{Cite web |title=The Spokesman-Review - Google News Archive Search |url=https://news.google.com/newspapers?nid=1314&dat=19280626&id=PGpWAAAAIBAJ&sjid=vvMDAAAAIBAJ&pg=5453,5034598 |access-date=2022-07-20 |website=news.google.com}}</ref> where the semi-arid woodland/scrub transitioned to [[Forest steppe|forest-steppe]].<ref name=":472" />[[File:Paleontological_landscape_painting,_White_Sands_National_Park,_United_States.jpg|thumb|A reconstruction of Rancholabrean New Mexico ([[White Sands National Park|White Sands]]).|left]]The [[Intermontane Plateaus|Intermontane Plateau]], which largely hosted subalpine parkland,<ref name=":472" /> had the highest number of ''Arctodus simus'' specimens south of the ice sheets. The region has yielded some of the largest specimens of ''A. simus,'' including, what was once the largest specimen on record, from Bonneville, Utah.<ref>{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |url=https://www.jstor.org/stable/3628418 |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 |issn=0022-8443}}</ref> In contrast with other parts of North America, the plateau received more rainfall during the Late Pleistocene, because glacially cooled air collided with hot desert air, resulting in increased precipitation and cool cloudy conditions. As a result, this greatly expanded the range of woodlands where desert exists today, with [[pluvial lake]]s being abundant in the south-west. The mid-[[Wisconsin glaciation|Wisconsian]] U-Bar cave (New Mexico) was populated by fauna typically found in cooler and more mesic habitats, particularly habitats characterized by a notable pulse of cool-season precipitation, relatively warm winters, and limited warm-season moisture. [[Artemisia tridentata|Sagebrush]], grasses, and woodland vegetation suggests cooler summers and a more pronounced emphasis on cool-season precipitation than in lowland New Mexico (Dry Cave). This more xeric and warmer climate contrasts with the sagebrush steppe-woodland of the Last Glacial Maximum. Notable fauna which lived alongside ''Arctodus simus'' included Shasta ground sloth, [[Euceratherium|shrub-ox]], pronghorns (''Stockoceros,'' ''Capromeryx''), ''Camelops'', ''Odocoileus'', horses, ''Lynx'', [[Cougar|puma]], black bear, [[Oreamnos|mountain goats]]'','' prairie dogs, and [[Stock's vampire bat]].<ref>{{Cite journal |last=Harris |first=Arthur H. |date=November 1985 |title=Preliminary report 0n the vertebrate fauna of U-Bar Gave, Hidalgo County, New Mexico |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/7/n4/nmg_v7_n4_p74.pdf |journal=New Mexico Geology |pages=74–84}}</ref><ref>{{Cite web |title=U-Bar Cave |url=https://www.utep.edu/leb/pleistnm/sites/ubarcave.htm |access-date=2022-07-24 |website=www.utep.edu}}</ref> Dire wolves were also found in association with ''Arctodus simus'' at U-Bar cave, along with Conkling Cavern- both species are the most common carnivorans of Rancholabrean New Mexico.<ref>{{Cite book |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=S--oDQAAQBAJ&dq=Rock+Creek+texas+arctodus&pg=PA296 |title=Vertebrate Paleontology in New Mexico: Bulletin 68 |last2=Sullivan |first2=Robert M. |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref> Beyond New Mexico,<ref>{{Cite journal |last1=Schultz |first1=C. Bertrand |last2=Howard |first2=Edgar B. |last3=Schultz |first3=C. Bernard |date=1935 |title=The Fauna of Burnet Cave, Guadalupe Mountains, New Mexico |url=https://www.jstor.org/stable/4064215 |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=87 |pages=273–298 |jstor=4064215 |issn=0097-3157}}</ref><ref>{{Cite journal |last=Harris |first=Arthur H. |date=1993 |title=Quaternary Vertebrates of New Mexico |url=https://www.utep.edu/leb/curators/QuatVert.pdf |journal=Vertebrate Paleontology in New Mexico, New Mexico Museum of Natural History and Science |volume=Bulletin 2 |pages=179–197}}</ref><ref>{{Cite journal |last1=Harris |first1=A. H. |last2=Findley |first2=J. S. |date=1964-01-01 |title=Pleistocene-Recent fauna of the Isleta caves, Bernalillo County, New Mexico |url=http://www.ajsonline.org/cgi/doi/10.2475/ajs.262.1.114 |journal=American Journal of Science |language=en |volume=262 |issue=1 |pages=114–120 |doi=10.2475/ajs.262.1.114 |bibcode=1964AmJS..262..114H |issn=0002-9599}}</ref><ref>{{Cite conference |last1=Morgan |first1=Gary S. |last2=Lucas |first2=Spencer G. |last3=Love |first3=David |date=2009 |title=Cenozoic vertebrates from Socorro County, central New Mexico |editor=Virgil Lueth |editor2=Spencer G. Lucas |editor3=Richard M. Chamberlin |book-title=New Mexico Geological Society Fall Field Conference Guidebook: 60 Geology of the Chupadera Mesa |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/60/60_p0321_p0336.pdf |pages=321–336}}</ref><ref>{{Cite journal |last=Morgan |first=Gary S. |last2=Lucs |first2=Spencer G. |date=2005-01-01 |title=Pleistocene vertebrates from southeastern New Mexico |url=https://digitalcommons.usf.edu/kip_articles/4347 |journal=KIP Articles}}</ref> other important specimens have also been found in Arizona, Idaho, Montana,<ref>{{Cite journal |last=Hill |first=Christopher L. |date=2006-01-01 |title=Stratigraphic and geochronologic contexts of mammoth (Mammuthus) and other Pleistocene fauna, Upper Missouri Basin (northern Great Plains and Rocky Mountains), U.S.A. |url=https://www.sciencedirect.com/science/article/pii/S104061820500056X |journal=Quaternary International |series=Third International Mammoth Conference, Dawson, Yukon |language=en |volume=142-143 |pages=87–106 |doi=10.1016/j.quaint.2005.03.007 |bibcode=2006QuInt.142...87H |issn=1040-6182}}</ref> Nevada,<ref>{{Cite journal |last1=Emslie |first1=Steven D. |last2=Mead |first2=Jim I. |date=August 2020 |title=The Age and Vertebrate Paleontology of Labor-of-Love Cave, White Pine County, Nevada |url=https://bioone.org/journals/western-north-american-naturalist/volume-80/issue-3/064.080.0301/The-Age-and-Vertebrate-Paleontology-of-Labor-of-Love-Cave/10.3398/064.080.0301.full |journal=Western North American Naturalist |volume=80 |issue=3 |pages=277–291 |doi=10.3398/064.080.0301 |s2cid=225958789 |issn=1527-0904}}</ref> and Utah. The Intermontane Plateau extended deep into Mexico, where it demarked the southernmost habitat of ''Arctodus simus''.[[File:Canis_dirus_3484.jpg|thumb|Dire wolves are often found at the same localities as ''Arctodus simus'', and were the most common predator of western North America.]]Comparatively, the [[Rocky Mountain System]] had the fewest number of specimens of ''Arctodus simus'' in western North America. However, one of the youngest dated ''Arctodus simus'' is from a cave near Huntington Reservoir, Utah, which sits at an elevation of 2,740m (~9,000&nbsp;ft),. The central and southern Rocky Mountains may have acted as refugia for ''Arctodus simus'', in addition to other contemporary high-elevation alpine fauna such as Colombian mammoths, [[mastodon]], [[Equus conversidens|horses]], and [[Bison latifrons|giant bison]] ≤11,400 BP (10,000 <sup>14</sup>C BP).<ref name=":382" /><ref name=":9" /><ref name=":442">{{Cite journal |last=Stuart |first=Anthony John |date=May 2015 |title=Late Quaternary megafaunal extinctions on the continents: a short review: LATE QUATERNARY MEGAFAUNAL EXTINCTIONS |url=https://onlinelibrary.wiley.com/doi/10.1002/gj.2633 |journal=Geological Journal |language=en |volume=50 |issue=3 |pages=338–363 |doi=10.1002/gj.2633|s2cid=128868400 }}</ref> Other remains have been found from [[Natural Trap Cave]] and Little Box Elder Cave in Wyoming,<ref>{{Cite journal |last=Long |first=C. A. |date=1971 |title=Significance of the Late Pleistocene fauna from the Little Box Elder Cave, Wyoming, to studies of zoogeography of recent mammals |url=https://www.semanticscholar.org/paper/Significance-of-the-Late-Pleistocene-fauna-from-the-Long/f20528d15f55b41a3f6487726c65698286febf4b |s2cid=55933331 |language=en}}</ref> and Montana.<ref>{{Cite journal |last1=Smith |first1=Larry N. |last2=Hill |first2=Christopher L. |last3=Reiten |first3=Jon |title=Quaternary and Late Tertiary of Montana: Climate, Glaciation, Stratigraphy, and Vertebrate Fossils |url=https://mbmg.mtech.edu/pdf/geologyvolume/Smith_QuaternaryMontanaFinal.pdf |journal=Montana Bureau of Mines and Geology Publication 122 |volume=1: Geologic History |via=Montana Bureau of Mines and Geology}}</ref> ===== Interior USA ===== The [[Interior Plains]] were composed of temperate steppe grassland,<ref name=":472" /> and among the specimens yielded from this region is the largest ''Arctodus simus'' currently on record, from the banks of the Kansas river. The [[Irvingtonian]] age Doeden gravel pits in Montana preserves an open grassland habitat, with riparian woodlands, and likely some shrublands.<ref>{{Cite web |title=Abstract: PLEISTOCENE VERTEBRATES FROM THE DOEDEN LOCAL FAUNA (ILLINOIAN/SANGAMONIAN?), YELLOWSTONE RIVER VALLEY, EASTERN MONTANA (Rocky Mountain - 55th Annual Meeting (May 7-9, 2003)) |url=https://gsa.confex.com/gsa/2003RM/webprogram/Paper53111.html |access-date=2022-07-20 |website=gsa.confex.com}}</ref> ''Arctodus simus'' co-existed with ground sloths (''Megalonyx'', ''Paramylodon''), Pacific mastodon, [[Camelops|camels]], and oxen (''[[Bootherium]]'').<ref>{{Cite journal |last1=McDonald |first1=Andrew T. |last2=Atwater |first2=Amy L. |last3=Dooley Jr |first3=Alton C. |last4=Hohman |first4=Charlotte J.H. |date=2020-11-16 |title=The easternmost occurrence of Mammut pacificus (Proboscidea: Mammutidae), based on a partial skull from eastern Montana, USA |journal=PeerJ |volume=8 |pages=e10030 |doi=10.7717/peerj.10030 |issn=2167-8359 |pmc=7676352 |pmid=33240588}}</ref><ref>{{Cite journal |last1=Hill |first1=Christopher L |last2=Wilson |first2=Michael C |date=2002 |title=Fossil Arctodus from the Doeden Local Fauna (Illinoian/Sangamonian?), Eastern Montana |url=https://www.researchgate.net/publication/270216214 |journal=Unknown |via=ResearchGate}}</ref><ref name=":4">{{Cite journal |last1=Hill |first1=Christopher L. |last2=Wilson |first2=Mike C. |date=2000 |title=The Doeden Local Fauna (Illinoian/Sangamonian?), Eastern Montana |url=https://www.researchgate.net/publication/270216333 |journal=Unknown |pages=140–142 |via=ResearchGate}}</ref> As bison were yet to migrate into North America, Colombian mammoths and horses dominated these Sangamonian grasslands.<ref>{{Cite journal |last1=Froese |first1=Duane |last2=Stiller |first2=Mathias |last3=Heintzman |first3=Peter D. |last4=Reyes |first4=Alberto V. |last5=Zazula |first5=Grant D. |last6=Soares |first6=André E. R. |last7=Meyer |first7=Matthias |last8=Hall |first8=Elizabeth |last9=Jensen |first9=Britta J. L. |last10=Arnold |first10=Lee J. |last11=MacPhee |first11=Ross D. E. |date=2017-03-28 |title=Fossil and genomic evidence constrains the timing of bison arrival in North America |journal=Proceedings of the National Academy of Sciences |language=en |volume=114 |issue=13 |pages=3457–3462 |doi=10.1073/pnas.1620754114 |issn=0027-8424 |pmc=5380047 |pmid=28289222|bibcode=2017PNAS..114.3457F |doi-access=free }}</ref> Additional [[Irvingtonian]] remains have been recovered from Arkalon in Kansas, Hay Springs in Nebraska, and Rock Creek in Texas.[[File:Wildflowers_on_ranchland,_State_Highway_965,_Llano_County,_Texas,_USA_(13_April_2012).jpg|thumb|221x221px|''Arctodus'' also roamed the southern mixed grasslands of Texas.|left]]Whereas the northern plains aridified into cold steppe in the [[Rancholabrean]] age (e.g. [[The Mammoth Site|Mammoth site]], South Dakota),<ref name=":242">{{Cite journal |last=Louguet-Lefebvre |first=Sophie |date=2013-12-15 |title=The Columbian mammoths from the Upper Pleistocene of Hot Springs (South Dakota, United States) |url=https://journals.openedition.org/paleo/2861 |journal=PALEO. Revue d'archéologie préhistorique |language=en |issue=24 |pages=149–171 |doi=10.4000/paleo.2861 |issn=1145-3370}}</ref> the southern plains were a parkland with riparian deciduous forests (e.g. [[Celtis|hackberry]]), and large expanses of mixed grass prairie grasslands grading into wet meadows. At [[Lubbock Lake Landmark|Lubbock Lake]] on the [[Llano Estacado]], Texas, above freezing/mild winters and cool summers highlighted a regional climate of reduced seasonality and stable humidity in the latest Pleistocene.<ref name=":252">{{Cite journal |last=Johnson |first=Eileen |date=1986 |title=Late Pleistocene and Early Holocene Vertebrates and Paleoenvironments on the Southern High Plains, U.S.A. |url=https://www.erudit.org/en/journals/gpq/1900-v1-n1-gpq1924/032647ar.pdf |journal=Géographie physique et Quaternaire |volume=40 |issue=3 |pages=249–261|doi=10.7202/032647ar }}</ref> Overall, ''Arctodus simus'', grey wolves and coyotes were part of a predator guild throughout the Rancholabrean great plains, and were joined by Colombian mammoths, camels, ''Hemiauchenia'', and American pronghorns. In the northern plains, woolly mammoths also ranged across the steppe, whereas in the south, ''Smilodon'', dire wolves, grey fox and red fox in the south preyed upon horses prairie dogs, horses (''Equus'' & ''[[Haringtonhippus]]''), peccaries, ''Odocoileus'', ''Capromeryx'', ''Bison antiquus'' and ''Holmesina''.<ref name=":242" /><ref name=":252" /> Beyond Texas,<ref>{{Cite journal |last=Smith |first=Felisa A. |last2=Tomé |first2=Catalina P. |last3=Elliott Smith |first3=Emma A. |last4=Lyons |first4=S. Kathleen |last5=Newsome |first5=Seth D. |last6=Stafford |first6=Thomas W. |date=February 2016 |title=Unraveling the consequences of the terminal Pleistocene megafauna extinction on mammal community assembly |url=https://onlinelibrary.wiley.com/doi/10.1111/ecog.01779 |journal=Ecography |language=en |volume=39 |issue=2 |pages=223–239 |doi=10.1111/ecog.01779 |issn=0906-7590}}</ref> ''Arctodus'' has also been found from the Kaw River and [[Meade County, Kansas|Jinglebob]] in Kansas.<ref>{{Cite journal |last=Taylor |first=D. W. |date=1960 |title=Late Cenozoic molluscan faunas from the High Plains |url=https://pubs.er.usgs.gov/publication/pp337 |journal=Professional Paper |doi=10.3133/pp337 |issn=2330-7102}}</ref> In the lowlands in the eastern Interior plains, the plains transitioned to closed habitat. At the terminal Pleistocene [[Sheriden Cave]], Ohio, a mosaic habitat consisting of marsh, open woodland, and patchy grassland was home to ''Arctodus simus'', ''[[Cervalces scotti]]'', caribou, peccaries ([[Platygonus compressus|''Platygonus'']], [[Long-nosed peccary|''Mylohyus'']]), [[Castoroides|giant beaver]], [[North American porcupine|porcupine]], and [[American marten|American pine marten]].<ref name=":282">{{Cite journal |last=Tankersley |first=Kenneth B. |date=26 May 1997 |title=Sheriden: A Clovis cave site in eastern North America |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1520-6548(199709)12:6%3C713::AID-GEA9%3E3.0.CO;2-1 |journal=Geoarchaeology|volume=12 |issue=6 |pages=713–724|doi=10.1002/(SICI)1520-6548(199709)12:6<713::AID-GEA9>3.0.CO;2-1 }}</ref><ref name=":322">{{Cite journal |last1=Redmond |first1=Brian G. |last2=Tankersley |first2=Kenneth B. |date=10 February 2005 |title=Evidence of Early Paleoindian Bone Modification and Use at the Sheriden Cave Site (33WY252), Wyandot County, Ohio |url=https://www.cambridge.org/core/product/identifier/S0002731600039020/type/journal_article |journal=American Antiquity |language=en |volume=70 |issue=3 |pages=503–526 |doi=10.2307/40035311 |jstor=40035311 |s2cid=162034505 |issn=0002-7316}}</ref> Similar remains have been found in Indiana and Iowa.<ref>{{Cite web |title=Giant Short-Faced Bear {{!}} University of Iowa Museum of Natural History - The University of Iowa |url=https://mnh.uiowa.edu/giant-short-faced-bear |access-date=2022-07-18 |website=mnh.uiowa.edu |language=en}}</ref> To the south, the [[Interior Highlands]] had a very high density of ''Arctodus simus'' specimens (second only to the black bear),<ref name=":92" /> due to the high rate of preservation in the cave-rich region. Sympatry between the two species is most apparent in Missouri- ''Arctodus simus'' has been found in association with black bears at Riverbluff, Bat and Big Bear caves.<ref>{{Cite journal |last=Hawksley |first=Oscar |date=July 1965 |title=Short-Faced Bear (Arctodus) Fossils from Ozark Caves |url=https://caves.org/pub/journal/NSS%20Bulletin/vol%2027%20part%203.pdf |journal=Bulletin of the National Speleological Society |volume=27 |issue=3 |pages=77–92}}</ref> At [[Riverbluff Cave]], the most abundant claw marks are from ''Arctodus simus''. Some being up to 4 meters high on the cave walls, they are most abundant at the bear beds and their associated passageways, indicating a close relationship with denning. Other impressions found include claw marks from a large cat (either ''Panthera atrox'' or ''Smilodon fatalis'') and ''Platygonus'' trackways.<ref name=":1" /> Big Bear Cave preserves fossilized hair associated with ''Arctodus''.<ref name=":210" /> During the Last Glacial Maximum, both bears were joined by dire wolves, coyotes, jaguars, [[snowshoe hare]], [[groundhog]]s and [[beaver]]s at Bat Cave, which also records thousands of ''Platygonus'' remains. These fauna inhabited well-watered forest-grassland ecotone with a strong taiga influence. These open woodlands were dominated by [[pine]]s and [[spruce]], and to a lesser extent by [[oak]]s''.''<ref>{{Cite journal |last=Woodruff |first=Aaron L. |date=2016 |title=Description, Taphonomy, and Paleoecology of the Late Pleistocene Peccaries (Artiodactyla: Tayassuidae) from Bat Cave, Pulaski County, Missouri |url=https://dc.etsu.edu/cgi/viewcontent.cgi?article=4444&context=etd |journal=Department of Geosciences, East Tennessee State University |issue=Paper 3051 |via=East Tennessee State University Digital Commons @ East Tennessee State University}}</ref><ref>{{Cite journal |last1=Woodruff |first1=Aaron L. |last2=Schubert |first2=Blaine W. |date=2019-07-04 |title=Seasonal denning behavior and population dynamics of the late Pleistocene peccary Platygonus compressus (Artiodactyla: Tayassuidae) from Bat Cave, Missouri |journal=PeerJ |volume=7 |pages=e7161 |doi=10.7717/peerj.7161 |issn=2167-8359 |pmc=6612422 |pmid=31308997}}</ref><ref>{{Cite journal |last1=Hawksley |first1=Oscar |last2=Reynolds |first2=Jack F. |last3=Foley |first3=Robert F. |date=July 1973 |title=Pleistocene Vertebrate Fauna of Bat Cave, Pulaski County, Missouri |url=https://caves.org/pub/journal/NSS%20Bulletin/Vol%2035%20num%203.pdf |journal=Bulletin of the National Speleological Society |volume=35 |issue=3 |pages=61–87}}</ref><ref>{{Cite journal |last=Santucci |first=Vincent L. |last2=Kenworthy |first2=Jason |last3=Kerbo |first3=Ron |date=2022-01-18 |title=An inventory of paleontological resources associated with national park service caves |url=https://digitalcommons.usf.edu/kip_articles/271 |journal=KIP Articles}}</ref> However, evidence from Riverbluff Cave suggests that the region occasionally cycled through drier, grassier periods in the last 55,000 years.<ref>{{Cite web |last1=Smith |first1=Matthew D |last2=Dorale |first2=Jeffrey A |last3=Johnson |first3=Aaron W |last4=Forir |first4=Matthew D |date=2013 |title=A speleothem record of paleoenvironmental change from Riverbluff Cave, Missouri, U.S.A |url=https://iro.uiowa.edu/esploro/outputs/abstract/A-speleothem-record-of-paleoenvironmental-change/9984240795902771 |access-date=2022-07-26 |website=iro.uiowa.edu}}</ref>[[File:Mountain-type_Woodland_Caribou.jpg|thumb|Open boreal woodlands provided adequate resources for ''Arctodus simus''.]] ===== Eastern USA ===== Compared to other regions, ''Arctodus simus'' was relatively rare in eastern North America.<ref name=":92" /> To the north, the [[Appalachian Highlands]] were dominated by taiga.<ref name=":472" /> Post-LGM [[Saltville (archaeological site)|Saltville]], Virginia, was a mosaic of grassy/herb laden open areas intermixed with open canopy [[Taiga|boreal woodlands]] (oaks, pines, spruce, birch, firs) and marshes. Inhabiting in this [[C3 carbon fixation|C3]] resource dominated environment were ''Arctodus simus'', mastodon, (southernmost) [[woolly mammoth]]s, oxen (''Bootherium),'' horses, caribou, ground sloths (''Megalonyx''), dire wolves, beavers, ''[[Cervalces]]'', and a variety of warm-adapted reptiles, suggesting that a more mesic and less seasonal climate allowed for the mixing of more typically northern and southern fauna. Heavy bone damage on a mammoth carcass by both dire wolves and ''Arctodus'' suggests a potentially competitive scavenging relationship <ref>{{Cite journal |last=Simpson |first=Emily |date=2019-05-01 |title=Paleoecology and Land-Use of Quaternary Megafauna from Saltville, Virginia |url=https://dc.etsu.edu/etd/3590 |journal=Electronic Theses and Dissertations}}</ref><ref name=":332">{{Cite journal |last1=Schubert |first1=Blaine W. |last2=Wallace |first2=Steven C. |date=August 2009 |title=Late Pleistocene giant short-faced bears, mammoths, and large carcass scavenging in the Saltville Valley of Virginia, USA |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.2009.00090.x |journal=Boreas |language=en |volume=38 |issue=3 |pages=482–492 |doi=10.1111/j.1502-3885.2009.00090.x |s2cid=129612660}}</ref> Additional remains have been found at Island Ford Cave in Virginia, and [[Frankstown Township, Blair County, Pennsylvania|Frankstown]] in Pennsylvania. [[File:Lake Rousseau.JPG|thumb|222x222px|[[Lake Rousseau]], Florida, is the south-eastern most locality which ''Arctodus simus'' is known to have inhabited.|left]] To the south, the [[Atlantic Plain]]s covered a great expanse of lowland, from the open deciduous woodlands of the [[Atlantic coastal plain|Atlantic coast]], to the semi-arid woodland/scrub of Florida, to the spruce-fir conifer forests and open habitat of the [[Gulf Coastal Plain]]. Although scarce, this contrast of habitats highlights the adaptability of ''Arctodus simus''. At the [[Rainbow River]] and [[Lake Rousseau]] localities in Rancholabrean Florida, three ''Arctodus simus'' specimens have been recovered, alongside ''Smilodon'', dire wolves, jaguars, ground sloths (''Paramylodon'', ''Megalonyx''), llamas (''[[Palaeolama]]'', ''Hemiauchenia''), [[Tapirus veroensis|Vero's tapir]], giant beaver, [[capybara]], ''Holmesina'', horses, ''Bison antiquus'', mastodon, Colombian mammoths and ''Tremarctos floridanus'', in a climate similar to today's. That one of the three individuals was a very large, older specimen establishes extreme sexual dimorphism as the explanation behind size differences in ''Arctodus simus''. Furthermore, the abundance of black bears, and particularly Florida short faced bears in Florida, has led to a theorized niche partitioning of ursids in Florida, with ''Tremarctos floridanus'' being herbivorous, and black bears and ''Arctodus simus'' being omnivorous, with ''Arctodus'' being possibly more inclined towards carnivory.<ref name=":02" /> In the [[Black Belt (geological formation)|Black Belt]] of Late Pleistocene [[Mississippi]], a terrestrial [[floodplain]] at [[Trinity, Mississippi|Cedar Creek]] hosted a mixture of grassland and mixed woodlands adapted species (including ''Arctodus simus''). Horses, then bison, are the most numerous of the fauna, but were also joined by Colombian mammoths, coyotes, ''[[Dasypus bellus]]'' and ''Holmesina'' on the plains. Mastodon, ground sloths (''Eremotherium'', ''Megalonyx''), peccaries (''Platygonus'', ''Mylohylus''), deer ([[Elk|''Cervus'']], ''[[White-tailed deer|Odocoileus]]''), lynx, black bear, Florida short-faced bear, [[margay]]s, [[gray fox]], ''Hemiauchenia,'' turkeys and racoons in the open woodlands, with giant beavers, lesser beavers, and capybara inhabiting the marshes. Coyotes and black bears from this locality are unusually small for the Late Pleistocene. Further west, in the [[Mississippi Alluvial Plain (ecoregion)|Mississippi Alluvial Plain]], the fauna ''Arctodus simus'' encountered at [[Lake Whittington|the Bar]], [[Arkansas]] was similar to Saltville, Virginia, with the addition of ''Paleolama'', ''Bison'', ''Mylohyus'', black bears, tapirs, [[manatee]]s and [[alligator snapping turtle]]s. During the Last Glacial Maximum, in part due to glacial meltwaters producing a cold microclimate, boreal forests extended from [[40th parallel north|40° N]] to coastal regions near [[23rd parallel north|23° N]]. Mississippi's boreal forests were dominated by pine, spruce, ash, aspen, oak and hickory, with more deciduous trees and herbs/grasses in the lowlands. However, the presence of the giant tortoise, ''[[Hesperotestudo|Hesperotestudo crassiscutata]]'', in both localities is indicative of mild winters, and limited seasonality.<ref>{{Cite journal |last1=Baghai-Riding |first1=Nina L. |last2=Husley |first2=Danielle B. |last3=Beck |first3=Christine |last4=Blackwell |first4=Eric |date=December 2017 |title=Late Pleistocene Megafauna from Mississippi Alluvium Plain Gravel Bars |url=https://paludicolavertpaleo.files.wordpress.com/2019/11/11-3-baghai-riding-2017.pdf |journal=Paludicola |volume=11 |issue=3 |pages=124–147 |via=Rochester Institute of Vertebrate Paleontology}}</ref><ref>{{Cite journal |last=Ruddell |first=Michael W. |date=December 1999 |title=Quaternary Vertebrate Paleoecology of the Central Mississippi Alluvial Valley; Implications for the Initial Human Occupation |url=https://trace.tennessee.edu/cgi/viewcontent.cgi?article=3184&context=utk_graddiss |journal=Tennessee Research and Creative Exchange |via=University of Tennessee, Knoxville}}</ref><ref>{{Cite journal |last1=Kurtén |first1=Björn |last2=Kaye |first2=John M. |date=March 1982 |title=Late Quaternary Carnivora from the Black Belt, Mississippi |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.1982.tb00519.x |journal=Boreas |language=en |volume=11 |issue=1 |pages=47–52 |doi=10.1111/j.1502-3885.1982.tb00519.x}}</ref><ref>{{Cite journal |last=Kaye |first=John Morgan |date=1974 |title=Pleistocene Sediment and V ocene Sediment and Vertebrate Fossil Associations in the ossil Associations in the Mississippi Black Belt: a Genetic Approach |url=https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=3611&context=gradschool_disstheses |journal=LSU Historical Dissertations and Theses. |volume=2612 |via=Louisiana State University}}</ref> ''Arctodus'', along with Colombian mammoths, seems to have avoided the coastal savannas of the south east, where ''[[Mixotoxodon]]'' was present. Additional finds of south-eastern ''Arctodus simus'' are from Alabama,<ref>{{Cite journal |last1=Ebersole |first1=Jun A. |last2=Ebersole |first2=Sandy M. |date=December 2011 |title=Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Taxa |url=http://almnh.museums.ua.edu/wp-content/uploads/sites/2/2018/12/BALMNH_No_28_2011.pdf |journal=Alabama Museum of Natural History Bulletin |volume=28 |pages=24–25 |via=University of Alabama}}</ref> South Carolina.<ref>{{Cite web |last=apmiller@postandcourier.com |first=Andrew Miller |title=SC diver finds rare prehistoric bear tooth fossil in Cooper River |url=https://www.postandcourier.com/news/sc-diver-finds-rare-prehistoric-bear-tooth-fossil-in-cooper-river/article_c8cf9104-8d7a-11eb-bd4d-af15386d585a.html |access-date=2022-07-09 |website=Post and Courier |language=en}}</ref><ref>{{Cite web |date=2021-04-08 |title=First Record of the Giant Short-Faced Bear (Arctodus simus) in South Carolina |url=https://markgelbart.wordpress.com/2021/04/08/first-record-of-the-giant-short-faced-bear-arctodus-simus-in-south-carolina/ |access-date=2022-07-09 |website=GeorgiaBeforePeople |language=en}}</ref> and Texas.<ref name=":13" /><ref>{{Cite journal |last=Slaughter |first=Bob H. |date=1966 |title=The Moore Pit Local Fauna; Pleistocene of Texas |url=https://www.jstor.org/stable/1301775 |journal=Journal of Paleontology |volume=40 |issue=1 |pages=78–91 |jstor=1301775 |issn=0022-3360}}</ref> ===== Canada ===== [[File:Vashon_Glaciation_Mockup_2016-06-26.png|thumb|On the boundary of the northern glacier.|left]] The vast majority of Canada was glaciated during the Late Pleistocene. However, southern [[Alberta]] may have been spared, providing a tundra ecosystem (at least until the Last Glacial Maximum).<ref>{{Cite journal |last1=Young |first1=Robert R. |last2=Burns |first2=James A. |last3=Smith |first3=Derald G. |last4=Arnold |first4=L. David |last5=Rains |first5=R. Bruce |date=1994-08-01 |title=A single, late Wisconsin, Laurentide glaciation, Edmonton area and southwestern Alberta 2.3.CO;2 |journal=Geology |volume=22 |issue=8 |pages=683–686 |doi=10.1130/0091-7613(1994)022<0683:ASLWLG>2.3.CO;2 |issn=0091-7613}}</ref> ''Arctodus simus'' remains have been recovered from the mid-[[Wisconsin glaciation|Wisconsian]] (~22,000 BP) near Edmonton, forming a predator guild with the gray wolf and American lion. Also present were ''Megalonyx'', horses (''E. conversidens'' & ''E. niobrarensis''), [[Barren-ground caribou|caribou]], [[Camelops|camels]], mammoths (Colombian and woolly), mastodon, bison (''B. priscus'' & ''B. latifrons''), and oxen (''Ovibos'' & ''Bootherium''). The higher diversity of grazers to browsers suggested a more open environment- that the American lion individual was noticeably smaller than its southern contemporaries contrasts with the huge ''Arctodus'' and large wolf specimens.<ref name=":62">{{Cite journal |last1=Burns |first1=James A. |last2=Young |first2=Robert R. |date=1994-02-01 |title=Pleistocene mammals of the Edmonton area, Alberta. Part I. The carnivores |url=http://www.nrcresearchpress.com/doi/10.1139/e94-036 |journal=Canadian Journal of Earth Sciences |language=en |volume=31 |issue=2 |pages=393–400 |doi=10.1139/e94-036 |bibcode=1994CaJES..31..393B |issn=0008-4077}}</ref> The entry to the ice-free corridor to Beringia may have also been near [[Edmonton]], providing a migration pathway to Beringia. ''Arctodus'' remains from similar habitat has also been recovered from Saskatchewan,<ref>{{Cite journal |last=Harington |first=C. R. |date=1973 |title=A Short-Faced Bear From Ice Age Deposits at Lebret, Saskatchewan |url=https://bluejayjournal.ca/index.php/bluejay/article/view/4039 |journal=Blue Jay |language=en |volume=31 |issue=1 |doi=10.29173/bluejay4039 |s2cid=222373512 |issn=2562-5667}}</ref> and from the [[Forest steppe|forest-steppe]] of Late Pleistocene Vancouver Island.<ref name=":156"/><ref>{{Cite journal |last1=Steffen |first1=Martina L. SteffenM L. |last2=Harington |first2=C. R. HaringtonC R. |date=2010-07-23 |title=Giant short-faced bear (Arctodus simus) from late Wisconsinan deposits at Cowichan Head, Vancouver Island, British Columbia |url=https://cdnsciencepub.com/doi/10.1139/E10-018 |journal=Canadian Journal of Earth Sciences |volume=47 |issue=8 |pages=1029–1036 |language=en |doi=10.1139/E10-018|bibcode=2010CaJES..47.1029S }}</ref> ''Arctodus'' was a scarce member of the Pleistocene fauna of southern Canada- extant herbivorous bears are browsers, not grazers, so the scarcity of ''Arctodus'' in mid-latitude North America may be due to a lack of suitable vegetation on the steppe. On the other hand, should ''Arctodus simus'' have been a large and strict carnivore, perhaps ''Arctodus simus'' would never have been very numerous in an open ecosystem.<ref name=":62" /> ===== Beringia ===== [[File:Wolf_with_Caribou_Hindquarter.jpg|thumb|230x230px|''Arctodus'' is suggested to have had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|Beringian wolves]], akin to modern [[Wolf|wolves]] and [[brown bear]]s.]] Mostly isolated by the Cordilleran and Laurentide ice sheets, Beringia is considered ecologically separate to the rest of North America, being largely an extension of the Eurasian [[mammoth steppe]].<ref>{{Citation |last1=David Webb |first1=S. |title=Vertebrate paleontology |date=2003 |url=https://linkinghub.elsevier.com/retrieve/pii/S157108660301025X |work=Developments in Quaternary Sciences |volume=1 |pages=519–538 |publisher=Elsevier |language=en |doi=10.1016/s1571-0866(03)01025-x |isbn=978-0-444-51470-7 |access-date=2022-06-28 |last2=Graham |first2=Russell W. |last3=Barnosky |first3=Anthony D. |last4=Bell |first4=Christopher J. |last5=Franz |first5=Richard |last6=Hadly |first6=Elizabeth A. |last7=Lundelius |first7=Ernest L. |last8=Gregory McDonald |first8=H. |last9=Martin |first9=Robert A.}}</ref> However, due to the occasional opening of an ice-free corridor, and the migration barrier of the Beringian gap, meant that Eastern Beringia ([[Alaska]] and the [[Yukon]]) supported a unique assemblage of fauna, with many endemic North American fauna flourishing (such as ''Arctodus simus'') within a mostly Beringian ecosystem.<ref>{{Cite journal |last1=Churcher |first1=C. S. |last2=Morgan |first2=A. V. |last3=Carter |first3=L. D. |date=2011-02-08 |title=Arctodus simus from the Alaskan Arctic Slope |url=https://cdnsciencepub.com/doi/10.1139/e93-084 |journal=Canadian Journal of Earth Sciences |volume=30 |issue=5 |pages=1007–1013 |language=en |doi=10.1139/e93-084}}</ref> This mostly open and treeless steppe-tundra, dominated by grasses, sedges, ''Artemisia spp.'', and a range of other forbs had a cold, dry climate, which prevented glaciation. Currently, all specimens of ''Arctodus'' in [[Beringia]] have been dated to a 27,000 year window (50,000 BP~23,000 BP) from Eastern Beringia.<ref name=":19" /><ref name=":156"/> However, additional undated remains may be of [[Sangamonian]] age.<ref>{{Cite journal |last=Harington |first=C. R. |date=1980 |title=Radiocarbon Dates on Some Quaternary Mammals and Artifacts from Northern North America |url=https://www.jstor.org/stable/40509084 |journal=Arctic |volume=33 |issue=4 |pages=815–832 |doi=10.14430/arctic2598 |jstor=40509084 |issn=0004-0843}}</ref> The [[Alaska North Slope|North Slope]] of Alaska <40,000 BP (Ikpikpuk and Titaluk rivers) preserves an upland and floodplain environment, with horses, bison then caribou being the most populous herbivores, and woolly mammoths, muskoxen, elk and [[saiga antelope]] more scarce. Cave lions, bears (''Ursus arctos'' and ''Arctodus simus''), and Beringian wolves made up the megafaunal predator guild.<ref name="sciencedirect.com">{{Cite journal |last1=Mann |first1=Daniel H. |last2=Groves |first2=Pamela |last3=Kunz |first3=Michael L. |last4=Reanier |first4=Richard E. |last5=Gaglioti |first5=Benjamin V. |date=2013-06-15 |title=Ice-age megafauna in Arctic Alaska: extinction, invasion, survival |url=https://www.sciencedirect.com/science/article/pii/S0277379113001200 |journal=Quaternary Science Reviews |language=en |volume=70 |pages=91–108 |doi=10.1016/j.quascirev.2013.03.015 |bibcode=2013QSRv...70...91M |issn=0277-3791}}</ref><ref>{{Cite journal |last1=Monteath |first1=Alistair J. |last2=Gaglioti |first2=Benjamin V. |last3=Edwards |first3=Mary E. |last4=Froese |first4=Duane |date=2021-12-28 |title=Late Pleistocene shrub expansion preceded megafauna turnover and extinctions in eastern Beringia |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=52 |pages=e2107977118 |doi=10.1073/pnas.2107977118 |issn=0027-8424 |pmc=8719869 |pmid=34930836}}</ref> That caribou and [[muskox]] utilized the warmer, wetter portions of the regional vegetation mosaic (similar to the moist acidic tundra vegetation which dominates today), while horse, bison, and mammoth were dryland specialists,<ref name="sciencedirect.com"/> may reflect the preferred habitat of ''Arctodus'', as isotope data suggests caribou and muskox were principal components of the carnivorous portion of Beringian ''Arctodus simus''<nowiki/>' diet.<ref name=":312"/> Additionally, upon the flooding of the [[Bering Strait]] and [[Paludification|expansion]] of [[Mire|peatlands]] in Eastern Beringia during [[MIS 3|MIS-3]], [[Panthera spelaea|lions]], [[brown bear]]s and ''[[Homotherium]]'' went regionally extinct ~35,000 BP, whereas ''Arctodus'' persisted. Simultaneously, [[muskox]], [[bison]], non-caballine horses (''[[Haringtonhippus]]'') and other megafaunal herbivores in Beringia experienced population bottlenecks in MIS-3, whilst [[Woolly mammoth|mammoth]] populations steadily declined. This restriction of prey and habitat could explain the extinctions. However, genetically distinct ''[[Panthera spelaea]]'' and brown bears appear in [[MIS 2|MIS-2]] circa the extinction of ''Arctodus'' in a re-emerged Beringia ~23,000 BP (possibly due to sharp climatic cooling associated with [[Heinrich event|Heinrich Event-2]]), opening up the possibility that some level of competition was at play.<ref name=":19" /><ref name=":312"/><ref name=":422"/><ref name=":432"/> The idea that ''Arctodus'' had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|wolves]] and ''[[Homotherium]]'' in Beringia has been explored,<ref name=":312"/> and with the additional possibility that ''Arctodus'' restricted brown bears and ''Homotherium'' access to [[Reindeer|caribou]] pre-[[Last Glacial Maximum|LGM]].<ref name=":412">{{Cite journal |last1=Fox-Dobbs |first1=Kena |last2=Leonard |first2=Jennifer A. |last3=Koch |first3=Paul L. |date=2008-04-24 |title=Pleistocene megafauna from eastern Beringia: Paleoecological and paleoenvironmental interpretations of stable carbon and nitrogen isotope and radiocarbon records |url=https://www.sciencedirect.com/science/article/pii/S0031018208000266 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=261 |issue=1 |pages=30–46 |doi=10.1016/j.palaeo.2007.12.011 |bibcode=2008PPP...261...30F |issn=0031-0182}}</ref> Not only did ''Arctodus'' likely compete at a higher [[trophic level]] than the majority of brown bears in Beringia, ''Arctodus''<nowiki/>' [[Nitrogen 15|nitrogen-15]] levels are higher in the Yukon, suggesting that ''Arctodus'' possibly occupied an even higher trophic level there relative to other ''Arctodus'' in Beringia. However, isotope differences more likely reflect subtle differences in the isotopic composition of primary producers in the region.<ref name=":402"/><ref>{{Cite journal |last1=Lanoë |first1=François B. |last2=Reuther |first2=Joshua D. |last3=Holmes |first3=Charles E. |last4=Hodgins |first4=Gregory W. L. |date=2017-11-01 |title=Human paleoecological integration in subarctic eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0277379117300999 |journal=Quaternary Science Reviews |language=en |volume=175 |pages=85–96 |doi=10.1016/j.quascirev.2017.10.003 |bibcode=2017QSRv..175...85L |issn=0277-3791}}</ref> It would be reasonable to assume that meat and bone marrow were likely to be the primary food resources for some northern populations of ''A. simus'', in which the survival during the cold season could have depended on the regular scavenging of [[ungulate]] carcasses, as is the case with [[Kodiak bear|Alaskan brown bears]].<ref name="Figueiridio_et_al_20102"/> Ultimately, an opportunistic foraging strategy including up to 50% vegetation, and the meat of reindeer, muskox, [[carrion]], and possibly some predators, is consistent with the isotopic data and the conclusions of the ecomorphological studies.<ref name=":312"/> == Discussions regarding diet == === "Super predator" hypothesis === [[File:DSC09100_-_Extinct_Bear_(37221999825).jpg|thumb|Skeletal reconstruction of ''Arctodus simus''.]] One past proposal, suggested by [[Björn Kurtén]], envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed the [[megafauna]] of the Pleistocene with its great physical strength.<ref name=":162"/> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":212">{{Cite book |last=E. |first=Matheus, Paul |title=Locomotor adaptations and ecomorphology of short-faced bears (Arctodus simus) in eastern Beringia |date=2003 |publisher=Yukon Palaeontologist, Gov't. of Yukon |oclc=243520303}}</ref><ref name=":222">{{Cite book |last=Randally |first=Lynch, Eric |title=Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics |date=2012-08-06 |publisher=East Tennessee State University |oclc=818344518}}</ref> significantly more [[Gracility|gracile]] so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":202">{{Cite journal |last1=SOIBELZON |first1=LEOPOLDO H. |last2=SCHUBERT |first2=BLAINE W. |date=2011 |title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears |journal=Journal of Paleontology |volume=85 |issue=1 |pages=69–75 |doi=10.1666/10-037.1 |jstor=23019499 |s2cid=129585554}}</ref> Because its long legs may have enabled ''Arctodus'' to run at speeds of {{Convert|50|-|70|km/h|abbr=on|sigfig=1|mph}}, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref name=":212" /><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/> Additionally, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/> However, analysis of the forelimb of ''Arctodus'' suggests the bear could have been in the early stages of [[cursorial]] evolution- ''A. simus'' was somewhat more prone to [[Cursorial|cursorial tendencies]], being capable of more efficient locomotion, ''A. simus'' was interpreted as capable of high-speed (relative to extant bears), straight-line locomotion, and was likely more adept at pursuing large prey than the extant [[Polar bear|polar]] and [[brown bear]]s.<ref name=":222" /> However, that the limbs are elongated in the proximal rather than distal limb segments, had a plantigrade gait, and a stride which had little to no unsupported intervals, put doubt to this theory.<ref name=":132"/> Moreover, the pronation of the forearm and the flexion of the wrist and digits, and more lightly muscled forelimbs, all of which are crucial to grasping a large prey animal with the forepaws, were probably less powerful in ''Arctodus'' than in either the [[brown bear]] or in ''[[Panthera]].''<ref name=":110" /> Ultimately, the lack of specialized predatory adaptions (such as the absence of [[Canine tooth|laterally compressed canines]], and [[carnassial]]s built for crushing and grinding rather than shearing meat) puts doubt to any species-wide [[Hypercarnivore|hyper-carnivorous]] interpretations of ''Arctodus.''<ref name="Figueiridio_et_al_20102" /><ref name="Meloro 133–1462">{{Cite journal |last1=Meloro |first1=Carlo |last2=de Oliveira |first2=Alessandro Marques |date=2019-03-01 |title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf |journal=Journal of Mammalian Evolution |volume=26 |issue=1 |pages=133–146 |doi=10.1007/s10914-017-9413-x |s2cid=25839635}}</ref><ref name=":110" /> Although the only extant [[Hypercarnivore|hyper-carnivorous]] [[Bear|ursid]], the [[polar bear]], also lacks [[Carnassial|carnassial shears]], the species' primary subsistence on [[blubber]] rather than coarser flesh may negate the need to evolve dentition specialised in processing meat (the [[Polar bear|polar bear's]] recent evolution notwithstanding).<ref name=":132" /><ref name=":110" /> === Specialist kleptoparasite vs Omnivore === [[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|[[American mastodon]] arm bone with ''A.&nbsp;simus'' tooth marks at the [[Denver Museum of Nature & Science]] in [[Denver]], [[Colorado]]]] [[File:Shortfacedbear-1070375.jpg|thumb|226x226px|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of [[Molar (tooth)|molar]] damage associated with processing bone, [[Tooth decay|dental cavities]], and the lack of specialisation in the [[Canine tooth|canines]], discourages a [[Hypercarnivore|hyper-carnivorous]] interpretation of ''Arctodus''.]] ''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by paleontologist Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref> This idea was challenged by a comprehensive review by paleontologist Borja Figueirido and colleagues in 2010,<ref name="Figueiridio_et_al_20102" /> a 2013 study of the micro-wear of the teeth of various extant and extinct bears (examining ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]]), and a 2015 study focusing on [[carnivora]]ns recovered from [[Rancho La Brea]].<ref name="Donohue2">{{cite journal |author1=Donohue, Shelly L. |author2=DeSantis, Larisa R. G. |author3=Schubert, Blaine W. |author4=Ungar, Peter S. |year=2013 |title=Was the giant short-faced bear a hyper-scavenger? A new approach to the dietary study of ursids using dental microwear textures |journal=PLOS ONE |volume=8 |issue=10 |page=e77531 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name=":172">{{Cite journal |last1=DeSantis |first1=Larisa |last2=Schubert |first2=Blaine |last3=Schmitt-Linville |first3=Elizabeth |last4=Ungar |first4=Peter |last5=Donohue |first5=Shelly |last6=Haupt |first6=Ryan |date=2015-01-01 |title=Dental Microwear Textures of Carnivorans from the La Brea Tar Pits, California, and Potential Extinction Implications |url=https://www.researchgate.net/publication/282253545 |journal=La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas |pages=37–52}}</ref> Specialized scavengers like [[hyena]]s show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from [[La Brea Tar Pits|Rancho La Brea]], researchers concluded that ''Arctodus simus'' was not a specialized scavenger. Of living bears, this population of ''A. simus'' showed the most similar tooth wear patterns to its closest living relative, the [[spectacled bear]], which can have a highly varied diet- from obligate omnivory to, on the most part, being almost purely herbivorous in diet.<ref name=":132" /> However, this depends on the region, and seasonal availability.<ref name="Donohue2"/> Additionally, the higher rates of tooth breakage at La Brea were revisited, and due to a relative lack of bone related microwear on other carnivorans (even lower than the modern day) was attributed to the hunting of larger prey, and the acquisition and/or defense of kills.<ref name=":172" /> Moreover, severe tooth crown fractures and alveolar infections were found in the South American giant short faced bear ([[Arctotherium|''Arctotherium'' ''angustidens'']]). These were interpreted as evidence of feeding on tough materials (e.g. bones), which could tentatively indicate for these bears the regular scavenging of ungulate carcasses obtained through [[kleptoparasitism]]. However, such dental pathologies were not observed in the specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_20102" /> Additionally, the short, broad [[Rostrum (anatomy)|rostrum]] of ''Arctodus'' is a characteristic also shared with the [[sun bear]] and the [[spectacled bear]], which are both [[Omnivore|omnivorous]].<ref name="Figueiridio_et_al_20102" /> Moreover, isotope analyses of Beringian ''Arctodus'' specimens suggest that ''Arctodus'' had a low consumption rate of horses and mammoths in Beringia, despite those species making up ~50% of the available biomass in Beringia.<ref name=":312"/> Furthermore, the relative lack of ''Arctodus'' remains at [[predator trap]]s such as the [[La Brea Tar Pits|La Brea tar pits]], suggests that ''Arctodus'' did not compete for carcasses.<ref name=":142"/> Although [[La Brea Tar Pits|La Brea]] has produced more ''Arctodus simus'' specimens than any other site (presumably due to the quality of preservation with tar), they are only 1% of all carnivorans in the pits,<ref name=":172" /> which is a similar rate to [[brown bear]]s and [[American black bear|black bears]], both omnivorous [[Bear|ursids]] which lean towards herbivory.<ref>{{Cite journal |last1=McHorse |first1=Brianna K. |last2=Orcutt |first2=John D. |last3=Davis |first3=Edward B. |date=2012-04-15 |title=The carnivoran fauna of Rancho La Brea: Average or aberrant? |url=https://www.sciencedirect.com/science/article/pii/S0031018212000958 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=329-330 |pages=118–123 |doi=10.1016/j.palaeo.2012.02.022 |bibcode=2012PPP...329..118M |issn=0031-0182}}</ref> As only two specimens were located from the [[Natural Trap Cave]] in [[Wyoming]] by 1993, a similar rate (~0.9%) of relative abundance was calculated for ''Arctodus'' compared to other [[megafauna]] at the site.<ref>{{Cite journal |last1=Wang |first1=Xiaoming |last2=Martin |first2=Larry |date=1993-01-01 |title=Late Pleistocene, paleoecology and large mammal taphonomy, Natural Trap Cave, Wyoming |url=https://www.researchgate.net/publication/267156684 |journal=National Geographic Research & Exploration |volume=9 |pages=422–435}}</ref> Dental pathologies which have been found, such as [[incisor]] wear & [[Calculus (dental)|supragingival dental calculus]] in a young individual,<ref name=":210"/> and [[Tooth decay|cavities]] associated with [[carbohydrate]] consumption in individuals from [[La Brea Tar Pits|La Brea]], further suggest an omnivorous diet for ''Arctodus simus''.<ref name=":142" /> Further evidence comes from the evolution of brain size relative to body size- ursids which do not exhibit dormancy and have a high caloric diet, showed a weak but significant correlation with bigger relative brain size. ''Arctodus simus'' plotted in between the likely hypercarnivorous ''[[Cephalogale]],'' and the obligately herbivorous Eurasian cave bear and ''[[Indarctos]],'' suggesting omnivory.<ref>{{Cite journal |last=Veitschegger |first=Kristof |date=2017-06-05 |title=The effect of body size evolution and ecology on encephalization in cave bears and extant relatives |journal=BMC Evolutionary Biology |volume=17 |issue=1 |pages=124 |doi=10.1186/s12862-017-0976-1 |issn=1471-2148 |pmc=5460516 |pmid=28583080}}</ref> ==== Comparisons with modern fauna ==== [[File:Brown_bear_(Ursus_arctos_arctos)_running.jpg|thumb|Significant parallels can be found with the once contemporary [[brown bear]] (''Ursus arctos'') and [[hyena]]s.]] The most commonly accepted ecological parallels of ''Arctodus simus'' in scientific literature are the [[brown bear]] and the [[spectacled bear]].<ref name="Figueiridio_et_al_20102" /><ref name=":302"/><ref name=":156"/> Both being the most dominant [[carnivora]]ns of North America in the Late Pleistocene and Holocene respectively, both brown bears and ''Arctodus simus'' exhibit a high degree of dietary variability. Noting that [[Dietary biology of the brown bear|brown bears are largely herbivorous]], meat can be an important dietary element to certain populations. ''Arctodus'' follows a similar eco-morphology- while much evidence suggests herbivory, isotope data from some populations of ''Arctodus'' (such as those in [[Beringia]]) suggests the regular consumption of meat.<ref name=":312" /> Additionally, the potential of [[kleptoparasitism]] is often noted in ''Arctodus'', with brown bears being opportunistic, curious, and regularly steal kills from smaller predators.<ref name=":272"/><ref name=":312" /> Secondly, the spectacled bear (''Tremarctos ornatus''), the closest living relative of ''Arctodus'', is a herbivorous short-faced bear- both bears have been noted to share various adaptations for herbivory.<ref name="Figueiridio_et_al_20102" /> Another extant model for the eco-morphology of ''Arctodus'' may be the [[striped hyena]] and the [[brown hyena]]. ''Arctodus simus'' resembled these two living [[Hyena|hyaenids]], along with the predatory [[spotted hyena]], in skull shape and relative lengths of the trunk, back and limbs. The [[Striped hyena|striped]] and [[brown hyena]]s supplement their diet of large animal carrion and small animal prey with plant material in the form of [[fruit]], which can make up to half of the diet of some individuals of the [[brown hyena]] at certain times of the year.<ref name=":110" /> Another comparison can be made with the omnivorous [[maned wolf]] of [[South America]]. The [[maned wolf]] inhabits [[Grassland|open grassland]], has extremely long and slender limbs relative to body size (as has sometimes been interpreted in ''Arctodus simus''), is not especially fast, nor does it take swift prey, and runs with a loping gait. The long limbs may be an adaptation for increased vision over tall ground cover in an open habitat. However, it is equally possible that the longer limbs of ''Arctodus simus'' were used in tearing and pulling down vegetation, including [[shrub]]s and small trees, in order to feed on [[Leaf|leaves]], [[fruit]]s, [[Bark (botany)|bark]], [[seed]]s and [[flower]]s.<ref name=":132" /><ref name=":162"/> === Herbivory === [[File:Juniperus_communis_fruits_-_Keila.jpg|thumb|231x231px|Bear faeces found at [[The Mammoth Site]] in South Dakota containing [[Juniper berry|''Juniperus'' seeds]] likely belonged to ''Arctodus''. [[Conifer cone|Seed cones]] and [[Berry (botany)|berries]] are still an important food source for northern bears today.]] The fact that ''Arctodus'' did not significantly differ in dentition or build from modern bears has led most authors to support the hypothesis that the ''A. simus'' and the [[cave bear]] were omnivores, like most modern bears, and the former would have eaten plants depending on availability.<ref name="ScienceDaily2">ScienceDaily, 13&nbsp;April 2009.{{cite web |title=Prehistoric bears ate everything and anything, just like modern cousins |url=https://www.sciencedaily.com/releases/2009/04/090408170815.htm |access-date=2009-04-13 |website=ScienceDaily}}</ref> A 2006 study by Sorkin found dental and cranial adaptations for herbivory present in ''Arctodus simus'', suggest that the diet of the ''Arctodus'' included a large amount of plant material. Their cranial adaptations for increased bite force (including the short [[Rostrum (anatomy)|rostrum]]), broad [[Snout|muzzles]] (which would have precluded selective browsing), and the absence of digging adaptations in their forelimbs and claws (which would have limited [[Dietary biology of the brown bear#Plants and fungi|rooting]]) suggest that the plant material in their diet was coarse foliage, which was unselectively grazed.<ref name=":110" /> A 2008 study founds that the mandibular morphology of ''Arctodus simus'' noted that the similarity of ''Arctodus simus'' with the herbivorous ''Tremarctos ornatus'' is likely due to both a mandible shape which housed more primitive characteristics relative to other bears, and a convergence in dietary adaptations towards herbivory.<ref name=":82">{{Cite journal |last=Meloro |first=Carlo |date=2011-03-17 |title=Feeding habits of Plio-Pleistocene large carnivores as revealed by the mandibular geometry |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2011.550357 |journal=Journal of Vertebrate Paleontology |language=en |volume=31 |issue=2 |pages=428–446 |doi=10.1080/02724634.2011.550357 |s2cid=85255472 |issn=0272-4634}}</ref> Paleontologists Steven Emslie and Nicholas Czaplewski suggested that the body size of ''Arctodus simus'' exceeded the expected upper limitations for a [[Quaternary]] terrestrial carnivore (based on the more restrictive energy base for a carnivorous diet). This size discrepancy, along with a [[dentition]] akin to ''[[Spectacled bear|Tremarctos ornatus]]'', indicated a primarily herbivorous diet, but with the potential for opportunistic carnivory.<ref name=":132" /> This was challenged by a 1988 study, specifically on the basis of ''Arctodus''<nowiki/>' skull and body proportions being an impediment to foraging (especially in open areas), and the abundance of contemporary large prey. In particular, despite cranial adaptions strongly aligning with herbivory, a browsing diet foraged from the canopies of trees and shrubs could have been difficult with the large and flattened rostrum and incisor arcade of ''Arctodus''.<ref name=":162"/> However, again, due to the [[gracility]] and lack of agility of ''Arctodus'', ''Arctodus'' could probably neither prey upon adult [[Megafauna|mega-herbivores]],<ref name=":212" /><ref name=":222" /> nor actively chase down nimbler prey.<ref name="Simus2" /><ref name=":212" /> Additionally, studies of mandibular morphology and tooth microwear of bears confirms that short faced bears such as the spectacled bear and ''Arctodus'' were adapted to and actively consumed vegetation, whereas ''Ursus'' is omnivorous.<ref name=":302" /><ref name="Donohue2"/><ref name=":172" /><ref name=":82" /> Morphologically, ''Arctodus simus'' exhibits characteristics common to herbivorous bears. This includes cheek teeth with large surface areas, a deep mandible, and large mandibular muscle attachments (which are rare in carnivorous mammals). Because herbivorous carnivorans lack an efficient digestive tract for breaking down plant matter via microbial action, they must break down plant matter via extensive chewing or grinding, and thus possess features to create a high [[mechanical advantage]] of the jaw.<ref name=":132" /><ref name="Donohue2"/> While features of ''Arctodus simus'' morphology suggest herbivory, their close phylogenetic relationship to the omni-herbivorous [[spectacled bear]] presents the possibility that these traits may be an ancestral condition of the group. Regardless, gross tooth wear suggests consumption of at least some plant matter in the diet of ''Arctodus simus'' at [[La Brea Tar Pits|La Brea]]''.'' Despite presumed variety in the diet of ''Arctodus simus'', the diet of individuals from [[La Brea Tar Pits|La Brea]] were likely less generalized than modern [[American black bear|black bear]], based on the consistency of ''Arctodus''<nowiki/>' tooth wear.<ref name="Donohue2"/> Fossils of bear [[coprolite]]s found in association with ''Arctodus'' remains at [[The Mammoth Site]] in [[South Dakota]] are believed to contain [[Juniper|''Juniperus'']] seeds.<ref name=":292" /> === Opportunistic carnivory === [[File:American_mastodon_with_calf.jpg|thumb|''Arctodus'' may have found young [[proboscidea]]ns to be suitable prey.|left]] Although evidence suggests that ''Arctodus'' also consumed meat, studies suggest that isotope data cannot differentiate between hypercarnivores and omnivores which consume significant amounts of animal matter.<ref name=":110" /> The bite marks found on many bones of ground sloths (''[[Nothrotheriops|Northrotheriops texanus]]'') and young [[proboscidea]]ns at [[Cockroach Bay Aquatic Preserve|Leisey Shell Pit]] in [[Florida]] matched the size of the canine teeth of ''Arctodus pristinus''. It is not known if these bite marks are the result of active predation or scavenging.<ref name=":262"/> Evidence from the [[Δ13C|carbon isotope]] values of an ''Arctodus simus'' individual from [[Cedral, San Luis Potosí|Cedral]], [[San Luis Potosí]], [[Mexico|México]], suggested that ''Arctodus simus'' from this locality preferred areas of closed vegetation. Owing to having only one sample of ''Arctodus simus'' from [[Cedral, San Luis Potosí|Cedral]] and the lack of nitrogen isotopic values, the study found it difficult to infer whether ''Arctodus simus'' was an [[omnivore]] or [[hypercarnivore]]. The [[Δ13C|''δ''<sup>13</sup>C]] value, however, showed that this individual fed upon [[C3 carbon fixation|C3]] resources- in fact, that ''Arctodus'' individual had the strongest [[Δ13C|''δ''<sup>13</sup>C]] value of the fauna studied. ''Arctodus''<nowiki/>' [[Carbon-13|carbon isotope]] value did not overlap with, but was closest to values from the [[tapir]] and ''[[Hemiauchenia]]''. Those animals could have been included in their diet, along with other contemporaneous [[C3 carbon fixation|C3]] herbivores such as [[Camelops|camels]], [[Platygonus|peccaries]], [[Nothrotheriops|Shasta ground sloth]] and [[mastodon]], along with C3 vegetation.<ref name=":410"/> [[File:Smilodon_gaping.jpg|thumb|The enormous canines of sabertooth cats such as ''[[Smilodon]]'' would have made carcass consumption difficult, presenting a scavenging opportunity for ''Arctodus''.]] A likely faunal interaction was between ''[[Smilodon]]'' and ''Arctodus''- the sabretooth cat's theorized inability to consume all but the soft tissue of their kills would leave large portions of the carcass available to scavengers such as ''Arctodus''. ''Arctodus''<nowiki/>' scavenging had the potential to be [[Kleptoparasitism|kleptoparasitic]]- however, in addition to many contemporaneous predators being [[Sociality|gregarious]] and thus better able to defend their kills, ''Arctodus''<nowiki/>' great size variation would have likely limited the frequency of this behavior to all but the largest ''Arctodus simus''.<ref name="Figueiridio_et_al_20102" /> For specimens from inland [[California]] ([[Madera County, California|Fairmead Landfill]]) from the [[Irvingtonian|Middle Pleistocene]], a 2012 study proposed that ''Arctodus simus'' consumed Colombian mammoth, and large [[ungulate]]s- that ''Arctodus'' likely consumed substantial amounts of vegetation made conclusive determinations unclear.<ref name=":72">{{Cite journal |last=Trayler |first=Robin Brendan |date=December 2012 |title=Stable Isotope Records of Inland California Megafauna- New Insights Into Pleistocene Paleoecology and Paleoenvironmental Conditions (Masters Thesis) |url=https://scholarworks.calstate.edu/downloads/h128nf901 |journal=College of Science and Mathematics, California State University Fresno}}</ref> However, the author republished in 2015 with colleagues, recalibrating ''Arctodus''<nowiki/>' [[Δ13C|''δ''<sup>13</sup>C]] values to be closest to [[C3 carbon fixation|C3 vegetation]] consuming ''[[Cervus]]'' and ''[[Mastodon|Mammut]]'', if the consumption of C3 vegetation by ''Arctodus'' is not included.<ref name=":232"/> In the later Californian [[McKittrick Tar Pits]], ''Arctodus simus'' had a diet which included [[deer]] and [[tapir]], similar to the one inferred for the [[Cedral, San Luis Potosí|Cedral]] individual.<ref name=":410" /> [[Alaska]]n specimens were thought to also largely predate upon similar megafauna as proposed for the Fairmead individuals in the 2012 study,<ref name=":272"/> but isotope data suggests [[reindeer]], [[muskox]] and possibly fellow predators and their kills, were regularly consumed.<ref name=":312" /> A single find from the [[Channel Islands (California)|Channel Islands]] of [[California]] replete with nitrogen isotope signatures aligning with [[bison]] and [[Camelidae|camels]] (followed by [[pinniped|seal]]s) bolsters the suggestion that although not entirely carnivorous, ''A. simus'' would have had a flexible diet across its range. That the ''Arctodus'' fossil in the [[Channel Islands (California)|Channel Islands]] was likely transported post-mortem from the [[California|North American mainland]] further complicates the idea of a standard diet for ''Arctodus,'' as the mainland would have had plenty of vegetation to consume. However, the partial reliance on marine resources has been suggested to be as a result of a competitive megafaunal carnivore guild- the marine signal was in between [[island fox]]es and [[bald eagle]]s, most closely resembling Late Pleistocene [[California condor]]s.<ref name=":47"/> Bone damage on a [[Cranium|cranial fragment]] (and possibly the humerus) of an ''Arctodus'' individual in a cave on [[Vancouver Island]] has been attributed to another ''Arctodus'', on the basis that ''Arctodus'' was the only confirmed large terrestrial [[carnivora]]n at the locality.<ref name=":156"/> ''Arctodus'' has been found in association with [[proboscidea]]n remains near [[Frankstown Township, Blair County, Pennsylvania|Frankstown]], [[Pennsylvania]] (juvenile [[mastodon]]), and at [[The Mammoth Site]], [[South Dakota]] ([[Columbian mammoth]]s). However, questions remain as to whether these finds determine a predatory or scavenging relationship, or whether they were simply preserved at the same deposit.<ref name=":292" /><ref>{{Cite web |date=2010-02-17 |title=A Baby Mastodon Deathtrap (?) |url=https://www.nationalgeographic.com/science/article/a-baby-mastodon-deathtrap |access-date=2022-06-09 |website=Science |language=en}}</ref> On the other hand, a [[woolly mammoth]] specimen from [[Saltville, Virginia|Saltville]], [[Virginia]] was likely scavenged on by ''Arctodus simus'', as evidenced by a [[Canine tooth|canine]] gouge through the [[calcaneus]].<ref name=":332" /> Several Columbian mammoth bones from a cave near [[Sanpete County, Utah|Huntington Reservoir]], [[Utah]] also record ursid gnaw marks attributed to ''Arctodus'', with an ''Arctodus'' specimen preserved in association with the remains.<ref name=":382"/> A [[mastodon]] [[humerus]] from the [[Snowmastodon site]] in [[Colorado]] bears tooth marks also suggested to be from ''Arctodus''.{{Citation needed|date=June 2022}} Importantly, the canines of ''[[American lion|Panthera atrox]]'' overlap in size with ''Arctodus simus'', complicating the identification of tooth marks.<ref name=":332" /> However, this is not to discredit all tooth marks attributed to ''Arctodus'', as damaged bones from an ''Arctodus'' den site in Alaska suggest that ''Arctodus'' transported megafaunal [[Long bone|longbones]] back to a cave-like den and chewed on them,<ref>{{Cite journal |last=Sattler |first=Robert A. |date=1997 |title=Large Mammals in Lower Rampart Cave 1, Alaska: Interspecific Utilization of an Eastern Beringian Cave |journal=Geoarchaeology|volume=12 |issue=6 |pages=657–688|doi=10.1002/(SICI)1520-6548(199709)12:6<657::AID-GEA7>3.0.CO;2-Y }}</ref> at a time when lions had a limited overlap with ''Arctodus'' in Beringia.<ref name=":19" /><ref name=":142" /> Furthermore, a perforated [[Platygonus compressus|peccary]] ilium from [[Sheriden Cave]] has also been hypothesised as being scavenged by ''Arctodus simus''.<ref name=":322"/> [[File:SpectacledBear1_CincinnatiZoo.jpg|thumb|222x222px|''Arctodus''<nowiki/>' closest extant relative, the [[spectacled bear]], could provide a behavioural analogue for their extinct [[Tremarctinae|tremarctine]] relatives.]] Endemic to the [[Andes|South American highlands]], the last surviving [[Tremarctinae|short-faced bear]] is the [[spectacled bear]]. Although mostly herbivorous, the modern [[spectacled bear]] is on occasion an active predator. The [[spectacled bear]] has several hunting techniques- principally, the bear surprises or overpowers its prey, mounts its back, and consumes the immobilized animal while still alive, pinning the prey with its weight, large paws and long claws. Alternatively, the bear pursues the prey into rough terrain, hillsides, or precipices, provoking its fall and/or death. After death, the prey is dragged to a safe place (e.g. a forested area) and consumed, leaving only skeletal remains.<ref>{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Grinspan |first2=Gustavo A. |last3=Bocherens |first3=Hervé |last4=Acosta |first4=Walter G. |last5=Jones |first5=Washington |last6=Blanco |first6=Ernesto R. |last7=Prevosti |first7=Francisco |date=November 2014 |title=South American giant short-faced bear (Arctotherium angustidens) diet: evidence from pathology, morphology, stable isotopes, and biomechanics |url=http://naturalis.fcnym.unlp.edu.ar/repositorio/_documentos/sipcyt/bfa004877.pdf |journal=Journal of Paleontology |volume=88 |issue=6 |pages=1240–1250 |doi=10.1666/13-143 |s2cid=54869873}}</ref> These behaviors may be applicable to the giant short-faced bears ''[[Arctotherium]]'' and ''Arctodus''. ==== Beringia ==== Analysis of bones from [[Alaska]] showed high concentrations of [[Isotopes of nitrogen#Nitrogen-15|nitrogen-15]], a stable nitrogen isotope accumulated by carnivores. Additionally, although few specimens exist, there is currently no evidence of the same carbohydrate-related [[Tooth decay|dental pathologies]] evident in southern populations of ''Arctodus simus''.<ref name=":142" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more [[Carnivore|carnivorous]] in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C3 vegetation]], particularly [[Reindeer|caribou]]).<ref name=":312" /><ref name=":412"/> A 2015 study suggests that caribou could not account for the high levels of [[Δ13C|carbon-13]] and [[Nitrogen 15|nitrogen-15]] in some ''Arctodus'' individuals in Beringia. The study suggests that the consumption of [[Muskox|tundra muskox]], which sometimes express high proportions of these isotopes, and possibly other predators in its Beringian range, may explain the data.<ref name=":312" /> Increased carnivory may be due to a lower proportion of competitors and probably a lower availability of carbohydrate-rich food supplies across the year in the far northern latitudes.<ref name=":142" /> Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, the average (700&nbsp;kg) [[Beringia]]n ''Arctodus'' individual needed to consume ~5853&nbsp;kg of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain 100&nbsp;kg of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref> Studies point out that ''A. simus'' would have had a varied diet across its range,<ref name="Donohue2"/> and that the features of the skull and teeth match modern omnivorous bears. Additionally, the isotope data purportedly establishing the carnivory of Beringian ''Arctodus'' overlapped with modern, [[Dietary biology of the brown bear|omni-herbivorous]] brown bears from [[Europe]], eastern [[Wyoming]], and central [[Montana]], demonstrating that isotope data cannot distinguish between [[hypercarnivore]]s and [[omnivore]]s which eat a significant amount of animal matter.<ref name=":110" /> However, this has been challenged on the basis that herbivory should be more obvious in the data gathered from ''Arctodus''.<ref name=":332" /> Regardless, the local extinction of ''Arctodus'' in [[Beringia]] ~23,000 BP,<ref name=":19" /><ref name=":156"/> much earlier than in other parts of its range, raises questions about how suited ''Arctodus'' was to a hypothetically [[Hypercarnivore|carnivorous]] niche, and why, whilst recolonized by [[Panthera spelaea|cave lions]] and [[brown bear]]s, ''Arctodus'' didn't repopulate [[Beringia]] once the ice-free corridor to the south re-opened later in the [[Pleistocene]].<ref name=":19" /><ref name=":182">{{Cite journal |last1=Pedersen |first1=Mikkel W. |last2=Ruter |first2=Anthony |last3=Schweger |first3=Charles |last4=Friebe |first4=Harvey |last5=Staff |first5=Richard A. |last6=Kjeldsen |first6=Kristian K. |last7=Mendoza |first7=Marie L. Z. |last8=Beaudoin |first8=Alwynne B. |last9=Zutter |first9=Cynthia |last10=Larsen |first10=Nicolaj K. |last11=Potter |first11=Ben A. |date=2016 |title=Postglacial viability and colonization in North America's ice-free corridor |url=http://eprints.gla.ac.uk/138297/1/138297.pdf |journal=Nature |volume=537 |issue=7618 |pages=45–49 |bibcode=2016Natur.537...45P |doi=10.1038/nature19085 |pmid=27509852 |s2cid=4450936}}</ref> == Human interaction == [[File:Clovis Point.jpg|thumb|The [[Clovis culture|Clovis people]] are the first known culture to have interacted with ''Arctodus''.|left]]One documented interaction with [[Clovis culture|Clovis people]] is present at the [[Lubbock Lake Landmark]], [[Texas]]. A likely already deceased ''Arctodus simus'' was processed for subsistence (butchery marks indicated skinning, de-fleshing and disarticulation) and technology (raw material resource for tool production), much in the same way as a [[Columbian mammoth|mammoth carcass]] (~13,000 BP / 11,100 [[Carbon-14|<sup>14</sup>C]] BP ).<ref name=":112"/> Additionally, other remains of the ''Arctodus simus'' have been found in association with [[Paleo-Indians|Paleo-Indian]] artifacts in [[Sheriden Cave]], [[Wyandot County, Ohio|Ohio]],<ref name=":282"/><ref name=":322"/><ref name="Redmond2">{{cite web |author=Brian G. Redmond |date=March 2006 |title=Before the Western Reserve: An Archaeological History of Northeast Ohio |url=https://www.cmnh.org/CMNH/media/CMNH_Media/C-R%20Docs/BeforeWR.pdf |access-date=January 28, 2020 |publisher=The Cleveland Museum of Natural History |page=2}}</ref> and Huntington Dam, Utah.<ref name=":382"/> It is clear that people were at least occasionally involved in the death and/or butchery of several different large non-carnivorous Pleistocene mammals, particularly [[mammoth]]s and [[mastodon]]s. This may at times have put people in competition with ''Arctodus simus'' for carcasses, and possibly for prey. Defense against these large bears as well as abandonment of carcasses are plausible outcomes. The relationship between people and ''Arctodus simus'' is likely to have been uneasy at best.<ref name=":156"/> === Migration barrier hypothesis === [[Valerius Geist|Val Geist]] once hypothesized that humans moving into [[North America]] may have found large Pleistocene carnivores such as ''Arctodus simus'' to be a barrier to gaining a foothold.<ref name=":272"/> [[Beringia]]n forms of ''Arctodus'' were the largest and most powerful carnivorous land mammals in North America, with the potential specialization in obtaining and dominating distant and scarce resources. Humans in this hypothesis, though familiar with [[brown bear]]s, would not have been able to effectively contend with the ''Arctodus simus'' and other large Pleistocene carnivores, a situation that would have suppressed human population expansion. However, this has been discredited by modern research- evidence continues to maintain a prolonged co-existence of humans and ''Arctodus'' across North America. ==== Beringia ==== [[File:Ccsm4_beringia_lgm_tundratypes_by_temperature_1.png|thumb|313x313px|[[Beringia]] during the [[Last Glacial Maximum]].]] Humans migrated to North America via the Siberian [[mammoth steppe]], arriving at [[Beringia|Eastern Beringia]] (Alaska and the Yukon). However, the migration was halted at the [[Wisconsin glaciation|North American Ice Sheet]], which separated Beringia and southern North America for most of the Late Pleistocene.<ref>{{Cite journal |last1=Graf |first1=Kelly E. |last2=Buvit |first2=Ian |date=2017-12-01 |title=Human Dispersal from Siberia to Beringia: Assessing a Beringian Standstill in Light of the Archaeological Evidence |url=https://www.journals.uchicago.edu/doi/full/10.1086/693388 |journal=Current Anthropology |volume=58 |issue=S17 |pages=S583–S603 |doi=10.1086/693388 |issn=0011-3204 |s2cid=149080106}}</ref> Both humans and ''Arctodus'' are first dated to ~50,000 BP in Beringia, both from sites in the Yukon, and co-existed until ''Arctodus'' went extinct in Beringia ~23,000 BP during the [[Last Glacial Maximum]]. This co-existence was despite the regional extinction of other Beringian predators such as [[Panthera spelaea|lions]], brown bears and [[Homotherium|saber-tooth cats]]. Important sites of pre-LGM human occupation in Beringia include the [[Old Crow Flats]], [[Kuparuk River|Kuparuk River Valley]] & the [[Bluefish Caves]].<ref>{{Cite journal |last1=Holen |first1=Steven R. |last2=Harington |first2=C. Richard |last3=Holen |first3=Kathleen A. |date=2017 |title=New Radiocarbon Ages on Percussion-Fractured and Flaked Proboscidean Limb Bones from Yukon, Canada |url=https://www.jstor.org/stable/26379757 |journal=Arctic |volume=70 |issue=2 |pages=141–150 |doi=10.14430/arctic4645 |jstor=26379757 |issn=0004-0843}}</ref><ref>{{Cite journal |last1=Bourgeon |first1=Lauriane |last2=Burke |first2=Ariane |last3=Higham |first3=Thomas |date=2017-01-06 |title=Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada |journal=PLOS ONE |language=en |volume=12 |issue=1 |pages=e0169486 |doi=10.1371/journal.pone.0169486 |issn=1932-6203 |pmc=5218561 |pmid=28060931|bibcode=2017PLoSO..1269486B |doi-access=free }}</ref><ref>{{Cite journal |last=Bourgeon |first=Lauriane |date=2021-06-01 |title=Revisiting the mammoth bone modifications from Bluefish Caves (YT, Canada) |url=https://www.sciencedirect.com/science/article/pii/S2352409X21001814 |journal=Journal of Archaeological Science: Reports |language=en |volume=37 |pages=102969 |doi=10.1016/j.jasrep.2021.102969 |s2cid=234816694 |issn=2352-409X}}</ref><ref>{{Cite journal |last1=Goebel |first1=Ted |last2=Hoffecker |first2=John F. |last3=Graf |first3=Kelly E. |last4=Vachula |first4=Richard S. |date=June 2022 |title=Archaeological reconnaissance at Lake E5 in the Brooks Range, Alaska and implications for the early human biomarker record of Beringia |url=https://linkinghub.elsevier.com/retrieve/pii/S0277379122001846 |journal=Quaternary Science Reviews |language=en |volume=286 |pages=107553 |doi=10.1016/j.quascirev.2022.107553|bibcode=2022QSRv..28607553G |s2cid=248736952 }}</ref> ==== Contiguous North America ==== Additionally, the human colonization of North America south of the ice sheets further disproves the idea that ''Arctodus'' was a migration barrier. Pre-[[Last Glacial Maximum|LGM]] sites across the Americas such [[Chiquihuite cave|Chiquihuite Cave]], [[Hueyatlaco|Valsequillo]],<ref>{{Cite journal |last=Pichardo |first=M. |date=1997 |title=Valsequillo biostratigraphy: New evidence for Pre-Clovis date |url=https://www.jstor.org/stable/29540729 |journal=Anthropologischer Anzeiger |volume=55 |issue=3/4 |pages=233–246 |doi=10.1127/anthranz/55/1997/233 |jstor=29540729 |issn=0003-5548}}</ref> El Cedral,<ref>{{Cite journal |last1=Gonzalez |first1=Sofia |last2=Huddart |first2=David |date=2008 |title=The Late Pleistocene Human Occupation of Mexico |url=https://www.researchgate.net/publication/265490787 |journal=FUMDHAMentos VII |via=ResearchGate}}</ref> [[Calico Early Man Site|Calico]], [[Pendejo Cave]] and [[White Sands National Park|White Sands]] suggest that humans co-existed with ''Arctodus'' for many thousands, if not tens of thousands of years. This extensive overlap with ''Arctodus'' across [[North America]] puts significant doubt to the migration barrier hypothesis. The earliest universally accepted post LGM/pre-[[Clovis culture|Clovis]] site is [[Monte Verde]] in Chile, dated to ~15,000 BP. Similarly dated sites from [[Saltville (archaeological site)|Saltville]], La Sena, [[Meadowcroft Rockshelter|Meadowcroft]], [[Topper Site|Topper]], [[Triquet Island]], [[Cactus Hill]], and [[Buttermilk Creek (Texas)|Buttermilk Creek]] in the USA further solidify a rapid human expansion across the Americas.<ref name=":156"/> There is no evidence that ''Arctodus'', or other Pleistocene carnivores below the [[Laurentide Ice Sheet]] were in any way an impediment to the peopling of the Americas. == Extinction == [[File:Arctodus simus skeletal.jpg|thumb|Skeletal reconstruction of ''Arctodus simus''.]]''Arctodus simus'' went extinct around 12,000 years ago, which was relatively late when compared to other victims of the [[Quaternary extinction|Quaternary extinction event]].<ref>{{Cite journal |last1=Faith |first1=J. Tyler |last2=Surovell |first2=Todd A. |date=2009-12-08 |title=Synchronous extinction of North America's Pleistocene mammals |journal=Proceedings of the National Academy of Sciences |volume=106 |issue=49 |pages=20641–20645 |doi=10.1073/pnas.0908153106 |issn=0027-8424 |pmc=2791611 |pmid=19934040 |bibcode=2009PNAS..10620641F |doi-access=free}}</ref> ''Arctodus'' was also one of the last (16 out of 35) North American megafauna to go extinct, having reached the Pleistocene-Holocene boundary (13,800 BP - 11,400 BP).<ref name=":442"/> Various factors, including the depletion in number of large herbivores,<ref name=":34" /> the diminishing nutritional quality of plants during climate change, and competition with fellow omnivores ([[Paleo-Indians|humans]] and [[brown bear]]s) for food resources, have been suggested as the cause of ''Arctodus simus''<nowiki/>' extinction.<ref name=":112"/> However, multiple studies put doubt on brown bears being culpable in ''Arctodus simus''<nowiki/>' extinction.<ref name=":92"/><ref name=":156"/><ref name=":162"/> Moreover, there is no strong evidence that humans hunted large extinct Pleistocene carnivores in North America, and no clear indication of direct human involvement in the extinction of ''Arctodus simus''.<ref name=":156"/> Additionally, no evidence from [[La Brea Tar Pits|Rancho La Brea]] suggests that food shortages were to blame for the demise of ''Arctodus simus'', or other large bodied [[carnivora]]ns.<ref name="Donohue2"/> Of these factors, vegetation shifts in the latest Pleistocene may have been particularly unfavorable for ''Arctodus simus,'' due to a reduction of quality foraging for subsistence. For example, on [[Vancouver Island]] (∼13,500 BP), vegetation changed rapidly from open [[woodland]]s with abundant [[Pinus contorta|lodgepole pine]] to increasingly closed forests with shade-tolerant [[Picea|spruce]], [[Tsuga mertensiana|mountain hemlock]], and [[Alnus rubra|red alder]]. These changes, effective by ∼12,450 BP, point toward cool and moist conditions during the [[Younger Dryas|Younger Dryas stadial]]. Closed forests continued to expand in the [[Greenlandian|early Holocene]], with [[Tsuga heterophylla|western hemlock]] becoming dominant. Even though ''Arctodus simus'' was not restricted to open areas and could occur in different environments, the timing of the regional shift from an open pine [[woodland]] habitat to a densely forested vegetation implies that these vegetation changes contributed to the local extirpation of ''Arctodus simus'', along with many other megafauna.<ref name=":156"/> Loss and turnover of the diversity of mitochondrial DNA before the Last Glacial Maximum has been noted amongst Eurasian and American megafauna such as bison, lions, horses and mammoths. This is predicated by a decrease in population size from a previously genetically diverse population in the Late Pleistocene, followed by either a repopulation from a source population, or extinction at the start of the Holocene. Correspondingly, ''Arctodus simus'' had a very low level of genetic diversity from most sampled specimens, albeit a sample with a Beringian and temporal bias (<44,000 BP). A reduced ability to adapt to environmental conditions has been attributed to a lack of genetic diversity, and this combination has contributed to the endangerment of modern specialized carnivores such as lions and Tasmanian devils. That the individual from Sheriden Cave, Ohio was very closely related to Beringian specimens further may support this idea, as these populations had possibly been isolated from before the Last Glacial Maximum (tens of thousands of years).<ref name=":49" /> A similar level of genetic affinity between Beringian fauna and some southern populations has been found in contemporary camels and horses.<ref>{{Cite journal |last1=Mitchell |first1=Kieren J. |last2=Bover |first2=Pere |last3=Salis |first3=Alexander T. |last4=Mudge |first4=Caitlin |last5=Heiniger |first5=Holly |last6=Thompson |first6=Mary |last7=Hockett |first7=Bryan |last8=Weyrich |first8=Laura S. |last9=Cooper |first9=Alan |last10=Meachen |first10=Julie A. |date=November 2021 |title=Evidence for Pleistocene gene flow through the ice-free corridor from extinct horses and camels from Natural Trap Cave, Wyoming |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618221005589 |journal=Quaternary International |language=en |pages=S1040618221005589 |doi=10.1016/j.quaint.2021.11.017|s2cid=244706923 }}</ref> Small population sizes may also be characteristic of tremarctine bears- the spectacled bear, while having low levels of genetic diversity, has no signs of a recent genetic bottleneck. However, brown bears, along with many recently immigrated taxa, had diverse, [[Sympatry|sympatric]] source populations in Eurasia, allowing for repopulations/reinvasions into the Americas. If ''Arctodus simus'' experienced genetic bottlenecks or local extinctions prior to the Last Glacial Maximum, ''Arctodus'' would have been unable to supplement their reduced genetic diversity with new migrants like the brown bear could, making them vulnerable to extinction.<ref name=":49" /> The youngest date for ''Arctodus simus'' is circa 12,700 BP from [[San Antonio|Friesenhahn Cave]], [[Texas]], calibrated from 10,814 ± 55 [[radiocarbon year]]s ([[Carbon-14|<sup>14</sup>C]] BP). However, this date should be viewed with caution, as analyses suggest the collagen protein was degraded. A vertebra from [[Bonner Springs, Kansas|Bonner Springs]], [[Kansas]], was dated to ca. 12,800 BP (based on 10,921 ± 50 radiocarbon years) from well preserved collagen. However, another radiocarbon date from a different laboratory on the same vertebra widens the possible age of the vertebra to between 9,510 and 11,021 <sup>14</sup>C BP (at 2''σ''). Nevertheless, a specimen from [[Huntington North Dam|Huntington Dam]], [[Utah]] was also dated to ca. 12,800 BP from two radiocarbon dates (10,870 ± 75 & 10,976 ± 40 <sup>14</sup>C BP) and is therefore considered reliable.<ref name=":122" /><ref name=":442" /> == Directly sampled specimens == === Radiocarbon dated specimens === Below is a table collating [[Radiocarbon dating|radiocarbon dates]] directly sampled from ''Arctodus simus'' specimens (not including dates from associated remains nor stratigraphy).<ref name="Pedersen 2728–2736.e8" /><ref name=":24" /><ref name=":49" /><ref name=":12" /><ref name=":272"/><ref name=":156"/><ref name="sciencedirect.com" /><ref name=":47">{{Cite journal |last1=Mychajliw |first1=Alexis M. |last2=Rick |first2=Torben C. |last3=Dagtas |first3=Nihan D. |last4=Erlandson |first4=Jon M. |last5=Culleton |first5=Brendan J. |last6=Kennett |first6=Douglas J. |last7=Buckley |first7=Michael |last8=Hofman |first8=Courtney A. |date=2020-09-16 |title=Biogeographic problem-solving reveals the Late Pleistocene translocation of a short-faced bear to the California Channel Islands |journal=Scientific Reports |volume=10 |issue=1 |pages=15172 |doi=10.1038/s41598-020-71572-z |pmc=7494929 |pmid=32938967}}</ref><ref name=":44">{{Cite journal |last=Stuart |first=Anthony John |date=May 2015 |title=Late Quaternary megafaunal extinctions on the continents: a short review: LATE QUATERNARY MEGAFAUNAL EXTINCTIONS |url=https://onlinelibrary.wiley.com/doi/10.1002/gj.2633 |journal=Geological Journal |language=en |volume=50 |issue=3 |pages=338–363 |doi=10.1002/gj.2633 |s2cid=128868400}}</ref><ref name=":45">{{Cite journal |last1=Fox-Dobbs |first1=Kena |last2=Dundas |first2=Robert. G. |last3=Trayler |first3=Robin B. |last4=Holroyd |first4=Patricia A. |date=January 2014 |title=Paleoecological implications of new megafaunal 14 C ages from the McKittrick tar seeps, California |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2013.791694 |journal=Journal of Vertebrate Paleontology |language=en |volume=34 |issue=1 |pages=220–223 |doi=10.1080/02724634.2013.791694 |issn=0272-4634 |s2cid=128943450}}</ref><ref>{{Cite journal |last1=O'Keefe |first1=F. Robin |last2=Fet |first2=Elizabeth V. |last3=Harris |first3=John M. |date=2009-12-04 |title=Compilation, calibration, and synthesis of faunal and floral radiocarbon dates, Rancho La Brea, California |url=https://www.biodiversitylibrary.org/part/226783 |journal=Contributions in Science |volume=518 |pages=1––16 |doi=10.5962/p.226783 |s2cid=128107590 |issn=0459-8113}}</ref><ref>{{Cite journal |last1=Mann |first1=Daniel H. |last2=Groves |first2=Pamela |last3=Reanier |first3=Richard E. |last4=Gaglioti |first4=Benjamin V. |last5=Kunz |first5=Michael L. |last6=Shapiro |first6=Beth |date=2015-11-17 |title=Life and extinction of megafauna in the ice-age Arctic |journal=Proceedings of the National Academy of Sciences |language=en |volume=112 |issue=46 |pages=14301–14306 |doi=10.1073/pnas.1516573112 |issn=0027-8424 |pmc=4655518 |pmid=26578776|bibcode=2015PNAS..11214301M |doi-access=free }}</ref><ref>{{Cite journal |last=Storer |first=J. |date=2003 |editor-last=Froese |editor-first=D.G. |editor2-last=Zazula |editor2-first=G. D. |title=Vertebrate Palaeontology of the Klondike Area |url=https://emrlibrary.gov.yk.ca/Tourism/international-mammoth-conference-third-field-guide-2003.pdf |journal=3rd International Mammoth Conference Field Guide to Quaternary Research in the Klondike Goldfields |volume=Occasional Papers in Earth Sciences No. 6 |pages=24–29 |via=Palaeontology Program, Government of the Yukon}}</ref><ref name=":11" /> {| class="wikitable sortable" |+ !Location !Element & ID !<sup>14</sup>C Date (1''σ'') !<sup>14</sup>C Range (2''σ)'' !Calibrated dates |- |[[San Antonio|Friesenhahn Cave]], [[Texas]] |[[Wisdom tooth|M3]] [[Molar (tooth)|molar]] [[dentin]]e (TMM 933–2205) |10,814 ± 55 BP |10,704–10,924 BP |12,700 BP |- |[[Bonner Springs, Kansas|Bonner Springs]] ([[Kansas River|Kansas River/ Kaw River Bank]]), [[Kansas]] |[[Lumbar vertebrae|Lumbar vertebra]] (KUVP 81230) ~ [[Femur]] (KUVP 131586) |9630 ± 60 BP 10,921 ± 50 BP¹ 11,688 ± 50 BP |N/A 10,821–11,021 BP¹ 11,588–11,788 BP |12,800 BP¹ |- |[[Sanpete County, Utah|Huntington Dam]], [[Utah]] |[[Maxilla]] (UMNH VP 9510) |10,870 ± 75 BP 10,976 ± 40 BP |~ 10,896–11,056 BP |12,800 BP |- |[[McKittrick Tar Pits|McKittrick Tar Seeps]], [[California]] |[[Ulna]] (UCMP 153245) |11,040 ± 310 BP |N/A |N/A |- |[[Fulton County, Indiana|Fulton County]], [[Indiana]] |[[Rib]] |11,500 ± 520 BP* |N/A |N/A |- |[[Sheriden Cave]], [[Ohio]] |[[Carpal bones|Scapholunar]] (CMNH 2001) ~ ~ [[Talus bone|Astragalus]] ~ |11,480 ± 60 BP 11,566 ± 40 BP¹ 11,570 ± 50 BP 11,570 ± 70 BP 11,610 ± 90 BP |11,486–11,646 BP¹ |N/A |- |[[Nimpkish Lake|Pellucidar Cave]], [[Vancouver Island]] |[[Palatine bone|Palatine]] (PC2–1c) M2 molar dentine (PC2–1a) [[Humerus]] (PC2-3) |11,615 ± 30 BP 11,720 ± 50 BP 11,775 ± 30 BP |N/A |13,379–13,557 BP 13,477–13,725 BP 13,575–13,964 BP |- |[[Salt Lake Valley]] ([[Lake Bonneville|Bonneville]]), [[Utah]] |Femur (UVP 015/1) |12,650 ± 70 BP* |N/A |N/A |- |[[San Miguel Island]] (Daisy Cave), California |[[Metacarpal bones|Metacarpal I]] (PSU-5973) |14,130 ± 70 BP |N/A |17,009 ± 135 BP |- |[[Saltville (archaeological site)|Saltville Valley]], [[Virginia]] |M2 molar dentine |14,853 ± 55 BP |N/A |N/A |- |[[Camden County, Missouri|Perkins Cave]], [[Missouri]] |Dentine |16,910 ± 50 BP |N/A |N/A |- |[[Frontier County, Nebraska|La Sena]], [[Nebraska]] |I3 [[incisor]] dentine |19,487 ± 95 BP |19,297–19,677 BP |N/A |- |[[Natural Trap Cave]], [[Wyoming]] |KU 31956 |20,220 ± 150 BP |N/A |24,300 ± 208 BP |- |Cleary ([[Fairbanks, Alaska|Fairbanks]]), [[Alaska]] |F:AM 30492 |20,524 ± 180 BP? |N/A |N/A |- |[[Bonanza Creek|Eldorado Creek (Loc.45)]], [[Yukon]] |[[Calcaneus|Calcaneum]] (CMN37957/FM177762) |22,417 ± 452 BP |N/A |N/A |- |[[Last Chance Creek|Hester Creek]], Hunker Creek, Yukon |NMC-50367 |24,850 ± 150 BP |N/A |N/A |- |[[Ester, Alaska|Ester]] (Fairbanks), Alaska |F:AM 30494 |25,496 ± 224 BP |N/A |N/A |- |[[Dawson City|Gold Run Creek]], Yukon |Cranium (NMC-7438 (<s>NMC 7468</s>)) |26,040 ± 270 BP |N/A |N/A |- |Indet. [[Last Chance Creek|Hunker Creek]], Yukon Hester Creek, Hunker Creek, Yukon |Radius (YG 76.4) Ulna (CMN-49874) |26,520 ± 110 BP¹ 26,720 ± 290 BP |N/A |30,800 BP¹ |- |[[Indian River (Yukon)|Quartz Creek]], Yukon |N/A, YT03/134 |26,940 ± 570 BP |N/A |N/A |- |[[Alaska North Slope|Ikpikpuk River]], Alaska |Humerus (ROM:VP 43646) |27,160 ± 280 BP |N/A |N/A |- |[[Chatanika, Alaska|Upper Cleary Creek]] ([[Fairbanks North Star Borough, Alaska|Fairbanks North Star]]), Alaska |A-37-I0 |27,511 ± 279 |N/A |N/A |- |[[Dawson City|Canyon Creek]], Yukon |Femur (fragment, YG 546.562) |27,850 ± 220 BP |N/A |31,800 BP |- |[[La Brea Tar Pits]], California |Humerus (LACMRLP 19258) [[Metatarsal bones|Metatarsal]] (LACMRLP 54077) [[Cervical vertebrae|Cervical VI]] (LACMRLP 42063) |27,330 ± 140 BP 28,130 ± 330 BP 28,350 ± 470 BP |N/A |N/A |- |[[Dawson City|Lower Hunker Creek (80 pup)]], Yukon |Humerus (NMC 37577) |29,695 ± 1200 BP |N/A |N/A |- |[[Adair County, Oklahoma|Gittin Down Mountain Cave]], [[Oklahoma]] |M2 molar dentine (UAM75-839-1) |34,063 ± 460 BP |33,143–34,983 BP |N/A |- |[[Alleghany County, Virginia|Island Ford Cave]], Virginia |M1 molar dentine (USNM 521336) |34,080 ± 480 BP |33,120–35,040 BP |N/A |- |[[Birch Creek (Yukon River tributary)|Birch Creek]], Alaska |"Birch" |34,974 ± 652 BP |N/A |N/A |- |Ester (Fairbanks), Alaska |AMNH 99209 |39,565 ± 1126 BP |N/A |N/A |- |[[Sixtymile River]] (Loc. 3), Yukon |NMC-42388 |44,240 ± 930 BP |N/A |N/A |- |[[Alaska North Slope|Titaluk River]], Alaska |[[Metapodial]] (UAMES T99-033) |42,600 ± 2,200 BP 46,500 ± 3,600 BP |N/A |43,570 BP 49,016 BP |- |[[Dawson City|Ophir Creek]], Yukon |[[Petrous bone|Petruous bone]] (YG 24.1 / CRH- 95–3) |46,500 BP¹ <s>(20,210 ± 110 BP)</s> |N/A |49,800 BP¹ |} === DNA samples === This table collates the current DNA samples extracted from ''Arctodus'' specimens, with their associated [[haplogroup]]s.<ref name="Pedersen 2728–2736.e8" /><ref name=":28" /><ref name=":49">{{Cite thesis |last=Bray |first=Sarah C. E. |date=September 2010 |title=Mitochondrial DNA Analysis of the Evolution and Genetic Diversity of Ancient and Extinct Bears |url=https://digital.library.adelaide.edu.au/dspace/bitstream/2440/66285/8/02whole.pdf |publisher=School of Environmental and Earth Sciences, University of Adelaide |pages=214 (230)}}</ref><ref name=":11">{{Cite journal |last1=Salis |first1=Alexander T. |last2=Gower |first2=Graham |last3=Schubert |first3=Blaine W. |last4=Soibelzon |first4=Leopoldo H. |last5=Heiniger |first5=Holly |last6=Prieto |first6=Alfredo |last7=Prevosti |first7=Francisco J. |last8=Meachen |first8=Julie |last9=Cooper |first9=Alan |last10=Mitchell |first10=Kieren J. |date=2021-03-10 |title=Ancient genomes reveal hybridisation between extinct short-faced bears and the extant spectacled bear (Tremarctos ornatus) |url=https://www.biorxiv.org/content/10.1101/2021.02.05.429853v2 |language=en |pages=2021.02.05.429853 |doi=10.1101/2021.02.05.429853|s2cid=231885176 }}</ref> {| class="wikitable sortable" |+ !Location !DNA extract ID !<sup>14</sup>C Date (1''σ'') & source !Calibrated dates & Haplogroups |- |[[Chiquihuite cave|Chiquihuite Cave]], [[Zacatecas]] |UE1605 |11,419 ± 34 BP / 11,942 ± 33 / 12,901 ± 75 BP (sediments) |13,000 - 15,000 BP |- |Sheriden Cave, Ohio |ACAD 1734A |11,619 ± 40 BP phalange, CMNHS VP8289) |Haplogroup E |- |Eldorado Creek (Loc.45), Yukon |ACAD 424A/NC011116 |22,417 ± 452 BP (calcaneum, CMN37957/FM177762)) |Haplogroup A |- |"Alaska" |ACAD 450A |25,264 ± 650 BP (humerus, AMNH "ALASKA Bx35‟) |Haplogroup A |- |Hester Creek, Yukon |ACAD 344 & PH092 |26,520 ± 110 BP (radius, YG 76.4) |30,800 BP, Haplogroup A |- |Hester Creek (Loc.57), Yukon |ACAD 330A & AC688 |26,720 ± 270 BP (ulna, CMN49874) |Haplogroup A |- |[[Indian River (Yukon)|Quartz Creek]], Yukon |ACAD1954A |26,940 ± 570 BP (N/A, YT03/134) |Haplogroup D |- |Canyon Creek, Yukon |N/A |27,850 ± 220 BP (femur, YG 546.562) |31,800 BP |- |Sixtymile, Yukon |ACAD 438A & IB187 |44,240 ± 930 BP (metacarpal, CMN 42388) |Haplogroup F |- |Ophir Creek, Yukon |PH095 |46,500 BP (petruous bone, YG 24.1) |49,800 BP, Haplogroup F |- |[[Edmonton]] (Pit #48), [[Alberta]] |ACAD 346A |Radius, P96.2.38 |Haplogroup F |- |Gold Run, Yukon |ACAD 428A |Femur, CMN34556 |Haplogroup A |- |[[Goldstream, Alaska|Goldstream]], Alaska |ACAD 436A |Ulna (pathology), AMNH A-1828 |Haplogroup B |- |Goldstream, Alaska |ACAD 437A |Radius, #850 575 UCLA |Haplogroup C |- |Ester Creek, Alaska |ACAD 441A |Humerus, FAM 95656 |Haplogroup A |- |No.2 G-Strip Area ("Goldstream"), Alaska |ACAD 443A |Ramus, AMNH A-82- 1039 |Haplogroup G |- |Natural Trap Cave, Wyoming |ACAD 5177 |KU 31956 |N/A |- |[[Ester, Alaska|Eva Creek Mine]], Alaska |BS3 |Femur, PM-97-001-100 |Haplogroup D |- |Hunker Creek (80 Pup), Alaska |BS71 |N/A, CMN 44566 |Haplogroup A |- |"[[Dawson City|Dawson area]]", Yukon |BS72 |Tibia, CMN 36236 |Haplogroup D |- |Hunker Creek, Yukon |BS73 |N/A, CMN 42335 |Haplotype A |- |[[Livengood, Alaska|Lillian Creek]], Alaska |BS74 |Humerus, UAF/Paleo V-55-524 |Haplogroup A |- |[[North Pole, Alaska|Dawson Cut]], Alaska |IB191 |Fibula, AMNH A-676- 5625 |Haplogroup F |- |[[Fort Selkirk|Cripple Creek]], Yukon |IB195 |Tibia, AMNH A-217- 2297 |Haplogroup F |- |Dawson, Yukon |IB255 |N/A, CMN 37577 |Haplogroup A |- |Hester Creek, Yukon |JW131 |Ulna, YT03/288 Cat. No. 129.1 (JS) |Haplogroup A |} ==== Haplotype cladogram ==== Below is a cladogram exploring the relationships between the [[Mitochondrial DNA|mitochondrial]] haplogroups of ''Arctodus simus''. Other than the specimen from [[Chiquihuite cave]], all specimens form a single clade.<ref name="Pedersen 2728–2736.e8" /><ref name=":49" />{{clade sequential |1={{clade |1=''[[Tremarctos]]'' [[File:Spectacled bear (1829).jpg|75px]] |2=''[[Arctotherium]]'' }} |2=Chiquihuite Cave |3={{clade |1=A |2=B |3=C }} |4={{clade |1=D |2=E }} |5={{clade |1=F |2=G }} }} ==See also== *''[[Arctotherium]]'' *''[[Agriotherium]]'' *[[Pleistocene megafauna]] *[[Quaternary extinction|Quaternary Extinction Event]] ==References== {{commons category|Arctodus}} {{Reflist}} {{Ursidae extinct nav}} {{Taxonbar|from=Q2626037}} [[Category:Pleistocene bears]] [[Category:Pleistocene carnivorans]] [[Category:Pleistocene extinctions]] [[Category:Prehistoric mammals of North America]] [[Category:Pleistocene mammals of North America]] [[Category:Extinct animals of the United States]] [[Category:Extinct animals of Mexico]] [[Category:Fossil taxa described in 1854]] [[Category:Apex predators]]'
New page wikitext, after the edit (new_wikitext)
'{{Short description|Extinct genus of bears}} {{Automatic taxobox | fossil_range = [[Pleistocene]], {{fossil range|2.5|0.012}} | image = Arctodus simus Page.jpg | image_caption = ''A. simus'' from the [[La Brea tar pits]] | taxon = Arctodus | authority = [[Joseph Leidy|Leidy]], 1854 | type_species = {{extinct}}'''''Arctodus pristinus''''' | type_species_authority = [[Joseph Leidy|Leidy]], 1854 | subdivision_ranks = Other species | subdivision = *{{extinct}}'''''A. simus''''' <small>([[Edward Drinker Cope|Cope]], 1879)</small> | range_map = Short Faced Bear Range.png | range_map_caption = ''Arctodus simus'' range | synonyms = {{collapsible list|bullets=true|title=Species synonymy |{{collapsible list|bullets=true|title=''A. simus'': |''[[Arctotherium]] californicum'' {{small|[[John Campbell Merriam|Merriam]] 1911}} |''Arctotherium simum'' {{small|[[Edward Drinker Cope|Cope]] 1879}} |''Arctotherium yukonense'' {{small|[[Lawrence Lambe|Lambe]] 1911}} |''Dinarctotherium merriami'' {{small|[[Erwin Hinckley Barbour|Barbour]] 1916}} |''Tremarctotherium simum'' {{small|[[James W. Gidley|Gidley]] 1928}} }} |{{collapsible list|bullets=true|title=''A. pristinus'': |''Arctodus haplodon'' {{small|[[Oliver Perry Hay|Hay]] 1902}} |''[[Arctotherium]] pristinum'' {{small|[[Edward Drinker Cope|Cope]] 1895}} |''[[Ursus]] haplodon'' {{small|[[Edward Drinker Cope|Cope]] 1896}} |''[[Tremarctos]] haplodon'' {{small|[[Édouard Louis Trouessart|Trouessart]] 1897}} }} }} }}'''''Arctodus''''' is an extinct genus of [[short-faced bear]] that inhabited [[North America]] during the [[Pleistocene]] (~2.5 [[Year#mya|Mya]] until 12,000 years ago). There are two recognized species: the '''lesser short-faced bear''' (''Arctodus pristinus'') and the '''giant short-faced bear''' (''Arctodus simus''). Both species are relatively rare in the fossil record- ''A. pristinus'' was largely restricted to the Early Pleistocene of the eastern United States, whereas ''A. simus'' had a cosmopolitan range, with most finds being from the Late Pleistocene of the US, Mexico and Canada. ''A. simus'' evolved from ''A. pristinus'', but both species likely overlapped in the Middle Pleistocene. Of these species, ''A. simus'' was larger, is known from more complete remains, and is considered one of the most charismatic of North America's megafauna. Today considered to be an enormous omnivore, ''Arctodus simus'' is believed to be one of the largest known terrestrial mammalian [[carnivora]]ns that has ever existed. However, ''Arctodus'', like other bears, was highly sexually dimorphic. Adult ''A. simus'' ranged between 300&nbsp;kg to 950&nbsp;kg, with females clustering at ≤500&nbsp;kg, and males around 800&nbsp;kg. The largest males stood at 1.5 meters at the shoulder, and up to 3 meters tall on their rear legs. Studies suggest that ''Arctodus simus'' both browsed on vegetation and consumed browsing herbivores, such as [[deer]], [[Camelidae|camelids]], and [[Tapirus|tapir]]. ''A. simus'' seems to have preferred open woodlands, but was an adaptable species, taking advantage of many habitats and feeding opportunities. ''Arctodus'' belongs to the [[Tremarctinae]] subfamily of bears, which are endemic to the [[Americas]]. Of these short-faced bears, ''Arctodus'' was the most widespread in North America. However, both species went extinct in the Pleistocene. ''A. pristinus'' went extinct around 300,000 years ago, with ''A. simus'' disappearing ~12,000 years ago in the [[Quaternary extinction event]], being one of the last recorded megafauna to go extinct in North America. The cause behind these extinctions is unclear, but in the case of ''A. pristinus'', this was likely due to climate change and competition with other ursids, such as the [[American black bear|black bear]] and ''[[Tremarctos floridanus]]''. ''A. simus'' likely went extinct due to ecological collapse disrupting the vegetation and prey ''A. simus'' relied on. ==Taxonomy== ''Arctodus'' was first described by [[Joseph Leidy]] in 1854, with finds of ''A. pristinus'' from the [[Northbridge Park|Ashley Phosphate Beds]], [[South Carolina]].<ref name=":262">{{Cite web |date=2017-03-30 |title=Arctodus pristinus |url=https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/arctodus-pristinus/ |access-date=2022-02-21 |website=Florida Museum |language=en-US}}</ref><ref name=":5" /><ref>{{Cite journal |date=1879-08-01 |title=South Carolina Fossils |url=https://www.nature.com/articles/020354a0 |journal=Nature |language=en |volume=20 |issue=510 |pages=354–355 |doi=10.1038/020354a0 |bibcode=1879Natur..20..354. |s2cid=4034608 |issn=1476-4687}}</ref> The scientific name of the genus, ''Arctodus'', derives from [[Greek language|Greek]], and means "bear tooth". The first fossils of ''A. simus'' were found in the Potter Creek Cave, [[Shasta County, California|Shasta County]], [[California]], by J. A. Richardson in 1878, and were described by [[Edward Drinker Cope]] in 1879.<ref name=":48">{{Cite journal |last=Cope E. D. |year=1879 |title=The cave bear of California |journal=American Naturalist |volume=13 |page=791}}</ref><ref>{{Cite journal |last=Feranec |first=Robert S. |date=2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |journal=Radiocarbon |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |doi-access=free }}</ref><ref>{{Citation |last1=Merriam |first1=John C. |title=Relationships and Structure of the Short-Faced Bear, Arctotherium, from the Pleistocene of California |date=1925 |url=https://resolver.caltech.edu/CaltechAUTHORS:20191008-132308406 |pages=1–25 |place=Washington, DC |publisher=Carnegie institution of Washington |language=en |access-date=2022-05-06 |last2=Stock |first2=Chester}}</ref> The most nearly complete skeleton of ''A. simus'' found in the [[United States|US]] was unearthed in [[Fulton County, Indiana|Fulton County]], [[Indiana]]; the original bones are in the [[Field Museum of Natural History]], [[Chicago]].<ref name=":39">{{Cite book |last1=Richards |first1=Ronald L. |url=https://www.biodiversitylibrary.org/bibliography/3480 |title=Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, northern Indiana |last2=Neiburger |first2=Ellis J. |last3=Turnbull |first3=William D. |date=1995 |publisher=Field Museum of Natural History |location=Chicago, Ill. }}</ref><ref>{{Cite book |last=Stark |first=Mike |url=https://books.google.com/books?id=hWhgEAAAQBAJ&dq=field+museum+rochester+arctodus&pg=PA122-IA12 |title=Chasing the Ghost Bear: On the Trail of America's Lost Super Beast |date=2022 |publisher=U of Nebraska Press |isbn=978-1-4962-2902-1 |pages=Fig. 19 }}</ref> In the 19th and early 20th centuries, specimens of ''Arctodus'' were occasionally referred to ''[[Arctotherium]]'', and vice versa.<ref>{{Cite web |title=Arctodus |url=https://www.utep.edu/leb/pleistnm/taxaMamm/Arctodus.htm#:~:text=Synonyms.,Arctotherium%20simum,%20Tremarctotherium%20simum |access-date=2022-05-05 |website=www.utep.edu}}</ref><ref>{{Cite book |last1=Spamer |first1=Earle E. |url=https://books.google.com/books?id=3loD7lTLBxgC&dq=Arctodus+haplodon&pg=PA204 |title=A Study of Fossil Vertebrate Types in the Academy of Natural Sciences of Philadelphia: Taxonomic, Systematic, and Historical Perspectives |last2=Daeschler |first2=Edward |last3=Philadelphia |first3=Academy of Natural Sciences of |last4=Vostreys-Shapiro |first4=L. Gay |date=1995 |publisher=Academy of Natural Sciences |isbn=978-0-910006-51-4 |language=en}}</ref><ref>{{Cite book |last=Hay |first=Oliver Perry |url=https://books.google.com/books?id=mkMZAAAAYAAJ&q=haplodon&pg=PA763 |title=Bibliography and Catalogue of the Fossil Vertebrata of North America |date=1901 |publisher=U.S. Government Printing Office |language=en}}</ref><ref>{{Citation |last1=Merriam |first1=John C. |title=Relationships and Structure of the Short-Faced Bear, Arctotherium, from the Pleistocene of California |date=1925 |url=https://resolver.caltech.edu/CaltechAUTHORS:20191008-132308406 |pages=1–25 |place=Washington, DC |publisher=Carnegie institution of Washington |language=en |access-date=2022-06-09 |last2=Stock |first2=Chester}}</ref> However, today neither genera are considered to have overlapped, with the closest point of contact being [[Mexico|México]]; the giant ''Arctodus simus'' in [[Hueyatlaco|Valsequillo]], [[Puebla]], and the smaller ''[[Arctotherium|Arctotherium wingei]]'' in the [[Yucatán Peninsula]].<ref name=":352">{{Cite journal |last1=Ferrusquía-Villafranca |first1=Ismael |last2=Arroyo-Cabrales |first2=Joaquín |last3=Martínez-Hernández |first3=Enrique |last4=Gama-Castro |first4=Jorge |last5=Ruiz-González |first5=José |last6=Polaco |first6=Oscar J. |last7=Johnson |first7=Eileen |date=2010-04-15 |title=Pleistocene mammals of Mexico: A critical review of regional chronofaunas, climate change response and biogeographic provinciality |url=https://www.sciencedirect.com/science/article/pii/S104061820900442X |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |language=en |volume=217 |issue=1 |pages=53–104 |doi=10.1016/j.quaint.2009.11.036 |bibcode=2010QuInt.217...53F |issn=1040-6182}}</ref><ref>{{Cite journal |last1=Arroyo-Cabrales |first1=Joaquín |last2=Polaco |first2=Oscar J. |last3=Johnson |first3=Eileen |last4=Ferrusquía-Villafranca |first4=Ismael |date=2010-02-01 |title=A perspective on mammal biodiversity and zoogeography in the Late Pleistocene of México |url=https://www.sciencedirect.com/science/article/pii/S1040618209001633 |journal=Quaternary International |series=Quaternary Changes of Mammalian Communities Across and Between Continents |language=en |volume=212 |issue=2 |pages=187–197 |doi=10.1016/j.quaint.2009.05.012 |bibcode=2010QuInt.212..187A |issn=1040-6182}}</ref><ref name=":25" /> Conversely, fossils of ''Arctodus pristinus'' are often confused with the similarly sized, partially contemporaneous [[Tremarctinae|short-faced bear]], ''Tremarctos floridanus''.<ref name=":262"/> Sometimes described as the "American cave bear", ''Arctodus'' should not be mistaken for the similarly large [[Cave bear|Eurasian cave bear]] (''Ursus speleaus'').<ref name=":48" /> As an ursine, the Eurasian cave bear last shared a common ancestor with the tremarctine ''Arctodus'' circa 13.4 million years ago.<ref name="Pedersen 2728–2736.e8" /> ===Evolution=== {{Cladogram|{{clade| style=font-size:90%;line-height:90%; |1={{dagger}}[[Hemicyoninae]] |2={{Clade |1={{dagger}}[[Ursavinae]] |2={{Clade |1={{dagger}}[[Agriotheriinae]] |2={{Clade |1=[[Ailuropodinae]] [[File:Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg|75px]] |2={{Clade |1=[[Ursinae]] [[File:Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|75px]] |2={{Clade |label1=[[Tremarctinae]] (short-faced bears) |1={{Clade |1={{dagger}}''[[Plionarctos]]'' |2={{Clade |1={{dagger}}'''''Arctodus''''' |2={{Clade |1=''[[Tremarctos]]'' [[File:Spectacled bear (1829).jpg|75px]] |2={{dagger}}''[[Arctotherium]]'' }} }} }} }} }} }} }} }} }}|title=[[Tremarctinae]] within [[Ursidae]]|align=left}} ''Arctodus'' belongs to a group of bears known as the short-faced bears ([[Tremarctinae]]), which appeared in [[North America]] during the earliest parts of the late [[Miocene]] epoch in the form of ''[[Plionarctos]]'', a genus considered ancestral to Tremarctinae. ''[[Plionarctos]]'' gave way to the medium-sized ''Arctodus pristinus,'' ''Tremarctos floridanus'' and ''Arctotherium sp.'' in the [[Blancan|Blancan age]] of [[North America]],<ref name=":5">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |s2cid=168164209 }}</ref><ref name=":18">{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Romero |first2=M.R. Aguilar |date=2008-10-14 |title=A Blancan (Pliocene) short-faced bear from El Salvador and its implications for Tremarctines in South America |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=250 |issue=1 |pages=1–8 |doi=10.1127/0077-7749/2008/0250-0001 |url=http://sedici.unlp.edu.ar/handle/10915/5361 }}</ref><ref name=":02">{{Cite journal |last1=Schubert |first1=Blaine |last2=Hulbert |first2=Richard |last3=MacFadden |first3=Bruce |last4=Searle |first4=Michael |last5=Searle |first5=Seina |date=2010-01-01 |title=Giant Short-faced Bears (Arctodus simus) in Pleistocene Florida USA, a Substantial Range Extension |url=https://www.researchgate.net/publication/250071137 |journal=Journal of Paleontology |volume=84 |pages=79–87 |doi=10.1666/09-113.1 |s2cid=131532424}}</ref> with the genetic divergence date for ''Arctodus'' being ~5.5 million years ago.<ref name="Pedersen 2728–2736.e8" /> Both ''Arctodus'' and ''[[Tremarctos]]'' were largely restricted to the more forested eastern part of the continent, as ''[[Borophagus|Boropahgus]]'' and ''[[Agriotherium]]'' are thought to have limited [[Tremarctinae|tremarctine]] presence in the more open Western [[North America]]. ''Tremarctos floridanus'' established a range mostly hugging the [[Gulf of Mexico|Gulf Coast]] (but also extending to [[California]], [[Idaho]] and [[Belize]]),<ref name=":02"/> whereas ''Arctodus pristinus'' ranged from [[Aguascalientes]], Mexico,<ref>{{Cite journal |last1=Dalquest |first1=W. W. |last2=Mooser |first2=O. |date=1980-12-19 |title=Arctodus pristinus Leidy in the Pleistocene of Aguascalientes, Mexico |journal=Journal of Mammalogy |volume=61 |issue=4 |pages=724–725 |doi=10.2307/1380320 |jstor=1380320 }}</ref> to [[Port Kennedy Bone Cave|Port Kennedy]], Pennsylvania, in the US.<ref name="researchgate.net">{{Cite journal |last1=Daeschler |first1=Edward B. |last2=Spamer |first2=Earl E. |last3=Parris |first3=David C. |date=1993 |title=Review and New Data on the Port Kennedy Local Fauna and Flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania |url=https://www.researchgate.net/publication/325630951 |journal=The Mosasaur - Delaware Valley Paleontological Society |volume=5 |pages=23–41 |via=ResearchGate}}</ref> Perhaps due to their evolutionary history, both ''[[Tremarctos floridanus]]'' and ''Arctodus pristinus'' have the greatest concentration of fossils in [[Florida]]- ''A. pristinus'' is first known from the [[Santa Fe River (Florida)|Santa Fe River 1 site]] of [[Gilchrist County, Florida|Gilchrist County]]. However, in the [[Quaternary|early Quaternary]], when both ''[[Borophagus]]'' and ''[[Agriotherium]]'' went extinct, ''Arctodus'' would take advantage and spread into the rest of the continent, primarily in the form of ''A. simus''. Concurrently, during the [[Great American Interchange]] that followed the joining of North and South America, the [[Central America]]n based ''Arctotherium'' invaded [[South America]],<ref name=":18" /> leading to the diversification of the genus, including the colossal ''[[Arctotherium|Arctotherium angustidens]]''. During the early [[Irvingtonian]] (~1.1 million years ago), the smaller ''A. pristinus'' was joined by the enormous ''A. simus''.<ref>{{Cite book |last1=Bell |first1=Christopher |url=https://www.researchgate.net/publication/263425514 |title=Late Cretaceous and Cenozoic Mammals of North America |last2=Lundelius |first2=Ernest L. |last3=Barnosky |first3=Anthony D. |last4=Zarzewski |first4=Richard J. |last5=Graham |first5=Russell |last6=Lindsay |first6=Everett H. |last7=Ruez |first7=Dennis R. |last8=Semken |first8=Holmes A. |last9=Webb |first9=S. David |date=2004-04-21 |publisher=Columbia University Press |isbn=978-0-231-50378-5 |language=en |chapter=Chapter 7: The Blancan, Irvingtonian, and Rancholabrean Mammal Ages |doi=10.7312/wood13040}}</ref> The two are differentiated not only by size, but also by the shorter snout, more robust teeth and longer limbs of ''A. simus,'' and the relative proportions of each species' molars and premolars. However, there are relatively few morphological differences. As a result, differentiating ''Arcotdus simus'' from ''Arctodus pristinus'' can be difficult, as large individuals of ''Arctodus pristinus'' can overlap in size with small individuals of ''Arctodus simus''.<ref name=":02"/> ''A. simus'' is first recorded from the Irvington type locality in California. Although both species co-existed for at least half a million years (''A. pristinus'' went extinct ~300,000 BP), there is no direct evidence of [[sympatry]] or [[Competition (biology)|competition]] in the fossil record as of yet.<ref name=":02"/> However, there are unreliable records of ''A. pristinus'' in [[South Carolina]], [[California]] and [[Florida]] in the [[Late Pleistocene]], suggesting a possible existence as a [[Relict (biology)|relict species]] in [[Refugium (population biology)|refugia]] until the [[Quaternary extinction|Quaternary extinction event]].<ref>{{Cite journal |last1=Feranec |first1=Robert S. |last2=Hadly |first2=Elizabeth A. |last3=Blois |first3=Jessica L. |last4=Barnosky |first4=Anthony D. |last5=Paytan |first5=Adina |date=2007 |title=Radiocarbon Dates from the Pleistocene Fossil Deposits of Samwel Cave, Shasta County, California, USA |journal=Radiocarbon |volume=49 |issue=1 |pages=117–121 |doi=10.1017/S0033822200041941 |s2cid=130708736 |doi-access=free }}</ref><ref name=":8">{{Cite book |last=Sanders |first=Albert E. |url=https://books.google.com/books?id=LS8LAAAAIAAJ&dq=pristinus+south+carolina&pg=PA48 |title=Additions to the Pleistocene Mammal Faunas of South Carolina, North Carolina, and Georgia |date=2002 |publisher=American Philosophical Society |isbn=978-0-87169-925-1 }}</ref><ref name=":92">{{Cite web |last1=Esker |first1=Donald |last2=Wilkins |first2=William |last3=Agenbroad |first3=Larry |date=2010-08-13 |title=Esker, Wilkins, and Agenbroad—Multivariate Analysis Of Ursids: A multivariate analysis of the ecology of North American Pleistocene bears, with a focus on ''Arctodus simus'' |website=ResearchGate |url=https://www.researchgate.net/publication/314037201}}</ref> Likewise, ''Arctodus simus'' is relatively poorly known from the [[Irvingtonian]] (1,900,000 BP-250,000 BP) with finds mostly from California, with additional remains from Texas, Kansas, Nebraska, and Montana.<ref name=":46" /><ref name=":4" /> In any case, whereas ''A. pristinus'' seems to have preferred the more heavily forested thermal enclave in eastern North America,<ref name=":10">{{Cite journal |last1=Russell |first1=Dale A. |last2=Rich |first2=Fredrick J. |last3=Schneider |first3=Vincent |last4=Lynch-Stieglitz |first4=Jean |date=May 2009 |title=A warm thermal enclave in the Late Pleistocene of the South-eastern United States |journal=Biological Reviews |volume=84 |issue=2 |pages=173–202 |doi=10.1111/j.1469-185X.2008.00069.x |pmid=19391200 |s2cid=9609391 }}</ref> ''A. simus'' was a cosmopolitan, eventually pan-continental species in the Late Pleistocene- sharing that distinction with the [[American black bear|black bear]], and the [[brown bear]] after 100,000 BP.<ref name=":92"/> Primarily inhabiting a range from southern [[Canada]] to [[Puebla|Central Mexico]] in the west, to [[Pennsylvania]] and [[Florida]] in the east,<ref name=":25">{{Cite book|last1=Richards|first1=Ronald L. |title=Distribution and size variation in North American Short-faced bears, Arctodus simus|last2=Churcher|first2=C. S.|last3=Turnbull|first3=William D.|date=2019-11-18|publisher=University of Toronto Press|isbn=978-1-4875-7415-4 |doi=10.3138/9781487574154-012}}</ref><ref name=":02"/><ref>{{Cite journal |last1=Steffen |first1=Martina L. SteffenM L. |last2=Harington |first2=C. R. HaringtonC R. |date=2010-07-23 |title=Giant short-faced bear (Arctodus simus) from late Wisconsinan deposits at Cowichan Head, Vancouver Island, British Columbia |url=https://cdnsciencepub.com/doi/abs/10.1139/E10-018 |journal=Canadian Journal of Earth Sciences |volume=47 |issue=8 |pages=1029–1036 |language=en |doi=10.1139/E10-018|bibcode=2010CaJES..47.1029S }}</ref><ref>{{Cite journal |last=Cassiliano M. L. |year=1999 |title=Biostratigraphy of Blancan and Irvingtonian mammals in the Fish Creek-Vallecito Creek section, southern California, and a review of the Blancan-Irvingtonian boundary |journal=Journal of Vertebrate Paleontology |volume=19 |issue=1 |pages=169–186 |doi=10.1080/02724634.1999.10011131}}</ref><ref>{{cite journal |last1=Carranza-Castañeda |first1=Oscar |last2=Miller |first2=Wade E. |title=Rediscovered type specimens and other important published Pleistocene mammalian fossils from Central Mexico |journal=Journal of Vertebrate Paleontology |date=16 September 1987 |volume=7 |issue=3 |pages=335–341 |doi=10.1080/02724634.1987.10011664 }}</ref><ref name=":24">{{Cite journal |last1=Holliday |first1=Vance |last2=Surovell |first2=Todd |last3=Meltzer |first3=David |last4=Grayson |first4=Donald |last5=Boslough |first5=Mark |date=2014-08-01 |title=The Younger Dryas impact hypothesis: A cosmic catastrophe |url=https://www.researchgate.net/publication/265132201 |journal=Journal of Quaternary Science |volume=29 |issue=6 |pages=515–530 |doi=10.1002/jqs.2724|bibcode=2014JQS....29..515H |s2cid=18644154 }}</ref> ''A. simus'' is particularly famous from fossils found in the [[La Brea tar pits]] in southern [[California]].<ref name="Bearalmanac">{{Cite book |last=Brown, Gary |url=https://archive.org/details/greatbearalmanac00gary/page/340 |title=Great Bear Almanac |year=1996 |isbn=978-1558214743 |page=[https://archive.org/details/greatbearalmanac00gary/page/340 340] |url-access=registration}}</ref> From ~50,000 BP to ~23,000 BP, ''A. simus'' also inhabited [[Beringia]]- finds today span from northern [[Alaska]] to the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /><ref name=":02"/><ref name=":24" /><ref>C. S. Churcher, A. V. Morgan, and L. D. Carter. 1993. ''Arctodus simus from the Alaskan Arctic Slope''. Canadian Journal of Earth Sciences 30(5):1007-1013, collected by A. V. Morgan</ref> The [[Late Pleistocene]] represents the peak of [[Bear|ursid]] diversity in [[Quaternary]] [[North America]], with ''Arctodus simus,'' [[brown bear]]s, [[American black bear|black bears]], ''[[Tremarctos floridanus]]'', and ''[[Arctotherium|Arctotherium wingei]]'' all roaming south of the [[Laurentide Ice Sheet]],<ref name=":19">{{cite bioRxiv |last1=Salis |first1=Alexander T |last2=Bray |first2=Sarah C E |last3=Lee |first3=Michael S Y |last4=Heiniger |first4=Holly |last5=Barnett |first5=Ross |last6=Burns |first6=James A |last7=Doronichev |first7=Vladimir |last8=Fedje |first8=Daryl |last9=Golovanova |first9=Liubov |last10=Harington |first10=C Richard |last11=Hockett |first11=Bryan |last12=Kosintsev |first12=Pavel |last13=Lai |first13=Xulong |last14=Mackie |first14=Quentin |last15=Vasiliev |first15=Sergei |last16=Weinstock |first16=Jacobo |last17=Yamaguchi |first17=Nobuyuki |last18=Meachen |first18=Julie |last19=Cooper |first19=Alan |last20=Mitchell |first20=Kieren J |title=Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge |date=3 September 2020 |biorxiv=10.1101/2020.09.03.279117}}</ref><ref>{{Cite journal|last1=Schubert|first1=Blaine W.|last2=Chatters|first2=James C.|last3=Arroyo-Cabrales|first3=Joaquin|last4=Samuels|first4=Joshua X.|last5=Soibelzon|first5=Leopoldo H.|last6=Prevosti|first6=Francisco J.|last7=Widga|first7=Christopher|last8=Nava|first8=Alberto|last9=Rissolo|first9=Dominique|last10=Erreguerena|first10=Pilar Luna|date=May 2019|title=Yucatán carnivorans shed light on the Great American Biotic Interchange|journal=Biology Letters|volume=15|issue=5|pages=20190148|doi=10.1098/rsbl.2019.0148 |pmc=6548739|pmid=31039726}}</ref> and [[polar bear]]s above the ice.<ref>{{Cite journal|last1=Arroyo-Cabrales|first1=Joaquin|last2=Johnson|first2=Eileen|last3=Graham|first3=Ruswell|last4=perez crespo|first4=Victor|date=2016-07-24|title=North American ursid (Mammalian: Ursidae) defaunation from Pleistocene to recent.|url=https://www.researchgate.net/publication/305681538|journal=Cranium|volume=33|pages=51–56}}</ref><ref name=":112">{{Cite book |last=Pérez-Crespo |first=J. Arroyo-Cabrales E. Johnson R.W. Graham V.A. |title=North American ursid (mammalia: ursidae) defaunation from Pleistocene to recent |date=2016-01-01 |oclc=1227719621}}</ref> However, despite ''Arctodus simus''<nowiki/>' large temporal and geographic range, fossil remains are comparatively rare (109 finds as of 2010, in otherwise well-sampled localities).<ref name=":02"/><ref name="Pedersen 2728–2736.e8">{{Cite journal|last1=Pedersen|first1=Mikkel Winther|last2=De Sanctis|first2=Bianca|last3=Saremi|first3=Nedda F.|last4=Sikora|first4=Martin|last5=Puckett|first5=Emily E.|last6=Gu|first6=Zhenquan|last7=Moon|first7=Katherine L.|last8=Kapp|first8=Joshua D.|last9=Vinner|first9=Lasse|last10=Vardanyan|first10=Zaruhi|last11=Ardelean|first11=Ciprian F.|date=2021-06-21|title=Environmental genomics of Late Pleistocene black bears and giant short-faced bears |journal=Current Biology |volume=31|issue=12|pages=2728–2736.e8|doi=10.1016/j.cub.2021.04.027|pmid=33878301|s2cid=233303447 |hdl=10037/22808|hdl-access=free}}</ref> === Genetic diversity === An examination of mitochondrial DNA sequenced from specimens of ''Arctodus simus'' from Alaska, Yukon, Alberta and Ohio suggest an extremely low level of genetic diversity among the 23 individuals studied (≤ 44,000 [[Radiocarbon dating|<sup>14</sup>C]] BP), with only seven haplotypes recovered, forming a monophyletic clade. Genetic diversity was comparable to modern endangered taxa, such as the brown kiwi and African cheetah. Explanations include a [[Population bottleneck|genetic bottleneck]] before 44,000 <sup>14</sup>C BP, or a low level of genetic diversity being a feature of a species which was primarily solitary, with a large home range and relatively small population size. However, a similar lack of genetic diversity across large geographic areas can be found in some hyenas in Africa, such as the [[striped hyena]] and [[brown hyena]].<ref name=":49" /> However, this does not entirely preclude genetic diversity in ''Arctodus simus'', with genetic samples from [[Chiquihuite cave]], Mexico (~14,000 BP), indicating a deep divergence with previously studied specimens of ''A. simus''.<ref name="Pedersen 2728–2736.e8" /> ==Description== === Size === [[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and {{Convert|317|kg|lb|abbr=on}}, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" /> Though over 100 giant short-faced bear localities in [[North America]] are known, only one site produced a [[baculum]] (penis bone) that could belong to ''Arctodus simus''. The lack of recovered ''Arctodus'' [[Baculum|bacula]] likely reflects both [[taphonomy]] and behaviour. The majority of skeletal remains representing large individuals are from open sites where usually only a few elements were recovered. In contrast, horizontal (walk-in) cave passages produced numerous examples of small, yet relatively complete individuals where [[Baculum|bacula]] would likely be found if they had been present. Both the small size of recovered skeletal elements and the lack of [[Baculum|bacula]] from cave deposits suggest that female individuals of ''A. simus'' were using caves, in line with [[Bear|ursid]] maternal denning.<ref name=":2">{{Cite journal|last1=CHUBERT|first1=BLAINE|last2=KAUFMANN|first2=JAMES|date=2003-08-01|title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species|url=https://www.researchgate.net/publication/252748398|journal=Journal of Cave and Karst Studies|volume=65}}</ref><ref name=":3">{{Cite journal|last1=Fowler|first1=Nicholas L.|last2=Spady|first2=Thomas J.|last3=Wang|first3=Guiming|last4=Leopold|first4=Bruce D.|last5=Belant|first5=Jerrold L.|date=October 2021|title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51|issue=4|pages=465–481|doi=10.1111/mam.12246|s2cid=233847639 }}</ref> Therefore, in conjunction with ursid sexual dimorphism (e.g. in [[spectacled bear]]s, males are 30%-40% larger than females), the largest individuals are often considered male, particularly older males, with the smaller individuals being females.<ref name=":02"/><ref name=":12">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |doi=10.1016/j.quaint.2009.11.010 |bibcode=2010QuInt.217..188S }}</ref><ref name=":46">{{Cite journal |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |journal=PaleoBios |volume=15 |issue=2 |pages=27–36 |date=May 24, 1993 |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf}}</ref> Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~{{Convert|555|kg|lb}}.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1998 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~{{Convert|372|kg|lb}}, smaller than recovered [[brown bear]] remains (~{{Convert|455|kg|lb}}, although these remains postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~{{Convert|770|kg|lb}} from six specimens.<ref name=":7" /> Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between {{Convert|1200|kg|lb}} and {{Convert|412|kg|lb}},<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between {{Convert|957|kg|lb}} and {{Convert|317|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref> === Data === Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]],<ref name=":6" /><ref name=":62"/> and some associated weight estimates.<ref name="Figueiridio_et_al_20102" /> Also included is the mean from 9 specimens in [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref> {| class="wikitable sortable" |+ !Element ID & Location !Proximal Length (mm) !Total Length (mm) !Transverse Width (midshaft, mm) !Ratio of TL to TW (M) x 100 !Standard Deviation !Estimated weight (kg) |- |P.89.13.91, [[Edmonton]] |585 |707 (est.) |63.2 |9.0 |~ |~ |- |UVP 015/1, Utah |598 |723 |64 |8.9 |~ |957 |- |UC 3721, [[Shasta Lake|Potter Creek Cave]] |~ |524 |43.3 |8.3 |~ |~ |- |F:AM 25531, [[Hay Springs, Nebraska|Hay Springs]] |~ |658 |62.6 |9.5 |~ |863 |- |UM 25611, [[Meade, Kansas|Jinglebob]] |~ |507 |43.3 |8.5 |~ |388 |- |UC 44687, [[Irvington, California|Irvington]] |~ |678 |62 |9.1 |~ |~ |- |LACMNH-Z75, [[La Brea Tar Pits|Rancho La Brea]] |444 |~ |42.3 |~ |~ |317 |- |U.S.A. sites, x̄ values (Kurtén, 1967) |~ |584 |47.8 |8.1-9.5 (x̄= 8.7) |0.45 |~ |} === Anatomy === ==== Skull ==== [[File:Arctodus simus skull Cleveland.jpg|thumb|''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], [[Ohio]]]] Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] were likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" /> The skull also has a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance; this broad [[snout]] possibly housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas (although this is characteristic shared with the omni-herbivorous spectacled bear).<ref name=":7" /><ref name=":132">{{Cite journal |last1=Emslie |first1=Steven D. |last2=Czaplewski |first2=Nicholas J. |date=1985-11-15 |title=A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology |url=https://www.biodiversitylibrary.org/partpdf/226835 |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793}}</ref><ref name=":402">{{Cite journal |last=Matheus |first=Paul E. |date=1995-11-01 |title=Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0033589485710903 |journal=Quaternary Research |language=en |volume=44 |issue=3 |pages=447–453 |doi=10.1006/qres.1995.1090 |bibcode=1995QuRes..44..447M |s2cid=83542760 |issn=0033-5894}}</ref><ref>{{Cite journal |last1=Goswami |first1=Anjali |last2=Milne |first2=Nick |last3=Wroe |first3=Stephen |date=2011-06-22 |title=Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1713 |pages=1831–1839 |doi=10.1098/rspb.2010.2031 |issn=0962-8452 |pmc=3097826 |pmid=21106595}}</ref> The [[Orbit (anatomy)|orbits]] of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat [[Lateral (anatomy)|laterally orientated]] (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the [[brown bear]], suggesting that [[Stereopsis|stereoscopic vision]] was not a priority.<ref name=":110"/><ref name=":302"/><ref name=":292">{{Cite book |last=Baryshnikov |first=Gennady |url=https://www.researchgate.net/publication/336916777 |title=The Hot Springs Mammoth Site: A Decade of Field and Laboratory Research in Paleontology, Geology and Paleoecology |publisher=The Mammoth Site of Hot Springs, South Dakota Inc. |year=1994 |editor-last=Agenbroad |editor-first=Larry D. |pages=Chapter 16 |editor-last2=Mead |editor-first2=Jim I.}}</ref> The [[premolar]]s and [[Molar (tooth)|first molars]] of ''Arctodus pristinus'' are relatively smaller and more widely spaced than those of ''Arctodus simus''. However, the morphologies of both species are otherwise very similar. Differentiating between the two can be difficult, as males of ''A. pristinus'' overlap in size with females of ''A. simus''.<ref name=":262"/><ref name=":02"/> The dentition of ''Arctodus'' has been used as evidence of a predatory lifestyle- in particular the large [[Canine tooth|canines]], the high-crowned lower [[first molar]], and the possible [[carnassial shear]] with the upper [[Premolar|fourth premolar]]. However, the wearing of the molars to a relatively flat, blunt loph (suitable as a crushing platform as per modern omnivorous bears), small shear facet, and the flattened [[Cusp (anatomy)|cusps]] across age ranges (unlike carnivores, which instead have [[carnassial shear]]s) suggests an alternative adaptive purpose.<ref name=":132"/> In ''A. pristinus'', the features of the dentition can be quite variable, particularly the M2 molar.<ref name=":5" /> A specimen of ''A. simus'' from the Seale Pit of the Hill-Shuler locality, Texas, with only two premolars, crowding of the anterior premolar out of line, and a wider and shorter muzzle, was even suggested to be an undescribed form of ''Arctodus''.<ref name=":13" /> An analysis of the [[Mandible|mandibular]] morphology of tremarctine bears found that ''Arctodus pristinus'' and ''Arctodus simus'' were divergent in the dimensions of their cranial anatomy, with ''Arctodus simus'' clustering tightly with ''Arctotherium angustidens'', suggesting a similar foraging strategy. ''A. simus'' specimens have a concave jaw, large [[Masseter muscle|masseter]] and [[Temporalis muscle|temporalis]] muscles, deeper horizontal ramus and a reduced slicing dentition length, when compared to ''A. pristinus''. However, both ''A. pristinus'' and ''A. simus'' were still found to be comfortably in the "omnivorous" bear cranio-morphotype, and are interpreted as such, along with ''Arctotherium angustidens''.<ref name=":302"/> ==== Post-cranial ==== [[File:ArctodusSimusReconstruct.jpg|thumb|''A. simus'' compared with a human|left]] Although the shape of the [[Elbow|elbow joint]] suggests ''Arctodus'', ''[[Arctotherium|Arctotherium bonariense]]'', and ''[[Arctotherium|Arctotherium wingei]]'' had the possibility of retaining [[Arboreal locomotion|semi-arboreal]] adaptations, the size of the elbow joint condemns ''Arctodus'' to terrestrial life. As the [[Medial epicondyle of the humerus|medial epicondyle]] is particularly expanded in these species, it is likely that ''Arctodus'' and ''Arctotherium'' (just like the [[giant panda]]) retained this characteristic to attain a higher degree of forelimb dexterity. Whether this dexterity facilitated [[Scavenger|scavenging]] or [[Herbivore|herbivory]], this high degree of proximal dexterity was probably advantageous for these species, and retained in tremarctine bears despite their general tendency towards terrestriality.<ref name=":28">{{Cite journal|last1=Mitchell|first1=Kieren J.|last2=Bray|first2=Sarah C.|last3=Bover|first3=Pere|last4=Soibelzon|first4=Leopoldo|last5=Schubert|first5=Blaine W.|last6=Prevosti|first6=Francisco|last7=Prieto|first7=Alfredo|last8=Martin|first8=Fabiana|last9=Austin|first9=Jeremy J.|last10=Cooper|first10=Alan|date=2016-04-30|title=Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America|journal=Biology Letters|volume=12|issue=4|pages=20160062|doi=10.1098/rsbl.2016.0062|pmc=4881349|pmid=27095265}}</ref><ref name=":132"/><ref name="Meloro 133–146">{{Cite journal|last1=Meloro|first1=Carlo|last2=de Oliveira|first2=Alessandro Marques|date=2019-03-01|title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |journal=Journal of Mammalian Evolution |volume=26|issue=1|pages=133–146|doi=10.1007/s10914-017-9413-x|s2cid=25839635 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf}}</ref> A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" /> ''Arctodus'' likely had a top speed of {{Convert|40-45|km/h|mph}}, and based on hyaenid proportions, would shift from singlefoot locomotion to a pace at {{Convert|8.5|km/h|mph|abbr=on}}, and would begin to gallop at {{Convert|18.5|km/h|mph|abbr=on}}, a fairly high speed. Based on other mammals, the optimal pace speed of ''Arctodus'' would have been {{Convert|13.7|km/h|mph|abbr=on}}, which would have also been rather fast for moderate speed travel. For comparison, hyenas cross country ~{{Convert|10|km/h|mph|abbr=on}}.<ref name=":212" /> The [[paw]]s ([[metapodial]]s and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''' paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the first digit ([[Toe|hallux]]) of ''Arctodus'' was positioned more closely and parallel to the other four digits (i.e. with straight toes, ''Arctodus'' had less lateral splaying).<ref name=":272">{{Cite thesis |title=Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia |url=https://scholarworks.alaska.edu/handle/11122/9491 |date=1997 |degree=PhD |language=en |first=Paul Edward |last=Matheus}}</ref> This theory is potentially contradicted by trackways tentatively attributed to ''Arctodus'' from near [[Lakeview, Oregon|Lakeview]] in [[Oregon]]. The trackways, which fit the dimensions of ''Arctodus simus''<nowiki/>' paws, exhibit extreme toe splaying, with three centrally aligned, evenly spaced toes at the front, and two almost perpendicular toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had an oval-shaped, undivided pad on its sole (with no toe pad impressions), with front paws that were slightly larger than its back paws, possessed long claws, and had its hind foot overstep the forefoot when walking, like modern bears.<ref>{{Cite web |last1=Packard |first1=E.L. |last2=Allison |first2=I.S. |last3=Cressman |first3=L.S. |title=Mammalian Tracks in the Late Pliocene or Early Pleistocene Beds of Lake County Oregon |url=https://www.oregongeology.org/milo/archive/MiningDistricts/LakeCounty/UnclassifiedDistrict/LakeCountyFossilLocalities/LakeCountyFossilLocalitiesReports.pdf |access-date=June 11, 2017 |website=Oregon Geology}}</ref> For comparison, the [[Manus (anatomy)|manus]] of the spectacled bear has five digits arrayed in a shallow arc, and claws which are quite long, and which also extend far in front of their respective digits.<ref>{{Cite journal |last=Weems |first=Robert E. |date=2018 |title=An Early Pleistocene (Early Irvingtonian) Footprint Fauna from the Bacons Castle Formation, Westmoreland Formation, Virginia |url=https://www.researchgate.net/publication/348579743 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=79 |pages=731–748 |via=ResearchGate}}</ref> Some claw marks attributed to ''Arctodus simus'' at [[Riverbluff Cave]] (as they were four meters above the floor of the cave) were nearly 20&nbsp;cm in width.<ref name=":1">{{Cite journal |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |title=Cenozoic Vertebrate Tracks and Traces |last2=Spielmann |first2=Justin A. |last3=Lockley |first3=Martin G. |date=2007 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=42 |language=en}}</ref> The presence of a partial [[Sesamoid bone#Other animals|false thumb]] in ''Arctodus simus'' is a characteristic shared with ''[[Tremarctos floridanus]]'' and the [[spectacled bear]], and is possibly an [[Plesiomorphy and symplesiomorphy|ancestral]] trait. Absent in [[Ursinae|ursines]], the false thumb of the spectacled bear has been suggested to assist in herbivorous food manipulation (such as extracting [[Mast (botany)|mast]], e.g. [[Bromeliaceae|bromelaid]]/[[Heart of palm|palm hearts]]), or [[arboreality]].<ref>{{Cite journal |last1=Salesa |first1=M. J. |last2=Siliceo |first2=G. |last3=Antón |first3=M. |last4=Abella |first4=J. |last5=Montoya |first5=P. |last6=Morales |first6=J. |date=2006-12-30 |title=Anatomy of the "false thumb" of Tremarctos ornatus (Carnivora, Ursidae, Tremarctinae): Phylogenetic and functional implications |url=http://estudiosgeol.revistas.csic.es/index.php/estudiosgeol/article/view/33/32 |journal=Estudios Geológicos |volume=62 |issue=1 |pages=389–394 |doi=10.3989/egeol.0662133 |issn=1988-3250}}</ref> ==== Maturity ==== Examinations on a young individual of ''Arctodus simus'' from an [[Ozarks|Ozark]] cave suggest that ''Arctodus'', like other [[Bear|ursids]], reached [[sexual maturity]] before [[Bone age|osteological maturity]]. Comparisons with known [[Epiphyseal plate|epiphyseal fusion sequences]] in [[American black bear|''Ursus americanus'']] demonstrated that while the individual was not osteologically mature when it died (numerous [[Epiphysis|epiphyses]] were unfused) the stage of fusion of the [[long bone]] [[epiphyseal plate]]s indicated that the specimen was mostly full sized, and was therefore sexually mature well before such fusions are complete. If ''Arctodus'' were similar in their timing of sexual maturity to modern ''Ursus americanus'', then the ''Arctodus'' specimen was already sexually mature, and was either 4–6 years of age if female, or 6–8 years if the specimen was male. Additionally, wear patterns on the individual's teeth are similar to a 4-6 year old ''Ursus americanus''. For comparison, female [[Spectacled bear|''Tremarctos ornatus'']] reach sexual maturity ~4 years of age, female [[American black bear|''Ursus americanus'']] become sexually mature between 2–4 years of age, and female [[Brown bear|''Ursus arctos'']] begin breeding in some portions of their range at around 3 years.<ref name=":2" /> Fused [[Sutures of skull|sutures]] and [[tooth eruption]] have been used to determine adulthood in ''Arctodus''.<ref name="Pedersen 2728–2736.e8" /> ==Paleobiology== [[File:South Florida Museum - Big Carnivore Skeleton.jpg|thumb|A reconstruction of ''Arctodus pristinus'', from the [[Bishop Museum of Science and Nature]], Florida.]] === ''Arctodus pristinus'' === ==== Paleoecology ==== Although smaller than its descendant, ''Arctodus pristinus'' was still a relatively large tremarctine bear.<ref name=":262"/> Sometimes referred to as the eastern short-faced bear,<ref>{{Cite book |last=Grumet |first=Robert S. |title=Bay, Plain, and Piedmont- A Landscape History of the Chesapeake Heartland from 1.3 Billion Years Ago to 2000 |publisher=The Chesapeake Bay Heritage Context Project |date=September 2000 |pages=16, 21, 167}}</ref> ''Arctodus pristinus'' has been found in [[Kansas]], [[South Carolina]], [[Maryland]] and [[Pennsylvania]] in the [[United States|US]], and [[Aguascalientes]] in [[Mexico]].<ref name=":53">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |s2cid=168164209}}</ref><ref name=":822">{{Cite book |last=Sanders |first=Albert E. |url=https://books.google.com/books?id=LS8LAAAAIAAJ&dq=pristinus+south+carolina&pg=PA48 |title=Additions to the Pleistocene Mammal Faunas of South Carolina, North Carolina, and Georgia |date=2002 |publisher=American Philosophical Society |isbn=978-0-87169-925-1}}</ref> In the Early Pleistocene, ''Arctodus pristinus'' was much more populous the south-east of North America, whereas the black bear was more common in the north-east.<ref>{{Cite book |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=ZFfPDwAAQBAJ&dq=Cumberland+Bone+Cave+arctodus&pg=PA740 |title=Fossil Record 6 Volume 2 |last2=Sullivan |first2=Robert M. |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref> ''Arctodus pristinus'' is particularly well known from Florida, especially from the Leisley Shell Pit.<ref>{{Cite journal |last=Berta |first=Annalisa |date=1995 |title=Fossil carnivores from the Leisley Shell Pit, Hillsborough County, Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-14.pdf |journal=Florida Museum of Natural History |volume=37 Part II |issue=14 |pages=436–499}}</ref> ''Arctodus pristinus'' is considered a biochronological indicator for the period between the Late Blancan and late Irvingtonian periods of Pleistocene Florida.<ref name=":5" /> ==== Hibernation ==== ''Arctodus pristinus'' specimens have been found in caves such as [[Port Kennedy Bone Cave|Port Kennedy]], Pennsylvania (where fossils from as many as 36 individuals have been found), and [[Cumberland Bone Cave|Cumberland Cave]], Maryland, often in association with the black bear. This suggests a close association with the biome.<ref name=":5" /><ref name="researchgate.net"/> === ''Arctodus simus'' === ==== Paleoecology ==== [[File:Camino_a_paso_de_Cortès._-_panoramio.jpg|thumb|238x238px|[[Woodland|Open woodlands]], such as those in the [[Trans-Mexican Volcanic Belt|Mexican highlands]], would have presented ample foraging opportunities for ''Arctodus''.|left]] Evolving from the smaller ''A. pristinus'' around 1.1 million years ago, scholars today mostly conclude that ''Arctodus simus'' was a colossal, opportunistic [[omnivore]], with a flexible, locally adapted diet akin to the [[brown bear]].<ref name="Figueiridio_et_al_20102"/><ref>{{Cite book |last=Nowak, Ronald M. |title=Walker's mammals of the world |date=1999 |publisher=Johns Hopkins University Press |isbn=0-8018-5789-9 |edition=Sixth |location=Baltimore |oclc=39045218}}</ref><ref name=":302"/><ref name=":156">{{Cite journal |last1=Steffen |first1=Martina L. |last2=Fulton |first2=Tara L. |date=2018-02-01 |title=On the association of giant short-faced bear (Arctodus simus) and brown bear (Ursus arctos) in late Pleistocene North America |journal=Geobios |volume=51 |issue=1 |pages=61–74 |doi=10.1016/j.geobios.2017.12.001}}</ref> If ''Arctodus simus'' wasn't largely herbivorous,<ref name=":53" /><ref name=":132"/> the scavenging of [[megaherbivore]] carcasses, and the occasional predatory kill would have complimented the large amounts of vegetation consumed when available.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/> [[Carbon-13]] ([[Δ13C|''δ''<sup>13</sup>C]]) isotope data gathered from ''Arctodus'' specimens from [[Beringia]], [[California]] and [[Mexico]], indicates that ''Arctodus simus'' had a diet based on [[C3 carbon fixation|C3 resources]]. Preferring closed habitat ([[Woodland|open woodland]] & [[forest]]), ''Arctodus'' consumed [[C3 carbon fixation|C3 vegetation]] ([[Leaf|leaves]], [[Plant stem|stems]], [[fruit]]s, [[Bark (botany)|bark]], and [[flower]]s from trees, shrubs, and cool season [[Poaceae|grasses]]) and the browsers that fed on them, such as [[deer]], [[Camelidae|camelids]], [[Tapirus|tapir]], [[bison]] and [[ground sloth]]s.<ref name="Figueiridio_et_al_20102"/><ref name=":232">{{Cite journal |last1=Trayler |first1=Robin B. |last2=Dundas |first2=Robert G. |last3=Fox-Dobbs |first3=Kena |last4=Van De Water |first4=Peter K. |date=2015-11-01 |title=Inland California during the Pleistocene—Megafaunal stable isotope records reveal new paleoecological and paleoenvironmental insights |url=https://www.sciencedirect.com/science/article/pii/S0031018215004010 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=437 |pages=132–140 |doi=10.1016/j.palaeo.2015.07.034 |bibcode=2015PPP...437..132T |issn=0031-0182}}</ref> Occasionally referred to as the great short-faced bear, ''Arctodus simus'' was particularly plentiful in western [[North America]]. ''Arctodus simus'' was integral to what has been referred to as the ''[[Camelops]]'' fauna, or alternatively ''Camelops''/''[[American mountain deer|Odocoileus lucasi]]'' ("''Navahoceros''") fauna, a faunal province centered in Western North America. The ''Camelops'' fauna was also characterized by [[Euceratherium|shrub-ox]], [[prairie dog]]s, [[Capromeryx|dwarf pronghorns]], [[Nothrotheriops|Shasta ground sloths]], and [[American lion]]s'','' although individual species ranges could shift independently of one another. The diverse flora of the ''Camelops'' faunal province included montane conifers and oak park lands, shrub and grassland that stretched across the [[North American Cordillera]] south of Canada, to the [[Valley of Mexico]]. This supported a variety of large grazing and browsing mammals such as mammoth, horses, bison, mastodon, deer, pronghorns and large ground sloths.<ref>{{Cite journal |last=Pichardo |first=Mario |date=2003 |title=Overview of Central Mexican Prehistory: Morphostratigraphy, Chronostratigraphy, Biostratigraphy |url=https://www.jstor.org/stable/29542453 |journal=Anthropologischer Anzeiger |volume=61 |issue=2 |pages=141–174 |doi=10.1127/anthranz/61/2003/141 |jstor=29542453 |pmid=12872543 |issn=0003-5548}}</ref><ref>{{Cite web |title=KGS--Guidebook 5--Wisconsinan Mammalian Faunas |url=https://www.kgs.ku.edu/Publications/Bulletins/GB5/Martin2/ |access-date=2022-08-01 |website=www.kgs.ku.edu}}</ref><ref name=":9">{{Cite journal |last1=Martin |first1=Larry |last2=Neuner |first2=A. |date=1978-01-01 |title=The End of the Pleistocene in North America |url=https://digitalcommons.unl.edu/tnas/337 |journal=Transactions of the Nebraska Academy of Sciences and Affiliated Societies}}</ref> As ''Arctodus'' has been recovered from a comparatively small number of finds in relation to other large carnivorans, ''Arctodus'' is suggested to have lived in low population densities.<ref name="Pedersen 2728–2736.e82">{{Cite journal |last1=Pedersen |first1=Mikkel Winther |last2=De Sanctis |first2=Bianca |last3=Saremi |first3=Nedda F. |last4=Sikora |first4=Martin |last5=Puckett |first5=Emily E. |last6=Gu |first6=Zhenquan |last7=Moon |first7=Katherine L. |last8=Kapp |first8=Joshua D. |last9=Vinner |first9=Lasse |last10=Vardanyan |first10=Zaruhi |last11=Ardelean |first11=Ciprian F. |date=2021-06-21 |title=Environmental genomics of Late Pleistocene black bears and giant short-faced bears |journal=Current Biology |volume=31 |issue=12 |pages=2728–2736.e8 |doi=10.1016/j.cub.2021.04.027 |pmid=33878301 |hdl-access=free |s2cid=233303447 |hdl=10037/22808}}</ref> Typically thought of as an open habitat specialist, ''Arctodus'' seems to have also been abundant in mixed habitat where [[C3 carbon fixation|C3 vegetation]] was available. Based on the wide distribution of the species, ''Arctodus simus'' inhabited diverse climatic conditions and all sorts of environments, ranging from [[Taiga|boreal forests]] and [[mammoth steppe]] in the north, [[Grassland|open plains]] and [[Montane ecosystems|highland woodlands]] in the interior, [[Subtropics|subtropical]] [[woodland]]s and [[savanna]]s in the south, to the [[Trans-Mexican Volcanic Belt pine–oak forests|pine–oak forests]] of the [[Trans-Mexican Volcanic Belt]], the boundary of the [[Nearctic realm]].<ref name=":352"/><ref name=":02"/><ref name=":102">{{Cite journal |last1=Russell |first1=Dale A. |last2=Rich |first2=Fredrick J. |last3=Schneider |first3=Vincent |last4=Lynch-Stieglitz |first4=Jean |date=May 2009 |title=A warm thermal enclave in the Late Pleistocene of the South-eastern United States |journal=Biological Reviews |volume=84 |issue=2 |pages=173–202 |doi=10.1111/j.1469-185X.2008.00069.x |pmid=19391200 |s2cid=9609391}}</ref><ref name=":132" /><ref name=":410">{{Cite journal |last1=Pérez-Crespo |first1=Víctor Adrián |last2=Arroyo-Cabrales |first2=Joaquín |last3=Morales-Puente |first3=Pedro |last4=Cienfuegos-Alvarado |first4=Edith |last5=Otero |first5=Francisco J. |date=March 2018 |title=Diet and habitat of mesomammals and megamammals from Cedral, San Luis Potosí, México |journal=Geological Magazine |volume=155 |issue=3 |pages=674–684 |bibcode=2018GeoM..155..674P |doi=10.1017/S0016756816000935 |s2cid=132502543}}</ref><ref name=":373">{{Cite journal |last=Eng-Ponce |first=Joaquin |date=August 2021 |title=Reconstruccion paeloambiental del yacimiento La Cinta-Portalitos, Michoacan-Guanajuato, Mexico (thesis) |url=http://bibliotecavirtual.dgb.umich.mx:8083/xmlui/bitstream/handle/DGB_UMICH/6432/FB-M-2021-0909.pdf |journal=Faculty of Biology, Universidad Michoacana de San Nicolás de Hidalgo}}</ref> Preliminary data suggests that certain habitat was optimal for ''Arctodus simus'' populations- the [[pluvial lake]]s, [[Pinyon–juniper woodland|montane forests]] and [[Shrub–steppe|arid sagebrush steppe/grassy plains]] of the inland western USA,<ref>{{Cite journal |last=Grayson |first=Donald K. |date=2006-11-01 |title=The Late Quaternary biogeographic histories of some Great Basin mammals (western USA) |url=https://www.sciencedirect.com/science/article/pii/S0277379106001405 |journal=Quaternary Science Reviews |language=en |volume=25 |issue=21 |pages=2964–2991 |doi=10.1016/j.quascirev.2006.03.004 |bibcode=2006QSRv...25.2964G |issn=0277-3791}}</ref> the [[Montane ecosystems|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], [[Paludification|paludified]] [[mammoth steppe]] in [[Beringia]], and the [[Savanna|mixed savannas]] of the [[Basin and Range Province|south-western USA]] and [[Mexican Plateau]].<ref name=":92" /><ref name=":19" /><ref name=":142">{{Cite journal |last1=Figueirido |first1=Borja |last2=Perez |first2=Alejandro |last3=Schubert |first3=Blaine |last4=Serrano |first4=Francisco |last5=Farrell |first5=Aisling |last6=Pastor |first6=Francisco |last7=Neves |first7=Aline |last8=Romero |first8=Alejandro |date=2017-12-19 |title=Dental caries in the fossil record: A window to the evolution of dietary plasticity in an extinct bear |url=https://www.researchgate.net/publication/321791811 |journal=Scientific Reports |volume=7 |issue=1 |page=17813 |bibcode=2017NatSR...717813F |doi=10.1038/s41598-017-18116-0 |pmc=5736623 |pmid=29259277}}</ref> ==== Competition with ursine bears ==== [[File:Arctodus Simus, Hot Springs, South Dakota.jpg|thumb|''Arctodus simus'' reconstruction at the [[The Mammoth Site|Hot Springs Mammoth Site]], South Dakota.]] Black bears inhabited North America since at least the [[Chibanian|Middle Pleistocene]], whereas [[brown bear]]s, along with [[American lion|lions]], [[bison]] and [[red fox]]es, first emigrated to [[North America]] via [[Beringia]] during the [[Illinoian (stage)|Illinoian Glaciation]] (~170,000 BP).<ref name=":19" /><ref name=":14" /> ''Arctodus simus'' may have been out-competed by [[brown bear]]s as the latter expanded southwards from eastern [[Beringia]], and gradually established itself in [[North America]]. Brown bears and ''Arctodus'' have been reported together in Alaska before ∼34,000 BP, and in later Pleistocene deposits in [[Vancouver Island]], [[Wyoming]] and [[Nevada]]. Although a 2018 study hypothesized that both species did not overlap territorially on Vancouver Island,<ref name=":156"/> a revision of radiocarbon dates by a 2022 study concluded that brown bears, black bears and ''Arctodus simus'' all co-existed on Vancouver Island once the island de-glaciated ~14,500 BP. Noting that all three bears relied on terrestrial resources, the black bears occupied a distinctly lower trophic position in relation to the brown bear, with ''Arctodus'' holding an intermediate position according to a compound‐specific stable isotope analysis. However, this may be an underestimate- an analysis [[Δ15N|''δ''<sup>15</sup>N]] [[threonine]] suggests that protein consumption may be higher in ''Arctodus'' than the other bear species. This may indicate a differentiation in prey choice within the same trophic level (e.g. insects versus terrestrial, plant‐consuming mammals).<ref name=":14" /> The base differences of ''[[Δ13C|δ]]''<sup>[[Δ13C|13]]</sup>[[Δ13C|C]] and [[Δ15N|''δ''<sup>15</sup>N]] values between brown and black bears was narrow, which could be due to the lack of consumption of aquatic resources by the higher trophic level taxa. Although these samples show potential range overlap between species, it is possible that the different taxa were specialized to different environmental settings, which vary greatly across small geographical areas on the mountainous island. The standard differentiation between the more open adapted brown bear and closed forest-adapted black bear is complicated by competition from ''Arctodus simus,'' which seems to have preferred more open habitat.<ref name=":14" /> Additionally, the ''Arctodus'' specimens from Vancouver Island are believed to be female- that modern female brown bears had significant differences in nitrogen-15 values with male brown bears where they co-exist with black bears, and that very large brown bears may not be able to sustain themselves on a vegetarian diet, could indicate size as a constraint on the level of herbivory possible for short‐faced bears. Correspondingly, a sex‐patterned difference in ''δ''<sup>15</sup>N values of bear collagen was observed.<ref name=":14">{{Cite journal |last1=Kubiak |first1=Cara |last2=Grimes |first2=Vaughan |last3=Van Biesen |first3=Geert |last4=Keddie |first4=Grant |last5=Buckley |first5=Mike |last6=Macdonald |first6=Reba |last7=Richards |first7=M. P. |date=2022-06-27 |title=Dietary niche separation of three Late Pleistocene bear species from Vancouver Island, on the Pacific Northwest Coast of North America |url=https://onlinelibrary.wiley.com/doi/10.1002/jqs.3451 |journal=Journal of Quaternary Science |language=en |pages=jqs.3451 |doi=10.1002/jqs.3451 |s2cid=250134103 |issn=0267-8179}}</ref> Meat consumption is confirmed by elevated isotope (''[[Δ13C|δ]]''<sup>[[Δ13C|13]]</sup>[[Δ13C|C]] and [[Δ15N|''δ''<sup>15</sup>N]]) values in numerous [[Beringia]]n [[late Pleistocene]] ''Arctodus simus'' specimens where these bears may have competed for food, but usually occupied a higher [[trophic level]] compared with invading brown bears. For example, inland [[Beringia]]n [[brown bear]]s from the late Pleistocene (exception being to specimens from the [[Yukon]]) consumed [[Embryophyte|terrestrial vegetation]] and [[salmon]] at similar proportions to modern coastal populations, whereas modern inland populations of northern brown bears showed no signatures associated with significant [[salmon]] consumption. In both inland populations of Late Pleistocene Beringian brown bears, reduced signatures of terrestrial meat consumption were noted. On the other hand, data from Beringian specimens of ''Arctodus'' suggest that while omnivorous, only terrestrial sources of meat were important for northern ''Arctodus''.<ref name=":402" /> This contrast is represented in the data- isotopic data from Beringian ''Arctodus'' clusters tightly, and groups differently to Beringian brown bears, although there is overlap.<ref name=":402" /> The forcing of a smaller bear into a more herbivorous diet has been compared to the modern relationship between brown bears and [[American black bear]]s,<ref name=":272" /><ref name=":312">{{Cite journal |last=Bocherens |first=Hervé |date=2015-06-01 |title=Isotopic tracking of large carnivore palaeoecology in the mammoth steppe |url=https://www.sciencedirect.com/science/article/pii/S0277379115001250 |journal=Quaternary Science Reviews |language=en |volume=117 |pages=42–71 |doi=10.1016/j.quascirev.2015.03.018 |bibcode=2015QSRv..117...42B |issn=0277-3791}}</ref> with the black bears often consuming large amounts of salmon and other higher trophic‐level resources in environments where brown bears are rare or absent. Where they overlap, brown bears are observed to take over the higher trophic niche, create avoidance at the population level and seasonally displacing local black bears. Ultimately, black bears tend to have much lower population densities in areas where brown bears are also present. In locations where these two species coexist today, black bears' territorial ranges are much smaller than the ranges of sympatric brown bears.<ref name=":14" /> [[File:Ursus_americanus_PO_04.jpg|thumb|Black bears were much larger in the Pleistocene, and have been found in association with ''Arctodus'' across North America.]] That ''Arctodus simus'' (along with the expansion of [[Mire|peatlands]]) may have excluded brown bears from Eastern Beringia from ∼34,000 to ∼23,000 BP further suggests that ''Arctodus'' may typically have been dominant over brown bears.<ref name=":422">{{Cite journal |last1=Murchie |first1=Tyler J. |last2=Monteath |first2=Alistair J. |last3=Mahony |first3=Matthew E. |last4=Long |first4=George S. |last5=Cocker |first5=Scott |last6=Sadoway |first6=Tara |last7=Karpinski |first7=Emil |last8=Zazula |first8=Grant |last9=MacPhee |first9=Ross D. E. |last10=Froese |first10=Duane |last11=Poinar |first11=Hendrik N. |date=2021-12-08 |title=Collapse of the mammoth-steppe in central Yukon as revealed by ancient environmental DNA |journal=Nature Communications |language=en |volume=12 |issue=1 |pages=7120 |doi=10.1038/s41467-021-27439-6 |pmid=34880234 |pmc=8654998 |bibcode=2021NatCo..12.7120M |issn=2041-1723}}</ref><ref name=":432">{{Cite journal |last1=Barnes |first1=I. |last2=Matheus |first2=P. |last3=Shapiro |first3=B. |last4=Jensen |first4=D. |last5=Cooper |first5=A. |date=2002-03-22 |title=Dynamics of Pleistocene Population Extinctions in Beringian Brown Bears |url=https://www.science.org/doi/10.1126/science.1067814 |journal=Science |language=en |volume=295 |issue=5563 |pages=2267–2270 |doi=10.1126/science.1067814 |pmid=11910112 |bibcode=2002Sci...295.2267B |s2cid=5883943 |issn=0036-8075}}</ref> When ''Arctodus'' went extinct in Beringia ~23,000 BP, [[brown bear]]s recolonised [[Beringia]], but had more carnivorous diets than their [[Beringia]]n kin pre ~34,000 BP. This bolsters the idea that these bears competed for similar resources and niches.<ref name=":19" /><ref name=":156" /> Similarly, while more herbivorous in Beringia while competing with ''Arctodus'', brown bears seem to have been more carnivorous when co-existing with cave bears in [[Eurasia]] (''[[Cave bear|Ursus spelaeus]]'').<ref name=":312" /> Extinction and repopulation is further evidenced by the high genetic (mitochondrial) diversity of Beringian brown bears between 59,000 BP and 10,000 BP (16 haplotypes from 27 samples) in contrast with Beringian ''Arctodus simus'' (7 haplotypes from 23 samples). This contrast in genetic diversity has also been hypothesized to suggest that while brown bears are female [[Philopatry|philopatric]] (i.e. females have a permanent home range), ''Arctodus simus'' may not have been, at least not to the same extent.<ref name=":492">{{Cite journal |last=Bray |first=Sarah C. E. |date=September 2010 |title=Mitochondrial DNA Analysis of the Evolution and Genetic Diversity of Ancient and Extinct Bears |url=https://digital.library.adelaide.edu.au/dspace/bitstream/2440/66285/8/02whole.pdf |journal=School of Environmental and Earth Sciences, University of Adelaide (PHD) |pages=214 (230)}}</ref> On a continent-wide scale, the 2018 study explained that although brown and ''Arctodus simus'' were [[Sympatry|sympatric]] at times as brown bears spread through North America, ''Arctodus simus'' may typically have dominated [[Competition (biology)|competitive]] interactions, particularly when their populations were robust, and displaced brown bears from specific localities. At the end of the Pleistocene one reason [[brown bear]]s persisted where ''Arctodus simus'' went extinct was because ''Arctodus'' may have been less flexible in adapting to new and rapidly changing environments that impacted the availability or quality of food and possibly habitat.<ref name=":156" /> ==== Hibernation ==== [[File:Fall_in_the_Ozarks.jpg|thumb|231x231px|Although [[North America|pan-continental]], ''Arctodus'' specimens have been particularly plentiful from [[Karst|caves]] in the [[Montane ecosystems|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], such as the [[Ozarks]].|left]] According to a 2003 study, in [[Karst|karst regions]], fossils of ''Arctodus simus'' have been recovered almost exclusively from cave sites. In the contiguous United States, 26 of 69 ''Arctodus simus'' sites (~38%) are in caves. That greater than one-third of all sites are caves suggests a close association between this species and cave environments. Furthermore, over 70% of the smaller specimens (once assigned as the ''A. s. simus'' subspecies) are from cave deposits. Not one of the specimens assigned to the larger morph (''A. s. yukonensis'') is from a cave passage. Taking into account the fact that female [[Bear|ursids]] are smaller and more prone to den in caves, it seems logical to conclude that the majority of ''Arctodus simus'' from such deposits were females and may have been denning when they perished.<ref name=":210">{{Cite journal |last1=CHUBERT |first1=BLAINE |last2=KAUFMANN |first2=JAMES |date=2003-08-01 |title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species |url=https://www.researchgate.net/publication/252748398 |journal=Journal of Cave and Karst Studies |volume=65}}</ref> In the [[Americas]], the [[spectacled bear]], [[brown bear]], and [[American black bear|black bear]] use caves for denning when available, and polar bears dig their own "caves" in snow.<ref name=":210" /> Female [[American black bear|black bears]] and [[brown bear]]s in cooler climates enter dens earlier and stay for longer than males. Female [[American black bear|black bears]] and [[brown bear]]s in warmer portions of their range, along with pregnant female [[polar bear]]s, usually den, and often go into [[dormancy]], [[torpor]] and/or maternal denning in winter, while males stay active all year.<ref name=":122">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |bibcode=2010QuInt.217..188S |doi=10.1016/j.quaint.2009.11.010}}</ref> Female specimens of ''Arctodus simus'' have been inferred to have been exhibiting maternal denning, however the expression of metabolic denning ([[hibernation]]/torpor) is unclear in ''Arctodus.''<ref name=":310">{{Cite journal |last1=Fowler |first1=Nicholas L. |last2=Spady |first2=Thomas J. |last3=Wang |first3=Guiming |last4=Leopold |first4=Bruce D. |last5=Belant |first5=Jerrold L. |date=October 2021 |title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51 |issue=4 |pages=465–481 |doi=10.1111/mam.12246 |s2cid=233847639}}</ref> Moreover, to date, there are no records of adults with associated offspring from caves.<ref name=":122" /> However, ''[[Arctotherium|Arctotherium angustidens]]'', a fellow [[Tremarctinae|giant short-faced bear]], has recovered from a cave in [[Argentina]] with offspring.<ref>{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Pomi |first2=Lucas H. |last3=Tonni |first3=Eduardo P. |last4=Rodriguez |first4=Sergio |last5=Dondas |first5=Alejandro |date=2009-09-01 |title=First report of a South American short-faced bears' den (Arctotherium angustidens): palaeobiological and palaeoecological implications |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=33 |issue=3 |pages=211–222 |doi=10.1080/03115510902844418 |issn=0311-5518 |s2cid=55636895|url=http://sedici.unlp.edu.ar/handle/10915/5364 }}</ref> Numerous "bear" beds often preserve ''Arctodus simus'' and both Pleistocene and modern [[American black bear]]s in association (''U.a. amplidens'' and ''U. a. americanus'')- such deposits have been found in [[Missouri]], [[Oklahoma]] and Potter Creek Cave, California, where 8 individuals of ''A. simus'' have been found. These mixed deposits are assumed to have accumulated over time as individual bears (including ''Arctodus'') died during winter sleep.<ref>{{Cite journal |last1=Czaplewski |first1=Nicholas |last2=Rogers |first2=Kyler |last3=Russell |first3=Clayton |date=2018-06-01 |title=Late pleistocene vertebrates from three-forks cave, Adair county, Oklahoma Ozark highland |url=https://www.researchgate.net/publication/324068143 |journal=Journal of Cave and Karst Studies |volume=80 |issue=2 |pages=1–16 |doi=10.4311/2017PA0118 |doi-access=free}}</ref><ref>{{Cite journal |last=Puckette |first=William L. |date=1976 |title=Notes on the occurrence of the short-faced bear (Arctodus) in Oklahoma |url=https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.605.3584&rep=rep1&type=pdf |journal=Proceedings of the Oklahoma Academy of Science |volume=56 |pages=67–68|citeseerx=10.1.1.605.3584 }}</ref><ref>{{Cite journal |last=Feranec |first=Robert S |date=2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |url=https://www.cambridge.org/core/product/identifier/S0033822200034007/type/journal_article |journal=Radiocarbon |language=en |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |issn=0033-8222}}</ref> Furthermore, [[environmental DNA]] suggests that ''Arctodus'' and black bears shared a cave in [[Chiquihuite cave]] in [[Zacatecas]].<ref name="Pedersen 2728–2736.e82" /> At the [[Schell Creek Range|Labor-of-Love cave]] in [[Nevada]], both American black bears and [[brown bear]]s have been found in association with ''Arctodus simus''. A study in 1985 noted that [[sympatry]] between ''Arctodus'' and brown bears preserved in caves is rare, with only [[Converse County, Wyoming|Little Box Elder Cave]] in [[Wyoming]] and Fairbanks II site in [[Alaska]] hosting similar remains.<ref name=":132"/><ref name=":362"/> ==== Paleopathology ==== Beyond dietary dental pathologies present in the genus, the most nearly complete skeleton of ''Arctodus'' preserves extensive pathologies on the skeleton. One hypothesis suggests the [[Fulton County, Indiana|Fulton County]] ''Arctodus'' specimen suffered from a [[syphilis]]-like ([[Treponemal diseases|trepanemal]]) disease, or [[yaws]], based on [[lesion]]s on the [[vertebra]]e, [[ribs]] and both [[ulna]]e.<ref name=":392">{{Cite book |last1=Richards |first1=Ronald L. |url=https://www.biodiversitylibrary.org/bibliography/3480 |title=Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, northern Indiana |last2=Neiburger |first2=Ellis J. |last3=Turnbull |first3=William D. |date=1995 |publisher=Field Museum of Natural History |location=Chicago, Ill.}}</ref><ref>{{Cite book |last1=Rothschild |first1=Bruce M. |url=https://books.google.com/books?id=AGfmCQAAQBAJ&dq=%22arctodus%22+treponemal+infection+rothschild&pg=PA105 |title=Skeletal Impact of Disease: Bulletin 33 |last2=Martin |first2=Larry D. |date=2006 |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref><ref>{{Cite journal |last=Rothschild |first=Bruce M. |date=13 October 1988 |title=Scientific Correspondence |url=https://www.nature.com/articles/335595a0.pdf?origin=ppub |journal=Nature |volume=335 |issue=Existence of syphilis in a Pleistocene bear |pages=595 |doi=10.1038/335595a0 |pmid=3050529 |s2cid=4280184}}</ref> However, alternate hypotheses include [[tuberculosis]], [[osteomyelitis]], [[arthritis]] or a [[fungal infection]], either singularly or in combination with other causes. The same individual records a pathological growth distorting the [[Deltoid muscle|deltoid]] and [[Pectoral muscles|pectoral]] ridges on the right [[humerus]].<ref name=":110"/> Furthermore, [[Dental abscess|abscesses]] are noted between the m1 and m2 of both [[dentaries]], and on [[Abscess|both ulna]]. Hypotheses include syphilis, [[osteoarthritis]], a fungal infection in addition to long term syphilis, or an infected wound.<ref name=":392" /><ref>{{Cite journal |last1=Pinto |first1=A. C. |last2=Etxebarría |first2=F. |date=2001 |title=Description of pathological conditions in the skeleton of an adult male brown bear Ursus arctos from the Cantabrian range of mountains (Reserva Nacional de Caza de Riaño, León) Coruña |url=https://www.udc.es/files/iux/almacen/articulos/cd26_art33.pdf |journal=Cadernos Lab. Xeolóxico de Laxe |volume=2001 |pages=471 |issn=0213-4497}}</ref> == Distribution & habitat == === Map === {{location map+|North America|relief=yes|width=700|float=left|caption=Distribution map of ''Arctodus''<br /> Legend: [[File:Red_pog.svg|8px]] Late Pleistocene ''A. simus'' [[File:Purple 8000ff pog.svg|8px]] Radiocarbon dated ''A.simus'' (<50,000 BP) [[File:Blue_pog.svg|8px]] Early/Middle Pleistocene ([[Irvingtonian]]) ''A.simus'' [[File:Cyan_pog.svg|8px]] ''A. pristinus''|places={{location map~ | North America 2 | label = Friesenhahn Cave | position = none | lat=29.682853 | long=-98.477758 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Bonner Springs (Kansas River) | position = none | lat=39.059722 | long=-94.883611 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Huntington Dam | position = none | lat=39.596595 |long=-111.273836 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Fulton County | position = none | lat=41.0619441 |long=-86.206667|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Sheriden Cave | position = none | lat=40.980733 | long=-83.444783| mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Pellucidar Cave | position = none | lat=50.400278 | long=-126.975833| mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Salt Lake Valley (Silver Creek/Bonneville) | position = none | lat=40.6839 | long=-111.978|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = San Miguel Island (Daisy Cave) | position = none | lat=34.033333 |long=-120.383333|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Saltville Valley | position = none | lat=36.873611 |long=-81.760833|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = La Sena | position = none | lat=40.53325 |long=-100.384545| mark= Purple 8000ff pog.svg }} {{location map~ |North America 2 | label = Gold Run Creek | position = none | lat=63.698261 |long=-138.609632 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Ikpikpuk River | position = none | lat=69.683333 |long= -154.900000 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = La Brea Tar Pits | position = none | lat=34.0628 |long=-118.356|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Lower Hunker Creek | position = none | lat=63.971024 |long= -138.985973 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Three-Forks Cave (Gittin' Down Mountain) | position = none | lat=35.76509 |long=-94.74022|mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Island Ford Cave | position = none | lat=37.786111 | long=-79.988889| mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Sixtymile River | position = none | lat= 63.554796 | long= -139.825129 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Titaluk River | position = none | lat=69.427684 |long=-156.999745 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Ophir Creek | position = none | lat=63.82 |long=-139.34579 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Hester Creek | position = none | lat=63.97 |long=-139.1 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Canyon Creek | position = none | lat=63.82 |long=-139.1 |mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Birch Creek | position = none | lat= 66.255187 | long= -145.835918 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Chiquihuite Cave | position = none | lat= 24.609470 | long= -101.188001 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Eldorado Creek | position = none | lat= 63.91885 | long= -139.31552 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Quartz Creek | position = none | lat= 63.75224 | long= -139.12377 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Natural Trap Cave | position = none | lat=44.973333 | long= -108.193056 | mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Cedral | position = none | lat=23.816667 |long=-100.716667|mark= Red_pog.svg}} {{location map~ |North America 2 | label = La Cinta Portalitos | position = none | lat=20.085833 |long=-101.158611|mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lubbock Lake| position = none | lat=33.621944 | long= -101.889722 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Fern Cave| position = none | lat=34.648933 | long= -86.297864 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cooper River| position = none | lat=33.078822 | long= -79.925568 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cedar Creek (Black Belt, c.f.) | position = none | lat=33.341435 | long= -88.437362 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = The Bar (Central Mississippi Alluvial Valley) | position = none | lat=33.712994 | long= -91.183510 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Clover Bar (Edmonton) | position = none | lat=53.596164 | long= -113.354075 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lebret | position = none | lat=50.757128| long= -103.702833 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = The Mammoth Site | position = none | lat=43.42471 | long= -103.48313 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Frankstown Cave | position = none | lat= 40.450969 | long= -78.337221 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Samwel Cave | position = none | lat= 40.920055 | long= -122.238879 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Potter Creek Cave | position = none | lat= 40.783624 | long= -122.279719 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Alameda Tube | position = none | lat= 37.792099 | long= -122.275258 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Diamond Valley | position = none | lat= 33.678333 | long= -117.041667 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Camp Cady | position = none | lat= 34.941383 | long= -116.609557 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Maricopa Tar Seeps | position = none | lat= 35.061276 | long= -119.392818 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Drews Gap (Lakeview) | position = none | lat= 42.19927 | long= -120.615498 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Fossil Lake | position = none | lat= 43.3258 | long= -120.4909 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Airport Lane | position = none | lat= 45.294329 | long= -118.021097 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Labor-of-Love Cave | position = none | lat= 39.3667 | long= -114.6 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Little Box Elder Cave | position = none | lat= 42.7833 | long= -105.683 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Riverbluff Cave | position = none | lat= 37.106298 | long= -93.32927 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Tequixquiac | position = none | lat= 19.898093 | long= -99.161302 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cueva Quebrada | position = none | lat= 29.711764 | long= -101.387611 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Jinglebob | position = none | lat= 37.2 | long= -100.3 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Bat Cave | position = none | lat= 37.944433 | long= -92.376168 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cowichan Head | position = none | lat= 48.555260 | long= -123.363879 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Moore Pit (Hill Shuler/ Trinity River) | position = none | lat= 32.711180 | long= -96.706766 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Seale Pit (Hill-Shuler/Trinity River) | position = none | lat= 32.773207 | long= -97.010381 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Carroll Cave | position = none | lat= 37.952488 | long= -92.559982 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Keams Canyon | position = none | lat= 35.813586 | long= -110.204220 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Conkling Cavern | position = none | lat= 32.19 | long= -106.585278 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Burnet Cave | position = none | lat= 32.3667 | long= -104.7833 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = U-Bar Cave | position = none | lat= 31.5667 | long= -108.4 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Isleta Caves | position = none | lat= 34.8833 | long= -106.883 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Blacktail Cave | position = none | lat= 47.106583 | long= -112.274182 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Valsequillo | position = none | lat= 18.925262 | long= -98.146481 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lake San Agustin | position = none | lat= 33.924444 | long= -108.227778 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Big Bear site | position = none | lat= 33.466801 | long= -105.793276 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Albuquerque Gravel Pits | position = none | lat= 35.013227 | long= -106.722222 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Bitter Springs Playa | position = none | lat= 36.676633 | long= -111.713866 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Troublesome Creek | position = none | lat= 41.419528 | long= -95.018005 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = American Falls (Cedar Ridge)| position = none | lat= 42.8 | long= -112.9 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Skeleton Cave | position = none | lat= 43.950267 | long= -121.1773 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Pendejo Cave? | position = none | lat= 32.416667 | long= -105.916667 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Round Spring Cave | position = none | lat= 37.281271 | long= -91.412088 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Powder Mill Creek Cave | position = none | lat= 37.193158 | long= -91.171013 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Ester Creek | position = none | lat= 64.848834 | long= -148.071763 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Engineer Creek | position = none | lat= 64.932586 | long= -147.561827 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Goldstream (Fairbanks) | position = none | lat= 64.929919 | long= -147.641979 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cleary Creek | position = none | lat= 65.106979 | long= -147.473061 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Eva Creek Mine | position = none | lat= 64.85 | long= -147.99999 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lilian Creek | position = none | lat= 65.516989 | long= -148.573169 | mark= Red_pog.svg}} {{location map~ |North America 2 | label = Old Crow Flats | position = none | lat=67.441 |long=-139.82|mark= Red_pog.svg}} {{location map~ | North America 2 | label = Cripple Creek | position = none | lat= 64.761387 | long= -147.307813 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = No.2 G-Strip Area, Alaska | position = none | lat= 64.929919 | long= -147.641979 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Big Bear Cave | position = none | lat= 37.927957 | long= -92.168076 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Schultz Cave | position = none | lat= 30.212894 | long= -99.839868 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Fairmead Landfill| position = none | lat=37.061631 | long= -120.194195 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Murrieta (Riverside)| position = none | lat=33.570661 | long= -117.200222 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Irvington| position = none | lat=37.527222 | long= -121.946111 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Vallecito Creek (Anza-Borrego) | position = none | lat=33.024534 | long= -116.209792 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Hay Springs| position = none | lat=42.7 | long= -102.5 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Rock Creek| position = none | lat=34.54173 | long= -101.42989| mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Arkalon | position = none | lat=37.143012 | long= -100.807423 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Doeden Gravel Pit (Yellowstone River) | position = none | lat= 46.4 | long= -105.8 | mark= Blue_pog.svg}} {{location map~ | North America 2 | label = Haile 16A | position = none | lat=29.690000 | long= -82.560000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Sebastian Canal 2 | position = none | lat=27.889646 | long= -80.734793 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Port Charlotte | position = none | lat=26.990278 | long= -82.105833 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Crystal River Power Plant (Inglis 1A & Inglis 1B) | position = none | lat=29.010000 | long= -82.690000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Santa Fe River 1 | position = none | lat=29.840000 | long= -82.700000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Apollo Beach, Leisey Shell Pit 1, Leisey Shell Pit 1A & Leisey Shell Pit 3 | position = none | lat=27.690000 | long= -82.500000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = McLeod Limerock Mine | position = none | lat=29.474891 | long= -82.589610 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Kissimmee 6 | position = none | lat=27.385283 | long= -81.083256 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Bass Point Waterway, Rigby Shell Pit, Venice Beach | position = none | lat=27.099834 | long= -82.460045 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Coleman 2A | position = none | lat=28.760000 | long= -82.050000 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Port Kennedy Cave | position = none | lat=40.10182 | long= -75.42462 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Cumberland Bone Cave | position = none | lat=39.691389 | long= -78.788472 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Ashley River | position = none | lat=32.847008 | long= -80.050759 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Aguascalientes | position = none | lat=21.976449 | long= -102.283105 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Lost World Caverns | position = none | lat=37.8326 | long= -80.4469 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Stout's Ranch (Saw Rock Canyon) | position = none | lat= 37.1 | long= -100.9 | mark= Cyan_pog.svg}} {{location map~ | North America 2 | label = Lake Chapala? | position = none | lat= 20.315517 | long= -103.191921 | mark= Cyan_pog.svg}} {{location map~ |North America 2 | label = Zacoalco | position = none | lat=20.233333 |long=-103.583333|mark= Red_pog.svg}} {{location map~ | North America 2 | label = Rainbow River | position = none | lat=29.083333 | long= -82.416667 | mark= Red_pog.svg}} {{location map~ | North America 2 | label = Lake Rousseau| position = none | lat=29.033333 | long= -82.508333 | mark= Red_pog.svg}} {{location map~ |North America 2 | label = McKittrick Tar Seeps | position = none | lat=35.296314 |long=-119.626014 |mark= Purple 8000ff pog.svg}} {{location map~ |North America 2 | label = Perkins Cave | position = none | lat=38.008889 |long=-92.746389 |mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Cleary (Fairbanks) | position = none | lat= 64.846267 | long= -147.734202 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Upper Cleary River Beds | position = none | lat= 65.076281 | long= -147.427406 | mark= Purple 8000ff pog.svg}} {{location map~ | North America 2 | label = Ester (Fairbanks) | position = none | lat= 64.847823 | long= -147.970072 | mark= Purple 8000ff pog.svg}}}} === Regional Paleoecology === ==== ''Arctodus pristinus'' ==== ===== Eastern North America ===== More fossils of ''Arctodus pristinus'' are known from Florida (about 150) than anywhere else.<ref name=":52">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |s2cid=168164209}}</ref> In the [[Gelasian|Early Pleistocene]] of [[Blancan]] [[Florida]], the [[Santa Fe River (Florida)|Santa Fe River 1 site]] (~2.2 Ma), which ''Arctodus pristinus inabited'', indicated a fairly [[Savanna|open grassland]] environment, dominated by [[Flatwoods|longleaf pine flatwoods]]. [[Karst|Karst sinks]] and [[Spring (hydrology)|springs]] were present, very much like modern [[Florida]]. ''Arctodus pristinus'' would have co-existed with megafauna such as terror birds (''[[Titanis]])'', sabertooth cats (''[[Xenosmilus]]''), giant sloth (''[[Eremotherium]]'', ''[[Paramylodon]]'', ''[[Megalonyx]]''), giant armadillos (''[[Holmesina]]'', ''[[Glyptotherium]], [[Pachyarmatherium]]''), [[gomphothere]]s (''[[Rhynchotherium]]'' (''[[Cuvieronius|?Cuvieronius?]]'')), hyenas (''[[Chasmaporthetes|Chasmoporthetes]]''), canids (''[[Borophagus]]'', ''[[Canis lepophagus]]''), peccary (''[[Platygonus]]''), llama (''[[Hemiauchenia]]''), antilocaprids (''[[Capromeryx]]''), and three-toed horse (''[[Nannippus]]''). Smaller fauna included [[condor]]s, [[Rail (bird)|rails]] and [[duck]]s among other small birds, rodents such as [[Erethizon|porcupines]], lizards, snakes, alligators, turtles, and arthropods.<ref>{{Cite journal |last1=Gould |first1=G.C. |last2=Quitmyer |first2=Irvy |date=2005-01-01 |title=Titanis walleri: Bones of contention |url=https://www.researchgate.net/publication/288892560 |journal=Bulletin of the Florida Museum of Natural History |volume=45 |pages=201–229}}</ref><ref>{{Cite journal |last1=MacFadden |first1=Bruce |last2=Labs-Hochstein |first2=Joann |last3=Hulbert |first3=Richard |last4=Baskin |first4=Jon |date=2007-02-01 |title=Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange |url=https://www.researchgate.net/publication/249521166 |journal=Geology |volume=35 |issue=2 |page=123 |bibcode=2007Geo....35..123M |doi=10.1130/G23186A.1}}</ref> The evolution of ''Arctodus simus'', competition with ''[[Tremarctos floridanus]]'' and [[American black bear|black bears]] (both of which only appear in [[Florida]] in the [[Late Pleistocene]]),<ref name=":52" /> and possibly the transitioning of [[Pleistocene]] [[Florida]] from a hot, wet, densely forested habitat to a still hot, but drier and much more open biome are thought to be factors behind the gradual disappearance of ''Arctodus pristinus'' in the [[Chibanian|Middle Pleistocene]] (300,000 BP).<ref name=":02"/><ref name=":92"/> ==== ''Arctodus simus'' ==== ===== Mexico ===== Tremarctine bears were dominant in Mexico during the Late Pleistocene, with ''Arctodus simus'' and ''[[Tremarctos floridanus]]'' being plentiful.<ref name=":92"/> ''Arctodus simus'' was limited to the Mexican plateau, which was generally occupied by tropical thorn scrub and scrub woodland.<ref name=":372">{{Cite journal |last=Eng-Ponce |first=Joaquin |date=August 2021 |title=Reconstruccion paeloambiental del yacimiento La Cinta-Portalitos, Michoacan-Guanajuato, Mexico (thesis) |url=http://bibliotecavirtual.dgb.umich.mx:8083/xmlui/bitstream/handle/DGB_UMICH/6432/FB-M-2021-0909.pdf |journal=Faculty of Biology, Universidad Michoacana de San Nicolás de Hidalgo}}</ref><ref name=":472">{{Cite journal |last1=University of Geneva, Switzerland |last2=Ray |first2=N. |last3=Adams |first3=J.M. |date=2001 |title=A GIS-based Vegetation Map of the World at the Last Glacial Maximum (25,000-15,000 BP) |url=http://intarch.ac.uk/journal/issue11/rayadams_index.html |journal=Internet Archaeology |issue=11 |doi=10.11141/ia.11.2}}</ref> An ''Arctodus simus'' individual from [[Cedral, San Luis Potosí|Cedral]], [[San Luis Potosí]], inhabited closed vegetation, based on the individual's [[Δ13C|''δ''<sup>13</sup>C]] signature. Consuming C3 resources, its' diet may have incorporated contemporaneous C3 specialists such as [[tapir]], [[Hemiauchenia|llamas]], [[Camelops|camels]], and [[Nothrotheriops|Shasta ground sloth]]'','' likely along with browsed vegetation. Fauna which visited closed areas at Cedral include ''[[Paramylodon]]'', [[Platygonus|peccaries]], some horses, [[mastodon]], and occasionally ''[[Glyptotherium]]'', ''[[Megalonyx]]'', bison, [[Dire wolf|dire wolves]], [[American lion]]s and [[Columbian mammoth|Colombian mammoths]]. The site, incorporating trees, herbs and cacti, hosted an open [[gallery forest]] near to [[Savanna|grassland]] or [[Shrubland|scrub]] with a [[Humid subtropical climate|humid climate]]. This [[Savanna|forest-savanna mosaic]], supporting a diverse mammalian herbivore and carnivore fauna, was part of the wider [[Mesic habitat|mesic]] savanna and [[Pinyon–juniper woodland|piñon–juniper woodland]] ecoregion which ''Arctodus'' inhabited in the [[Late Pleistocene]] [[Mexican Plateau|central Mexico]] and [[Southwestern United States|southwestern USA]].<ref name=":410"/><ref>{{Cite book |last=Harris |first=Arthur |url=https://www.researchgate.net/publication/265165536 |title=Pleistocene Vertebrates of Southwestern USA and Northwestern Mexico |date=2014-08-30}}</ref><ref>{{Cite journal |last=Harris |first=Arthur H. |title=Reconstruction of Mid Wisconsin Environments in Southern New Mexico |url=https://www.wipp.energy.gov/library/cra/2009_cra/references/Others/Harris_1987_Reconstruction_of_Mid_Wisconsin_Environments.pdf |journal=National Geographic Research}}</ref> At [[Lake Cuitzeo|La Cinta-Portalitos]] ([[Michoacán]]/[[Guanajuato]]) in the Trans-Mexican Volcanic Belt, prime habitat for ''Arctodus simus'' was the closed temperate forests of the [[Madrean pine–oak woodlands]], dominated by [[pine]]s, [[oak]]s, [[hornbeam]]s, and ferns (''[[Polypodium]]'' & ''[[Pecluma]]''). Associated fauna primarily found in this habitat include [[Allen's cotton rat|''Sigmodon'']], ''[[Aztlanolagus]]'', [[ocelot]]s, [[gray fox]], ''Hemiauchenia'', pronghorns ([[Capromeryx minor|''Capromeryx'']], ''[[Stockoceros]]'', ''[[Tetrameryx]]''), [[cottontail rabbit]]s, [[bobcat]]s, ground sloths (''Nothrotheriops'', ''Megalonyx)'', ''[[Smilodon|Smilodon fatalis]]'' and ''Panthera atrox''. Today, these high-humidity forests are found between 2500-2800m altitude- however, in the Late Pleistocene, they were found at less than 2000m altitude. ''Tremarctos floridanus'' at this locality, on the other hand, inhabited [[gallery forest]]s and their wetlands, along with [[white-tailed deer]], [[Neochoerus aesopi|capybaras]], ''[[Pampatherium]]'', [[Equus (genus)|horses]], and ''[[Cuvieronius]]''.<ref name=":372" /> Similar highland ''Arctodus simus'' remains have been recovered from [[Zacoalco de Torres|Zacoalco]], [[Hueyatlaco|Valsequillo]], and [[Tequixquiac]].<ref>{{Cite journal |last=Lucas |first=Spencer G. |date=January 2008 |title=Late Pleistocene Vertebrate Fossil Assemblages From Jalisco, Mexico |url=https://www.researchgate.net/publication/281862788 |journal=Neogene Mammals. New Mexico Museum of Natural History and Science |volume=Bulletin 44 |pages=51–64 |via=ResearchGate}}</ref><ref>{{Cite journal |last=Hibbard |first=Claude W. |date=18 February 1955 |title=Pleistocene Vertebrates from the Upper Becerra (Becerra Superior) Formation, Valley of Tequixquiac, Mexico, with Notes on Other Pleistocene Forms |journal=Contributions from the Museum of Paleontology |volume=XII |issue=5 |pages=47–96 |hdl=2027.42/48290 |url=http://deepblue.lib.umich.edu/handle/2027.42/48290 |language=en-US}}</ref> ===== Western USA ===== [[File:North_Slope_Santa_Ynez_Mtns.jpg|thumb|''Arctodus simus'' inhabited Californian savannas for over a million years.]] With over 50% (22/38) of specimens found in the contiguous United States from the terminal Pleistocene (<40,000 BP), the Western USA was highly productive habitat for ''Arctodus simus''.<ref name=":92" /> In particular, the [[Pacific Mountain System]] seems to represent a cradle of evolution for ''Arctodus simus''. The earliest finds of ''Arctodus simus'' are from California, from early and middle [[Irvingtonian]] age sites such as [[Vallecito Creek (California)|Vallecito Creek]], Irvington, Riverside, and Fairmead.<ref name=":46" /><ref>{{Cite journal |last=Cassiliano |first=Michael L. |date=1999 |title=Biostratigraphy of Blancan and Irvingtonian Mammals in the Fish Creek-Vallecito Creek Section, Southern California, and a Review of the Blancan-Irvingtonian Boundary |url=https://www.jstor.org/stable/4523978 |journal=Journal of Vertebrate Paleontology |volume=19 |issue=1 |pages=169–186 |doi=10.1080/02724634.1999.10011131 |jstor=4523978 |issn=0272-4634}}</ref><ref>{{Cite book |last=Firby |first=Jean Brower |url=https://books.google.com/books?id=qOdKAQAAMAAJ |title=Revision of the Middle Pleistocene Irvington Fauna of California |date=1968 |publisher=University of California |language=en}}</ref><ref>{{Cite book |last1=Dundas |first1=Robert G. |last2=Chatters |first2=James C. |date=2013-01-01 |chapter=The mid-Irvingtonian Fairmead Landfill fossil site, Madera County Paleontology Collection, and Fossil Discovery Center of Madera County, California |editor=Keith Putirka |title=Geologic Excursions from Fresno, California, and the Central Valley |pages=63–78 |publisher=Geological Society of America |language=en |doi=10.1130/2013.0032(04)|isbn=978-0-8137-0032-8 }}</ref> Evidence from Inland California suggests that despite the shift to aridified environments from the Early to Late Pleistocene of California (1.1Ma to ~15,000 BP), ''Arctodus simus'' remained consistent with the consumption of C3 resources. This period saw the evolution from wetter mixed woodland-grassland and marsh/prairie C3 dominated environs at Irvington and Fairmead, to the more arid, mixed C3-C4 savannas of the McKittrick Tar Pits. Whereas [[jaguar]]s, ''[[Homotherium]]'', ''[[American cheetah|Miracinonyx]]'' and ''Smilodon'' ultimately transitioned to ''Panthera atrox'' and [[coyote]]s in the local predator guild, only dire wolves and ''Arctodus simus'' remained ever present. Foraging opportunities would have been plentiful for ''Arctodus'', with grasses, [[Chenopodioideae|chenopods]], ''[[Xanthium]]'', [[Typhaceae|cattails]], [[Cyperaceae|sedges]], [[willow]], [[oak]], [[spruce]], [[juniper]], and [[Artemisia (plant)|sagebrush]] at Fairmead, and [[pine]]s, [[juniper]], [[Atriplex|saltbush]], [[Arctostaphylos|manzanita]], and [[Echinocystis|wild cucumber]] at McKittrick.<ref name=":232" /> To what extent ''Arctodus'' fed on this vegetation, versus consuming generalists and specialized browsers such as deer ([[Elk|''Cervus'']] & ''[[Odocoileus]]''), camelids (''Hemiauchenia'' & ''Camelops''), ''Paramylodon'', and [[Platygonus|peccaries]] can be clued from the [[La Brea Tar Pits]]. Microwear and general wear patterns on the teeth of recovered from ''Arctodus'' specimens are most similar to the herbivorous spectacled bear, and suggest that they avoided hard/brittle foods, and had a more specialized diet than black bears recovered from the same site. Should ''Arctodus'' have also been a predator, competition with closed habitat, browser specialists would have included ''Smilodon'' and ''Panthera atrox'' in Late Pleistocene inland California.<ref name=":232" /><ref>{{Cite journal |last=Feranec |first=Robert S |date=November 2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |url=https://www.researchgate.net/publication/255728816 |journal=Radiocarbon |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |via=ResearchGate}}</ref><ref>{{Cite journal |last1=Springer |first1=Kathleen |last2=Scott |first2=Eric |last3=Murray |first3=Lyndon K. |last4=Sagebiel |first4=James |date=2009 |title=The Diamond Valley Lake local fauna: late Pleistocene vertebrates from inland southern California |editor=Albright, L. B. III |journal=Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne |url=https://www.academia.edu/218818}}</ref> Many more finds come from across California, and Oregon,<ref>{{Cite web |last=Yumpu.com |title=LATE PLEISTOCENE AIRPORT LANE FOSSIL SITE, LA GRANDE ... |url=https://www.yumpu.com/en/document/view/12116022/late-pleistocene-airport-lane-fossil-site-la-grande- |access-date=2022-07-17 |website=yumpu.com |language=en}}</ref><ref>{{Cite journal |last1=Van Tassell |first1=Jay |last2=Rinehart |first2=John |last3=Mahrt |first3=Laura |date=June 2014 |title=Late Pleistocene Airport Lane fossil site, La Grande, northeast Oregon |url=https://www.oregongeology.org/pubs/OG/OGv70n01_print.pdf |journal=Oregon Geology |volume=70 |issue=1 |pages=3–13 |via=Oregon Department of Geology and Mineral Studies}}</ref><ref>{{Cite web |title=The Spokesman-Review - Google News Archive Search |url=https://news.google.com/newspapers?nid=1314&dat=19280626&id=PGpWAAAAIBAJ&sjid=vvMDAAAAIBAJ&pg=5453,5034598 |access-date=2022-07-20 |website=news.google.com}}</ref> where the semi-arid woodland/scrub transitioned to [[Forest steppe|forest-steppe]].<ref name=":472" />[[File:Paleontological_landscape_painting,_White_Sands_National_Park,_United_States.jpg|thumb|A reconstruction of Rancholabrean New Mexico ([[White Sands National Park|White Sands]]).|left]]The [[Intermontane Plateaus|Intermontane Plateau]], which largely hosted subalpine parkland,<ref name=":472" /> had the highest number of ''Arctodus simus'' specimens south of the ice sheets. The region has yielded some of the largest specimens of ''A. simus,'' including, what was once the largest specimen on record, from Bonneville, Utah.<ref>{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |url=https://www.jstor.org/stable/3628418 |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 |issn=0022-8443}}</ref> In contrast with other parts of North America, the plateau received more rainfall during the Late Pleistocene, because glacially cooled air collided with hot desert air, resulting in increased precipitation and cool cloudy conditions. As a result, this greatly expanded the range of woodlands where desert exists today, with [[pluvial lake]]s being abundant in the south-west. The mid-[[Wisconsin glaciation|Wisconsian]] U-Bar cave (New Mexico) was populated by fauna typically found in cooler and more mesic habitats, particularly habitats characterized by a notable pulse of cool-season precipitation, relatively warm winters, and limited warm-season moisture. [[Artemisia tridentata|Sagebrush]], grasses, and woodland vegetation suggests cooler summers and a more pronounced emphasis on cool-season precipitation than in lowland New Mexico (Dry Cave). This more xeric and warmer climate contrasts with the sagebrush steppe-woodland of the Last Glacial Maximum. Notable fauna which lived alongside ''Arctodus simus'' included Shasta ground sloth, [[Euceratherium|shrub-ox]], pronghorns (''Stockoceros,'' ''Capromeryx''), ''Camelops'', ''Odocoileus'', horses, ''Lynx'', [[Cougar|puma]], black bear, [[Oreamnos|mountain goats]]'','' prairie dogs, and [[Stock's vampire bat]].<ref>{{Cite journal |last=Harris |first=Arthur H. |date=November 1985 |title=Preliminary report 0n the vertebrate fauna of U-Bar Gave, Hidalgo County, New Mexico |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/7/n4/nmg_v7_n4_p74.pdf |journal=New Mexico Geology |pages=74–84}}</ref><ref>{{Cite web |title=U-Bar Cave |url=https://www.utep.edu/leb/pleistnm/sites/ubarcave.htm |access-date=2022-07-24 |website=www.utep.edu}}</ref> Dire wolves were also found in association with ''Arctodus simus'' at U-Bar cave, along with Conkling Cavern- both species are the most common carnivorans of Rancholabrean New Mexico.<ref>{{Cite book |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=S--oDQAAQBAJ&dq=Rock+Creek+texas+arctodus&pg=PA296 |title=Vertebrate Paleontology in New Mexico: Bulletin 68 |last2=Sullivan |first2=Robert M. |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref> Beyond New Mexico,<ref>{{Cite journal |last1=Schultz |first1=C. Bertrand |last2=Howard |first2=Edgar B. |last3=Schultz |first3=C. Bernard |date=1935 |title=The Fauna of Burnet Cave, Guadalupe Mountains, New Mexico |url=https://www.jstor.org/stable/4064215 |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=87 |pages=273–298 |jstor=4064215 |issn=0097-3157}}</ref><ref>{{Cite journal |last=Harris |first=Arthur H. |date=1993 |title=Quaternary Vertebrates of New Mexico |url=https://www.utep.edu/leb/curators/QuatVert.pdf |journal=Vertebrate Paleontology in New Mexico, New Mexico Museum of Natural History and Science |volume=Bulletin 2 |pages=179–197}}</ref><ref>{{Cite journal |last1=Harris |first1=A. H. |last2=Findley |first2=J. S. |date=1964-01-01 |title=Pleistocene-Recent fauna of the Isleta caves, Bernalillo County, New Mexico |url=http://www.ajsonline.org/cgi/doi/10.2475/ajs.262.1.114 |journal=American Journal of Science |language=en |volume=262 |issue=1 |pages=114–120 |doi=10.2475/ajs.262.1.114 |bibcode=1964AmJS..262..114H |issn=0002-9599}}</ref><ref>{{Cite conference |last1=Morgan |first1=Gary S. |last2=Lucas |first2=Spencer G. |last3=Love |first3=David |date=2009 |title=Cenozoic vertebrates from Socorro County, central New Mexico |editor=Virgil Lueth |editor2=Spencer G. Lucas |editor3=Richard M. Chamberlin |book-title=New Mexico Geological Society Fall Field Conference Guidebook: 60 Geology of the Chupadera Mesa |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/60/60_p0321_p0336.pdf |pages=321–336}}</ref><ref>{{Cite journal |last=Morgan |first=Gary S. |last2=Lucs |first2=Spencer G. |date=2005-01-01 |title=Pleistocene vertebrates from southeastern New Mexico |url=https://digitalcommons.usf.edu/kip_articles/4347 |journal=KIP Articles}}</ref> other important specimens have also been found in Arizona, Idaho, Montana,<ref>{{Cite journal |last=Hill |first=Christopher L. |date=2006-01-01 |title=Stratigraphic and geochronologic contexts of mammoth (Mammuthus) and other Pleistocene fauna, Upper Missouri Basin (northern Great Plains and Rocky Mountains), U.S.A. |url=https://www.sciencedirect.com/science/article/pii/S104061820500056X |journal=Quaternary International |series=Third International Mammoth Conference, Dawson, Yukon |language=en |volume=142-143 |pages=87–106 |doi=10.1016/j.quaint.2005.03.007 |bibcode=2006QuInt.142...87H |issn=1040-6182}}</ref> Nevada,<ref>{{Cite journal |last1=Emslie |first1=Steven D. |last2=Mead |first2=Jim I. |date=August 2020 |title=The Age and Vertebrate Paleontology of Labor-of-Love Cave, White Pine County, Nevada |url=https://bioone.org/journals/western-north-american-naturalist/volume-80/issue-3/064.080.0301/The-Age-and-Vertebrate-Paleontology-of-Labor-of-Love-Cave/10.3398/064.080.0301.full |journal=Western North American Naturalist |volume=80 |issue=3 |pages=277–291 |doi=10.3398/064.080.0301 |s2cid=225958789 |issn=1527-0904}}</ref> and Utah. The Intermontane Plateau extended deep into Mexico, where it demarked the southernmost habitat of ''Arctodus simus''.[[File:Canis_dirus_3484.jpg|thumb|Dire wolves are often found at the same localities as ''Arctodus simus'', and were the most common predator of western North America.]]Comparatively, the [[Rocky Mountain System]] had the fewest number of specimens of ''Arctodus simus'' in western North America. However, one of the youngest dated ''Arctodus simus'' is from a cave near Huntington Reservoir, Utah, which sits at an elevation of 2,740m (~9,000&nbsp;ft),. The central and southern Rocky Mountains may have acted as refugia for ''Arctodus simus'', in addition to other contemporary high-elevation alpine fauna such as Colombian mammoths, [[mastodon]], [[Equus conversidens|horses]], and [[Bison latifrons|giant bison]] ≤11,400 BP (10,000 <sup>14</sup>C BP).<ref name=":382" /><ref name=":9" /><ref name=":442">{{Cite journal |last=Stuart |first=Anthony John |date=May 2015 |title=Late Quaternary megafaunal extinctions on the continents: a short review: LATE QUATERNARY MEGAFAUNAL EXTINCTIONS |url=https://onlinelibrary.wiley.com/doi/10.1002/gj.2633 |journal=Geological Journal |language=en |volume=50 |issue=3 |pages=338–363 |doi=10.1002/gj.2633|s2cid=128868400 }}</ref> Other remains have been found from [[Natural Trap Cave]] and Little Box Elder Cave in Wyoming,<ref>{{Cite journal |last=Long |first=C. A. |date=1971 |title=Significance of the Late Pleistocene fauna from the Little Box Elder Cave, Wyoming, to studies of zoogeography of recent mammals |url=https://www.semanticscholar.org/paper/Significance-of-the-Late-Pleistocene-fauna-from-the-Long/f20528d15f55b41a3f6487726c65698286febf4b |s2cid=55933331 |language=en}}</ref> and Montana.<ref>{{Cite journal |last1=Smith |first1=Larry N. |last2=Hill |first2=Christopher L. |last3=Reiten |first3=Jon |title=Quaternary and Late Tertiary of Montana: Climate, Glaciation, Stratigraphy, and Vertebrate Fossils |url=https://mbmg.mtech.edu/pdf/geologyvolume/Smith_QuaternaryMontanaFinal.pdf |journal=Montana Bureau of Mines and Geology Publication 122 |volume=1: Geologic History |via=Montana Bureau of Mines and Geology}}</ref> ===== Interior USA ===== The [[Interior Plains]] were composed of temperate steppe grassland,<ref name=":472" /> and among the specimens yielded from this region is the largest ''Arctodus simus'' currently on record, from the banks of the Kansas river. The [[Irvingtonian]] age Doeden gravel pits in Montana preserves an open grassland habitat, with riparian woodlands, and likely some shrublands.<ref>{{Cite web |title=Abstract: PLEISTOCENE VERTEBRATES FROM THE DOEDEN LOCAL FAUNA (ILLINOIAN/SANGAMONIAN?), YELLOWSTONE RIVER VALLEY, EASTERN MONTANA (Rocky Mountain - 55th Annual Meeting (May 7-9, 2003)) |url=https://gsa.confex.com/gsa/2003RM/webprogram/Paper53111.html |access-date=2022-07-20 |website=gsa.confex.com}}</ref> ''Arctodus simus'' co-existed with ground sloths (''Megalonyx'', ''Paramylodon''), Pacific mastodon, [[Camelops|camels]], and oxen (''[[Bootherium]]'').<ref>{{Cite journal |last1=McDonald |first1=Andrew T. |last2=Atwater |first2=Amy L. |last3=Dooley Jr |first3=Alton C. |last4=Hohman |first4=Charlotte J.H. |date=2020-11-16 |title=The easternmost occurrence of Mammut pacificus (Proboscidea: Mammutidae), based on a partial skull from eastern Montana, USA |journal=PeerJ |volume=8 |pages=e10030 |doi=10.7717/peerj.10030 |issn=2167-8359 |pmc=7676352 |pmid=33240588}}</ref><ref>{{Cite journal |last1=Hill |first1=Christopher L |last2=Wilson |first2=Michael C |date=2002 |title=Fossil Arctodus from the Doeden Local Fauna (Illinoian/Sangamonian?), Eastern Montana |url=https://www.researchgate.net/publication/270216214 |journal=Unknown |via=ResearchGate}}</ref><ref name=":4">{{Cite journal |last1=Hill |first1=Christopher L. |last2=Wilson |first2=Mike C. |date=2000 |title=The Doeden Local Fauna (Illinoian/Sangamonian?), Eastern Montana |url=https://www.researchgate.net/publication/270216333 |journal=Unknown |pages=140–142 |via=ResearchGate}}</ref> As bison were yet to migrate into North America, Colombian mammoths and horses dominated these Sangamonian grasslands.<ref>{{Cite journal |last1=Froese |first1=Duane |last2=Stiller |first2=Mathias |last3=Heintzman |first3=Peter D. |last4=Reyes |first4=Alberto V. |last5=Zazula |first5=Grant D. |last6=Soares |first6=André E. R. |last7=Meyer |first7=Matthias |last8=Hall |first8=Elizabeth |last9=Jensen |first9=Britta J. L. |last10=Arnold |first10=Lee J. |last11=MacPhee |first11=Ross D. E. |date=2017-03-28 |title=Fossil and genomic evidence constrains the timing of bison arrival in North America |journal=Proceedings of the National Academy of Sciences |language=en |volume=114 |issue=13 |pages=3457–3462 |doi=10.1073/pnas.1620754114 |issn=0027-8424 |pmc=5380047 |pmid=28289222|bibcode=2017PNAS..114.3457F |doi-access=free }}</ref> Additional [[Irvingtonian]] remains have been recovered from Arkalon in Kansas, Hay Springs in Nebraska, and Rock Creek in Texas.[[File:Wildflowers_on_ranchland,_State_Highway_965,_Llano_County,_Texas,_USA_(13_April_2012).jpg|thumb|221x221px|''Arctodus'' also roamed the southern mixed grasslands of Texas.|left]]Whereas the northern plains aridified into cold steppe in the [[Rancholabrean]] age (e.g. [[The Mammoth Site|Mammoth site]], South Dakota),<ref name=":242">{{Cite journal |last=Louguet-Lefebvre |first=Sophie |date=2013-12-15 |title=The Columbian mammoths from the Upper Pleistocene of Hot Springs (South Dakota, United States) |url=https://journals.openedition.org/paleo/2861 |journal=PALEO. Revue d'archéologie préhistorique |language=en |issue=24 |pages=149–171 |doi=10.4000/paleo.2861 |issn=1145-3370}}</ref> the southern plains were a parkland with riparian deciduous forests (e.g. [[Celtis|hackberry]]), and large expanses of mixed grass prairie grasslands grading into wet meadows. At [[Lubbock Lake Landmark|Lubbock Lake]] on the [[Llano Estacado]], Texas, above freezing/mild winters and cool summers highlighted a regional climate of reduced seasonality and stable humidity in the latest Pleistocene.<ref name=":252">{{Cite journal |last=Johnson |first=Eileen |date=1986 |title=Late Pleistocene and Early Holocene Vertebrates and Paleoenvironments on the Southern High Plains, U.S.A. |url=https://www.erudit.org/en/journals/gpq/1900-v1-n1-gpq1924/032647ar.pdf |journal=Géographie physique et Quaternaire |volume=40 |issue=3 |pages=249–261|doi=10.7202/032647ar }}</ref> Overall, ''Arctodus simus'', grey wolves and coyotes were part of a predator guild throughout the Rancholabrean great plains, and were joined by Colombian mammoths, camels, ''Hemiauchenia'', and American pronghorns. In the northern plains, woolly mammoths also ranged across the steppe, whereas in the south, ''Smilodon'', dire wolves, grey fox and red fox in the south preyed upon horses prairie dogs, horses (''Equus'' & ''[[Haringtonhippus]]''), peccaries, ''Odocoileus'', ''Capromeryx'', ''Bison antiquus'' and ''Holmesina''.<ref name=":242" /><ref name=":252" /> Beyond Texas,<ref>{{Cite journal |last=Smith |first=Felisa A. |last2=Tomé |first2=Catalina P. |last3=Elliott Smith |first3=Emma A. |last4=Lyons |first4=S. Kathleen |last5=Newsome |first5=Seth D. |last6=Stafford |first6=Thomas W. |date=February 2016 |title=Unraveling the consequences of the terminal Pleistocene megafauna extinction on mammal community assembly |url=https://onlinelibrary.wiley.com/doi/10.1111/ecog.01779 |journal=Ecography |language=en |volume=39 |issue=2 |pages=223–239 |doi=10.1111/ecog.01779 |issn=0906-7590}}</ref> ''Arctodus'' has also been found from the Kaw River and [[Meade County, Kansas|Jinglebob]] in Kansas.<ref>{{Cite journal |last=Taylor |first=D. W. |date=1960 |title=Late Cenozoic molluscan faunas from the High Plains |url=https://pubs.er.usgs.gov/publication/pp337 |journal=Professional Paper |doi=10.3133/pp337 |issn=2330-7102}}</ref> In the lowlands in the eastern Interior plains, the plains transitioned to closed habitat. At the terminal Pleistocene [[Sheriden Cave]], Ohio, a mosaic habitat consisting of marsh, open woodland, and patchy grassland was home to ''Arctodus simus'', ''[[Cervalces scotti]]'', caribou, peccaries ([[Platygonus compressus|''Platygonus'']], [[Long-nosed peccary|''Mylohyus'']]), [[Castoroides|giant beaver]], [[North American porcupine|porcupine]], and [[American marten|American pine marten]].<ref name=":282">{{Cite journal |last=Tankersley |first=Kenneth B. |date=26 May 1997 |title=Sheriden: A Clovis cave site in eastern North America |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1520-6548(199709)12:6%3C713::AID-GEA9%3E3.0.CO;2-1 |journal=Geoarchaeology|volume=12 |issue=6 |pages=713–724|doi=10.1002/(SICI)1520-6548(199709)12:6<713::AID-GEA9>3.0.CO;2-1 }}</ref><ref name=":322">{{Cite journal |last1=Redmond |first1=Brian G. |last2=Tankersley |first2=Kenneth B. |date=10 February 2005 |title=Evidence of Early Paleoindian Bone Modification and Use at the Sheriden Cave Site (33WY252), Wyandot County, Ohio |url=https://www.cambridge.org/core/product/identifier/S0002731600039020/type/journal_article |journal=American Antiquity |language=en |volume=70 |issue=3 |pages=503–526 |doi=10.2307/40035311 |jstor=40035311 |s2cid=162034505 |issn=0002-7316}}</ref> Similar remains have been found in Indiana and Iowa.<ref>{{Cite web |title=Giant Short-Faced Bear {{!}} University of Iowa Museum of Natural History - The University of Iowa |url=https://mnh.uiowa.edu/giant-short-faced-bear |access-date=2022-07-18 |website=mnh.uiowa.edu |language=en}}</ref> To the south, the [[Interior Highlands]] had a very high density of ''Arctodus simus'' specimens (second only to the black bear),<ref name=":92" /> due to the high rate of preservation in the cave-rich region. Sympatry between the two species is most apparent in Missouri- ''Arctodus simus'' has been found in association with black bears at Riverbluff, Bat and Big Bear caves.<ref>{{Cite journal |last=Hawksley |first=Oscar |date=July 1965 |title=Short-Faced Bear (Arctodus) Fossils from Ozark Caves |url=https://caves.org/pub/journal/NSS%20Bulletin/vol%2027%20part%203.pdf |journal=Bulletin of the National Speleological Society |volume=27 |issue=3 |pages=77–92}}</ref> At [[Riverbluff Cave]], the most abundant claw marks are from ''Arctodus simus''. Some being up to 4 meters high on the cave walls, they are most abundant at the bear beds and their associated passageways, indicating a close relationship with denning. Other impressions found include claw marks from a large cat (either ''Panthera atrox'' or ''Smilodon fatalis'') and ''Platygonus'' trackways.<ref name=":1" /> Big Bear Cave preserves fossilized hair associated with ''Arctodus''.<ref name=":210" /> During the Last Glacial Maximum, both bears were joined by dire wolves, coyotes, jaguars, [[snowshoe hare]], [[groundhog]]s and [[beaver]]s at Bat Cave, which also records thousands of ''Platygonus'' remains. These fauna inhabited well-watered forest-grassland ecotone with a strong taiga influence. These open woodlands were dominated by [[pine]]s and [[spruce]], and to a lesser extent by [[oak]]s''.''<ref>{{Cite journal |last=Woodruff |first=Aaron L. |date=2016 |title=Description, Taphonomy, and Paleoecology of the Late Pleistocene Peccaries (Artiodactyla: Tayassuidae) from Bat Cave, Pulaski County, Missouri |url=https://dc.etsu.edu/cgi/viewcontent.cgi?article=4444&context=etd |journal=Department of Geosciences, East Tennessee State University |issue=Paper 3051 |via=East Tennessee State University Digital Commons @ East Tennessee State University}}</ref><ref>{{Cite journal |last1=Woodruff |first1=Aaron L. |last2=Schubert |first2=Blaine W. |date=2019-07-04 |title=Seasonal denning behavior and population dynamics of the late Pleistocene peccary Platygonus compressus (Artiodactyla: Tayassuidae) from Bat Cave, Missouri |journal=PeerJ |volume=7 |pages=e7161 |doi=10.7717/peerj.7161 |issn=2167-8359 |pmc=6612422 |pmid=31308997}}</ref><ref>{{Cite journal |last1=Hawksley |first1=Oscar |last2=Reynolds |first2=Jack F. |last3=Foley |first3=Robert F. |date=July 1973 |title=Pleistocene Vertebrate Fauna of Bat Cave, Pulaski County, Missouri |url=https://caves.org/pub/journal/NSS%20Bulletin/Vol%2035%20num%203.pdf |journal=Bulletin of the National Speleological Society |volume=35 |issue=3 |pages=61–87}}</ref><ref>{{Cite journal |last=Santucci |first=Vincent L. |last2=Kenworthy |first2=Jason |last3=Kerbo |first3=Ron |date=2022-01-18 |title=An inventory of paleontological resources associated with national park service caves |url=https://digitalcommons.usf.edu/kip_articles/271 |journal=KIP Articles}}</ref> However, evidence from Riverbluff Cave suggests that the region occasionally cycled through drier, grassier periods in the last 55,000 years.<ref>{{Cite web |last1=Smith |first1=Matthew D |last2=Dorale |first2=Jeffrey A |last3=Johnson |first3=Aaron W |last4=Forir |first4=Matthew D |date=2013 |title=A speleothem record of paleoenvironmental change from Riverbluff Cave, Missouri, U.S.A |url=https://iro.uiowa.edu/esploro/outputs/abstract/A-speleothem-record-of-paleoenvironmental-change/9984240795902771 |access-date=2022-07-26 |website=iro.uiowa.edu}}</ref>[[File:Mountain-type_Woodland_Caribou.jpg|thumb|Open boreal woodlands provided adequate resources for ''Arctodus simus''.]] ===== Eastern USA ===== Compared to other regions, ''Arctodus simus'' was relatively rare in eastern North America.<ref name=":92" /> To the north, the [[Appalachian Highlands]] were dominated by taiga.<ref name=":472" /> Post-LGM [[Saltville (archaeological site)|Saltville]], Virginia, was a mosaic of grassy/herb laden open areas intermixed with open canopy [[Taiga|boreal woodlands]] (oaks, pines, spruce, birch, firs) and marshes. Inhabiting in this [[C3 carbon fixation|C3]] resource dominated environment were ''Arctodus simus'', mastodon, (southernmost) [[woolly mammoth]]s, oxen (''Bootherium),'' horses, caribou, ground sloths (''Megalonyx''), dire wolves, beavers, ''[[Cervalces]]'', and a variety of warm-adapted reptiles, suggesting that a more mesic and less seasonal climate allowed for the mixing of more typically northern and southern fauna. Heavy bone damage on a mammoth carcass by both dire wolves and ''Arctodus'' suggests a potentially competitive scavenging relationship <ref>{{Cite journal |last=Simpson |first=Emily |date=2019-05-01 |title=Paleoecology and Land-Use of Quaternary Megafauna from Saltville, Virginia |url=https://dc.etsu.edu/etd/3590 |journal=Electronic Theses and Dissertations}}</ref><ref name=":332">{{Cite journal |last1=Schubert |first1=Blaine W. |last2=Wallace |first2=Steven C. |date=August 2009 |title=Late Pleistocene giant short-faced bears, mammoths, and large carcass scavenging in the Saltville Valley of Virginia, USA |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.2009.00090.x |journal=Boreas |language=en |volume=38 |issue=3 |pages=482–492 |doi=10.1111/j.1502-3885.2009.00090.x |s2cid=129612660}}</ref> Additional remains have been found at Island Ford Cave in Virginia, and [[Frankstown Township, Blair County, Pennsylvania|Frankstown]] in Pennsylvania. [[File:Lake Rousseau.JPG|thumb|222x222px|[[Lake Rousseau]], Florida, is the south-eastern most locality which ''Arctodus simus'' is known to have inhabited.|left]] To the south, the [[Atlantic Plain]]s covered a great expanse of lowland, from the open deciduous woodlands of the [[Atlantic coastal plain|Atlantic coast]], to the semi-arid woodland/scrub of Florida, to the spruce-fir conifer forests and open habitat of the [[Gulf Coastal Plain]]. Although scarce, this contrast of habitats highlights the adaptability of ''Arctodus simus''. At the [[Rainbow River]] and [[Lake Rousseau]] localities in Rancholabrean Florida, three ''Arctodus simus'' specimens have been recovered, alongside ''Smilodon'', dire wolves, jaguars, ground sloths (''Paramylodon'', ''Megalonyx''), llamas (''[[Palaeolama]]'', ''Hemiauchenia''), [[Tapirus veroensis|Vero's tapir]], giant beaver, [[capybara]], ''Holmesina'', horses, ''Bison antiquus'', mastodon, Colombian mammoths and ''Tremarctos floridanus'', in a climate similar to today's. That one of the three individuals was a very large, older specimen establishes extreme sexual dimorphism as the explanation behind size differences in ''Arctodus simus''. Furthermore, the abundance of black bears, and particularly Florida short faced bears in Florida, has led to a theorized niche partitioning of ursids in Florida, with ''Tremarctos floridanus'' being herbivorous, and black bears and ''Arctodus simus'' being omnivorous, with ''Arctodus'' being possibly more inclined towards carnivory.<ref name=":02" /> In the [[Black Belt (geological formation)|Black Belt]] of Late Pleistocene [[Mississippi]], a terrestrial [[floodplain]] at [[Trinity, Mississippi|Cedar Creek]] hosted a mixture of grassland and mixed woodlands adapted species (including ''Arctodus simus''). Horses, then bison, are the most numerous of the fauna, but were also joined by Colombian mammoths, coyotes, ''[[Dasypus bellus]]'' and ''Holmesina'' on the plains. Mastodon, ground sloths (''Eremotherium'', ''Megalonyx''), peccaries (''Platygonus'', ''Mylohylus''), deer ([[Elk|''Cervus'']], ''[[White-tailed deer|Odocoileus]]''), lynx, black bear, Florida short-faced bear, [[margay]]s, [[gray fox]], ''Hemiauchenia,'' turkeys and racoons in the open woodlands, with giant beavers, lesser beavers, and capybara inhabiting the marshes. Coyotes and black bears from this locality are unusually small for the Late Pleistocene. Further west, in the [[Mississippi Alluvial Plain (ecoregion)|Mississippi Alluvial Plain]], the fauna ''Arctodus simus'' encountered at [[Lake Whittington|the Bar]], [[Arkansas]] was similar to Saltville, Virginia, with the addition of ''Paleolama'', ''Bison'', ''Mylohyus'', black bears, tapirs, [[manatee]]s and [[alligator snapping turtle]]s. During the Last Glacial Maximum, in part due to glacial meltwaters producing a cold microclimate, boreal forests extended from [[40th parallel north|40° N]] to coastal regions near [[23rd parallel north|23° N]]. Mississippi's boreal forests were dominated by pine, spruce, ash, aspen, oak and hickory, with more deciduous trees and herbs/grasses in the lowlands. However, the presence of the giant tortoise, ''[[Hesperotestudo|Hesperotestudo crassiscutata]]'', in both localities is indicative of mild winters, and limited seasonality.<ref>{{Cite journal |last1=Baghai-Riding |first1=Nina L. |last2=Husley |first2=Danielle B. |last3=Beck |first3=Christine |last4=Blackwell |first4=Eric |date=December 2017 |title=Late Pleistocene Megafauna from Mississippi Alluvium Plain Gravel Bars |url=https://paludicolavertpaleo.files.wordpress.com/2019/11/11-3-baghai-riding-2017.pdf |journal=Paludicola |volume=11 |issue=3 |pages=124–147 |via=Rochester Institute of Vertebrate Paleontology}}</ref><ref>{{Cite journal |last=Ruddell |first=Michael W. |date=December 1999 |title=Quaternary Vertebrate Paleoecology of the Central Mississippi Alluvial Valley; Implications for the Initial Human Occupation |url=https://trace.tennessee.edu/cgi/viewcontent.cgi?article=3184&context=utk_graddiss |journal=Tennessee Research and Creative Exchange |via=University of Tennessee, Knoxville}}</ref><ref>{{Cite journal |last1=Kurtén |first1=Björn |last2=Kaye |first2=John M. |date=March 1982 |title=Late Quaternary Carnivora from the Black Belt, Mississippi |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.1982.tb00519.x |journal=Boreas |language=en |volume=11 |issue=1 |pages=47–52 |doi=10.1111/j.1502-3885.1982.tb00519.x}}</ref><ref>{{Cite journal |last=Kaye |first=John Morgan |date=1974 |title=Pleistocene Sediment and V ocene Sediment and Vertebrate Fossil Associations in the ossil Associations in the Mississippi Black Belt: a Genetic Approach |url=https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=3611&context=gradschool_disstheses |journal=LSU Historical Dissertations and Theses. |volume=2612 |via=Louisiana State University}}</ref> ''Arctodus'', along with Colombian mammoths, seems to have avoided the coastal savannas of the south east, where ''[[Mixotoxodon]]'' was present. Additional finds of south-eastern ''Arctodus simus'' are from Alabama,<ref>{{Cite journal |last1=Ebersole |first1=Jun A. |last2=Ebersole |first2=Sandy M. |date=December 2011 |title=Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Taxa |url=http://almnh.museums.ua.edu/wp-content/uploads/sites/2/2018/12/BALMNH_No_28_2011.pdf |journal=Alabama Museum of Natural History Bulletin |volume=28 |pages=24–25 |via=University of Alabama}}</ref> South Carolina.<ref>{{Cite web |last=apmiller@postandcourier.com |first=Andrew Miller |title=SC diver finds rare prehistoric bear tooth fossil in Cooper River |url=https://www.postandcourier.com/news/sc-diver-finds-rare-prehistoric-bear-tooth-fossil-in-cooper-river/article_c8cf9104-8d7a-11eb-bd4d-af15386d585a.html |access-date=2022-07-09 |website=Post and Courier |language=en}}</ref><ref>{{Cite web |date=2021-04-08 |title=First Record of the Giant Short-Faced Bear (Arctodus simus) in South Carolina |url=https://markgelbart.wordpress.com/2021/04/08/first-record-of-the-giant-short-faced-bear-arctodus-simus-in-south-carolina/ |access-date=2022-07-09 |website=GeorgiaBeforePeople |language=en}}</ref> and Texas.<ref name=":13" /><ref>{{Cite journal |last=Slaughter |first=Bob H. |date=1966 |title=The Moore Pit Local Fauna; Pleistocene of Texas |url=https://www.jstor.org/stable/1301775 |journal=Journal of Paleontology |volume=40 |issue=1 |pages=78–91 |jstor=1301775 |issn=0022-3360}}</ref> ===== Canada ===== [[File:Vashon_Glaciation_Mockup_2016-06-26.png|thumb|On the boundary of the northern glacier.|left]] The vast majority of Canada was glaciated during the Late Pleistocene. However, southern [[Alberta]] may have been spared, providing a tundra ecosystem (at least until the Last Glacial Maximum).<ref>{{Cite journal |last1=Young |first1=Robert R. |last2=Burns |first2=James A. |last3=Smith |first3=Derald G. |last4=Arnold |first4=L. David |last5=Rains |first5=R. Bruce |date=1994-08-01 |title=A single, late Wisconsin, Laurentide glaciation, Edmonton area and southwestern Alberta 2.3.CO;2 |journal=Geology |volume=22 |issue=8 |pages=683–686 |doi=10.1130/0091-7613(1994)022<0683:ASLWLG>2.3.CO;2 |issn=0091-7613}}</ref> ''Arctodus simus'' remains have been recovered from the mid-[[Wisconsin glaciation|Wisconsian]] (~22,000 BP) near Edmonton, forming a predator guild with the gray wolf and American lion. Also present were ''Megalonyx'', horses (''E. conversidens'' & ''E. niobrarensis''), [[Barren-ground caribou|caribou]], [[Camelops|camels]], mammoths (Colombian and woolly), mastodon, bison (''B. priscus'' & ''B. latifrons''), and oxen (''Ovibos'' & ''Bootherium''). The higher diversity of grazers to browsers suggested a more open environment- that the American lion individual was noticeably smaller than its southern contemporaries contrasts with the huge ''Arctodus'' and large wolf specimens.<ref name=":62">{{Cite journal |last1=Burns |first1=James A. |last2=Young |first2=Robert R. |date=1994-02-01 |title=Pleistocene mammals of the Edmonton area, Alberta. Part I. The carnivores |url=http://www.nrcresearchpress.com/doi/10.1139/e94-036 |journal=Canadian Journal of Earth Sciences |language=en |volume=31 |issue=2 |pages=393–400 |doi=10.1139/e94-036 |bibcode=1994CaJES..31..393B |issn=0008-4077}}</ref> The entry to the ice-free corridor to Beringia may have also been near [[Edmonton]], providing a migration pathway to Beringia. ''Arctodus'' remains from similar habitat has also been recovered from Saskatchewan,<ref>{{Cite journal |last=Harington |first=C. R. |date=1973 |title=A Short-Faced Bear From Ice Age Deposits at Lebret, Saskatchewan |url=https://bluejayjournal.ca/index.php/bluejay/article/view/4039 |journal=Blue Jay |language=en |volume=31 |issue=1 |doi=10.29173/bluejay4039 |s2cid=222373512 |issn=2562-5667}}</ref> and from the [[Forest steppe|forest-steppe]] of Late Pleistocene Vancouver Island.<ref name=":156"/><ref>{{Cite journal |last1=Steffen |first1=Martina L. SteffenM L. |last2=Harington |first2=C. R. HaringtonC R. |date=2010-07-23 |title=Giant short-faced bear (Arctodus simus) from late Wisconsinan deposits at Cowichan Head, Vancouver Island, British Columbia |url=https://cdnsciencepub.com/doi/10.1139/E10-018 |journal=Canadian Journal of Earth Sciences |volume=47 |issue=8 |pages=1029–1036 |language=en |doi=10.1139/E10-018|bibcode=2010CaJES..47.1029S }}</ref> ''Arctodus'' was a scarce member of the Pleistocene fauna of southern Canada- extant herbivorous bears are browsers, not grazers, so the scarcity of ''Arctodus'' in mid-latitude North America may be due to a lack of suitable vegetation on the steppe. On the other hand, should ''Arctodus simus'' have been a large and strict carnivore, perhaps ''Arctodus simus'' would never have been very numerous in an open ecosystem.<ref name=":62" /> ===== Beringia ===== [[File:Wolf_with_Caribou_Hindquarter.jpg|thumb|230x230px|''Arctodus'' is suggested to have had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|Beringian wolves]], akin to modern [[Wolf|wolves]] and [[brown bear]]s.]] Mostly isolated by the Cordilleran and Laurentide ice sheets, Beringia is considered ecologically separate to the rest of North America, being largely an extension of the Eurasian [[mammoth steppe]].<ref>{{Citation |last1=David Webb |first1=S. |title=Vertebrate paleontology |date=2003 |url=https://linkinghub.elsevier.com/retrieve/pii/S157108660301025X |work=Developments in Quaternary Sciences |volume=1 |pages=519–538 |publisher=Elsevier |language=en |doi=10.1016/s1571-0866(03)01025-x |isbn=978-0-444-51470-7 |access-date=2022-06-28 |last2=Graham |first2=Russell W. |last3=Barnosky |first3=Anthony D. |last4=Bell |first4=Christopher J. |last5=Franz |first5=Richard |last6=Hadly |first6=Elizabeth A. |last7=Lundelius |first7=Ernest L. |last8=Gregory McDonald |first8=H. |last9=Martin |first9=Robert A.}}</ref> However, due to the occasional opening of an ice-free corridor, and the migration barrier of the Beringian gap, meant that Eastern Beringia ([[Alaska]] and the [[Yukon]]) supported a unique assemblage of fauna, with many endemic North American fauna flourishing (such as ''Arctodus simus'') within a mostly Beringian ecosystem.<ref>{{Cite journal |last1=Churcher |first1=C. S. |last2=Morgan |first2=A. V. |last3=Carter |first3=L. D. |date=2011-02-08 |title=Arctodus simus from the Alaskan Arctic Slope |url=https://cdnsciencepub.com/doi/10.1139/e93-084 |journal=Canadian Journal of Earth Sciences |volume=30 |issue=5 |pages=1007–1013 |language=en |doi=10.1139/e93-084}}</ref> This mostly open and treeless steppe-tundra, dominated by grasses, sedges, ''Artemisia spp.'', and a range of other forbs had a cold, dry climate, which prevented glaciation. Currently, all specimens of ''Arctodus'' in [[Beringia]] have been dated to a 27,000 year window (50,000 BP~23,000 BP) from Eastern Beringia.<ref name=":19" /><ref name=":156"/> However, additional undated remains may be of [[Sangamonian]] age.<ref>{{Cite journal |last=Harington |first=C. R. |date=1980 |title=Radiocarbon Dates on Some Quaternary Mammals and Artifacts from Northern North America |url=https://www.jstor.org/stable/40509084 |journal=Arctic |volume=33 |issue=4 |pages=815–832 |doi=10.14430/arctic2598 |jstor=40509084 |issn=0004-0843}}</ref> The [[Alaska North Slope|North Slope]] of Alaska <40,000 BP (Ikpikpuk and Titaluk rivers) preserves an upland and floodplain environment, with horses, bison then caribou being the most populous herbivores, and woolly mammoths, muskoxen, elk and [[saiga antelope]] more scarce. Cave lions, bears (''Ursus arctos'' and ''Arctodus simus''), and Beringian wolves made up the megafaunal predator guild.<ref name="sciencedirect.com">{{Cite journal |last1=Mann |first1=Daniel H. |last2=Groves |first2=Pamela |last3=Kunz |first3=Michael L. |last4=Reanier |first4=Richard E. |last5=Gaglioti |first5=Benjamin V. |date=2013-06-15 |title=Ice-age megafauna in Arctic Alaska: extinction, invasion, survival |url=https://www.sciencedirect.com/science/article/pii/S0277379113001200 |journal=Quaternary Science Reviews |language=en |volume=70 |pages=91–108 |doi=10.1016/j.quascirev.2013.03.015 |bibcode=2013QSRv...70...91M |issn=0277-3791}}</ref><ref>{{Cite journal |last1=Monteath |first1=Alistair J. |last2=Gaglioti |first2=Benjamin V. |last3=Edwards |first3=Mary E. |last4=Froese |first4=Duane |date=2021-12-28 |title=Late Pleistocene shrub expansion preceded megafauna turnover and extinctions in eastern Beringia |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=52 |pages=e2107977118 |doi=10.1073/pnas.2107977118 |issn=0027-8424 |pmc=8719869 |pmid=34930836}}</ref> That caribou and [[muskox]] utilized the warmer, wetter portions of the regional vegetation mosaic (similar to the moist acidic tundra vegetation which dominates today), while horse, bison, and mammoth were dryland specialists,<ref name="sciencedirect.com"/> may reflect the preferred habitat of ''Arctodus'', as isotope data suggests caribou and muskox were principal components of the carnivorous portion of Beringian ''Arctodus simus''<nowiki/>' diet.<ref name=":312"/> Additionally, upon the flooding of the [[Bering Strait]] and [[Paludification|expansion]] of [[Mire|peatlands]] in Eastern Beringia during [[MIS 3|MIS-3]], [[Panthera spelaea|lions]], [[brown bear]]s and ''[[Homotherium]]'' went regionally extinct ~35,000 BP, whereas ''Arctodus'' persisted. Simultaneously, [[muskox]], [[bison]], non-caballine horses (''[[Haringtonhippus]]'') and other megafaunal herbivores in Beringia experienced population bottlenecks in MIS-3, whilst [[Woolly mammoth|mammoth]] populations steadily declined. This restriction of prey and habitat could explain the extinctions. However, genetically distinct ''[[Panthera spelaea]]'' and brown bears appear in [[MIS 2|MIS-2]] circa the extinction of ''Arctodus'' in a re-emerged Beringia ~23,000 BP (possibly due to sharp climatic cooling associated with [[Heinrich event|Heinrich Event-2]]), opening up the possibility that some level of competition was at play.<ref name=":19" /><ref name=":312"/><ref name=":422"/><ref name=":432"/> The idea that ''Arctodus'' had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|wolves]] and ''[[Homotherium]]'' in Beringia has been explored,<ref name=":312"/> and with the additional possibility that ''Arctodus'' restricted brown bears and ''Homotherium'' access to [[Reindeer|caribou]] pre-[[Last Glacial Maximum|LGM]].<ref name=":412">{{Cite journal |last1=Fox-Dobbs |first1=Kena |last2=Leonard |first2=Jennifer A. |last3=Koch |first3=Paul L. |date=2008-04-24 |title=Pleistocene megafauna from eastern Beringia: Paleoecological and paleoenvironmental interpretations of stable carbon and nitrogen isotope and radiocarbon records |url=https://www.sciencedirect.com/science/article/pii/S0031018208000266 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=261 |issue=1 |pages=30–46 |doi=10.1016/j.palaeo.2007.12.011 |bibcode=2008PPP...261...30F |issn=0031-0182}}</ref> Not only did ''Arctodus'' likely compete at a higher [[trophic level]] than the majority of brown bears in Beringia, ''Arctodus''<nowiki/>' [[Nitrogen 15|nitrogen-15]] levels are higher in the Yukon, suggesting that ''Arctodus'' possibly occupied an even higher trophic level there relative to other ''Arctodus'' in Beringia. However, isotope differences more likely reflect subtle differences in the isotopic composition of primary producers in the region.<ref name=":402"/><ref>{{Cite journal |last1=Lanoë |first1=François B. |last2=Reuther |first2=Joshua D. |last3=Holmes |first3=Charles E. |last4=Hodgins |first4=Gregory W. L. |date=2017-11-01 |title=Human paleoecological integration in subarctic eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0277379117300999 |journal=Quaternary Science Reviews |language=en |volume=175 |pages=85–96 |doi=10.1016/j.quascirev.2017.10.003 |bibcode=2017QSRv..175...85L |issn=0277-3791}}</ref> It would be reasonable to assume that meat and bone marrow were likely to be the primary food resources for some northern populations of ''A. simus'', in which the survival during the cold season could have depended on the regular scavenging of [[ungulate]] carcasses, as is the case with [[Kodiak bear|Alaskan brown bears]].<ref name="Figueiridio_et_al_20102"/> Ultimately, an opportunistic foraging strategy including up to 50% vegetation, and the meat of reindeer, muskox, [[carrion]], and possibly some predators, is consistent with the isotopic data and the conclusions of the ecomorphological studies.<ref name=":312"/> == Discussions regarding diet == === "Super predator" hypothesis === [[File:DSC09100_-_Extinct_Bear_(37221999825).jpg|thumb|Skeletal reconstruction of ''Arctodus simus''.]] One past proposal, suggested by [[Björn Kurtén]], envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed the [[megafauna]] of the Pleistocene with its great physical strength.<ref name=":162"/> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":212">{{Cite book |last=E. |first=Matheus, Paul |title=Locomotor adaptations and ecomorphology of short-faced bears (Arctodus simus) in eastern Beringia |date=2003 |publisher=Yukon Palaeontologist, Gov't. of Yukon |oclc=243520303}}</ref><ref name=":222">{{Cite book |last=Randally |first=Lynch, Eric |title=Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics |date=2012-08-06 |publisher=East Tennessee State University |oclc=818344518}}</ref> significantly more [[Gracility|gracile]] so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":202">{{Cite journal |last1=SOIBELZON |first1=LEOPOLDO H. |last2=SCHUBERT |first2=BLAINE W. |date=2011 |title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears |journal=Journal of Paleontology |volume=85 |issue=1 |pages=69–75 |doi=10.1666/10-037.1 |jstor=23019499 |s2cid=129585554}}</ref> Due to their long legs, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. Correspondingly, although a 700''&nbsp;''kg ''Arctodus'' may have been able to reach a maximum speed of {{Convert|51|km/h|mph}}, all modern bears have maximum speeds significantly lower than mass based calculations for speed- such speeds would have likely exceeded skeletal strength with their bulk. As a result, paleontologist Paul Matheus suggests that ''Arctodus''<nowiki/>' top speed was {{Convert|40-45|km/h|mph|abbr=on}}. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/> Moreover, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/> However, analysis of the forelimb of ''Arctodus'' suggests the bear could have been in the early stages of [[cursorial]] evolution- ''A. simus'' was somewhat more prone to [[Cursorial|cursorial tendencies]], being capable of more efficient locomotion, ''A. simus'' was interpreted as capable of high-speed (relative to extant bears), straight-line locomotion, and was likely more adept at pursuing large prey than the extant [[Polar bear|polar]] and [[brown bear]]s.<ref name=":222" /> However, that the limbs are elongated in the proximal rather than distal limb segments, had a plantigrade gait, and a stride which had little to no unsupported intervals, put doubt to this theory.<ref name=":132"/> Moreover, the pronation of the forearm and the flexion of the wrist and digits, and more lightly muscled forelimbs, all of which are crucial to grasping a large prey animal with the forepaws, were probably less powerful in ''Arctodus'' than in either the [[brown bear]] or in ''[[Panthera]].''<ref name=":110" /> Ultimately, the lack of specialized predatory adaptions (such as the absence of [[Canine tooth|laterally compressed canines]], and [[carnassial]]s built for crushing and grinding rather than shearing meat) puts doubt to any species-wide [[Hypercarnivore|hyper-carnivorous]] interpretations of ''Arctodus.''<ref name="Figueiridio_et_al_20102" /><ref name="Meloro 133–1462">{{Cite journal |last1=Meloro |first1=Carlo |last2=de Oliveira |first2=Alessandro Marques |date=2019-03-01 |title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf |journal=Journal of Mammalian Evolution |volume=26 |issue=1 |pages=133–146 |doi=10.1007/s10914-017-9413-x |s2cid=25839635}}</ref><ref name=":110" /> Although the only extant [[Hypercarnivore|hyper-carnivorous]] [[Bear|ursid]], the [[polar bear]], also lacks [[Carnassial|carnassial shears]], the species' primary subsistence on [[blubber]] rather than coarser flesh may negate the need to evolve dentition specialised in processing meat (the [[Polar bear|polar bear's]] recent evolution notwithstanding).<ref name=":132" /><ref name=":110" /> === Specialist kleptoparasite vs Omnivore === [[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|[[American mastodon]] arm bone with ''A.&nbsp;simus'' tooth marks at the [[Denver Museum of Nature & Science]] in [[Denver]], [[Colorado]]]] [[File:Shortfacedbear-1070375.jpg|thumb|226x226px|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of [[Molar (tooth)|molar]] damage associated with processing bone, [[Tooth decay|dental cavities]], and the lack of specialisation in the [[Canine tooth|canines]], discourages a [[Hypercarnivore|hyper-carnivorous]] interpretation of ''Arctodus''.]] ''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref> This idea was challenged by a comprehensive review by paleontologist Borja Figueirido and colleagues in 2010,<ref name="Figueiridio_et_al_20102" /> a 2013 study of the micro-wear of the teeth of various extant and extinct bears (examining ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]]), and a 2015 study focusing on [[carnivora]]ns recovered from [[Rancho La Brea]].<ref name="Donohue2">{{cite journal |author1=Donohue, Shelly L. |author2=DeSantis, Larisa R. G. |author3=Schubert, Blaine W. |author4=Ungar, Peter S. |year=2013 |title=Was the giant short-faced bear a hyper-scavenger? A new approach to the dietary study of ursids using dental microwear textures |journal=PLOS ONE |volume=8 |issue=10 |page=e77531 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name=":172">{{Cite journal |last1=DeSantis |first1=Larisa |last2=Schubert |first2=Blaine |last3=Schmitt-Linville |first3=Elizabeth |last4=Ungar |first4=Peter |last5=Donohue |first5=Shelly |last6=Haupt |first6=Ryan |date=2015-01-01 |title=Dental Microwear Textures of Carnivorans from the La Brea Tar Pits, California, and Potential Extinction Implications |url=https://www.researchgate.net/publication/282253545 |journal=La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas |pages=37–52}}</ref> Specialized scavengers like [[hyena]]s show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from [[La Brea Tar Pits|Rancho La Brea]], researchers concluded that ''Arctodus simus'' was not a specialized scavenger. Of living bears, this population of ''A. simus'' showed the most similar tooth wear patterns to its closest living relative, the [[spectacled bear]], which can have a highly varied diet- from obligate omnivory to, on the most part, being almost purely herbivorous in diet.<ref name=":132" /> However, this depends on the region, and seasonal availability.<ref name="Donohue2"/> Additionally, the higher rates of tooth breakage at La Brea were revisited, and due to a relative lack of bone related microwear on other carnivorans (even lower than the modern day) was attributed to the hunting of larger prey, and the acquisition and/or defense of kills.<ref name=":172" /> Moreover, severe tooth crown fractures and alveolar infections were found in the South American giant short faced bear ([[Arctotherium|''Arctotherium'' ''angustidens'']]). These were interpreted as evidence of feeding on tough materials (e.g. bones), which could tentatively indicate for these bears the regular scavenging of ungulate carcasses obtained through [[kleptoparasitism]]. However, such dental pathologies were not observed in the specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_20102" /> Additionally, the short, broad [[Rostrum (anatomy)|rostrum]] of ''Arctodus'' is a characteristic also shared with the [[sun bear]] and the [[spectacled bear]], which are both [[Omnivore|omnivorous]].<ref name="Figueiridio_et_al_20102" /> Moreover, isotope analyses of Beringian ''Arctodus'' specimens suggest that ''Arctodus'' had a low consumption rate of horses and mammoths in Beringia, despite those species making up ~50% of the available biomass in Beringia.<ref name=":312"/> Furthermore, the relative lack of ''Arctodus'' remains at [[predator trap]]s such as the [[La Brea Tar Pits|La Brea tar pits]], suggests that ''Arctodus'' did not compete for carcasses.<ref name=":142"/> Although [[La Brea Tar Pits|La Brea]] has produced more ''Arctodus simus'' specimens than any other site (presumably due to the quality of preservation with tar), they are only 1% of all carnivorans in the pits,<ref name=":172" /> which is a similar rate to [[brown bear]]s and [[American black bear|black bears]], both omnivorous [[Bear|ursids]] which lean towards herbivory.<ref>{{Cite journal |last1=McHorse |first1=Brianna K. |last2=Orcutt |first2=John D. |last3=Davis |first3=Edward B. |date=2012-04-15 |title=The carnivoran fauna of Rancho La Brea: Average or aberrant? |url=https://www.sciencedirect.com/science/article/pii/S0031018212000958 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=329-330 |pages=118–123 |doi=10.1016/j.palaeo.2012.02.022 |bibcode=2012PPP...329..118M |issn=0031-0182}}</ref> As only two specimens were located from the [[Natural Trap Cave]] in [[Wyoming]] by 1993, a similar rate (~0.9%) of relative abundance was calculated for ''Arctodus'' compared to other [[megafauna]] at the site.<ref>{{Cite journal |last1=Wang |first1=Xiaoming |last2=Martin |first2=Larry |date=1993-01-01 |title=Late Pleistocene, paleoecology and large mammal taphonomy, Natural Trap Cave, Wyoming |url=https://www.researchgate.net/publication/267156684 |journal=National Geographic Research & Exploration |volume=9 |pages=422–435}}</ref> Dental pathologies which have been found, such as [[incisor]] wear & [[Calculus (dental)|supragingival dental calculus]] in a young individual,<ref name=":210"/> and [[Tooth decay|cavities]] associated with [[carbohydrate]] consumption in individuals from [[La Brea Tar Pits|La Brea]], further suggest an omnivorous diet for ''Arctodus simus''.<ref name=":142" /> Further evidence comes from the evolution of brain size relative to body size- ursids which do not exhibit dormancy and have a high caloric diet, showed a weak but significant correlation with bigger relative brain size. ''Arctodus simus'' plotted in between the likely hypercarnivorous ''[[Cephalogale]],'' and the obligately herbivorous Eurasian cave bear and ''[[Indarctos]],'' suggesting omnivory.<ref>{{Cite journal |last=Veitschegger |first=Kristof |date=2017-06-05 |title=The effect of body size evolution and ecology on encephalization in cave bears and extant relatives |journal=BMC Evolutionary Biology |volume=17 |issue=1 |pages=124 |doi=10.1186/s12862-017-0976-1 |issn=1471-2148 |pmc=5460516 |pmid=28583080}}</ref> ==== Comparisons with modern fauna ==== [[File:Brown_bear_(Ursus_arctos_arctos)_running.jpg|thumb|Significant parallels can be found with the once contemporary [[brown bear]] (''Ursus arctos'') and [[hyena]]s.]] The most commonly accepted ecological parallels of ''Arctodus simus'' in scientific literature are the [[brown bear]] and the [[spectacled bear]].<ref name="Figueiridio_et_al_20102" /><ref name=":302"/><ref name=":156"/> Both being the most dominant [[carnivora]]ns of North America in the Late Pleistocene and Holocene respectively, both brown bears and ''Arctodus simus'' exhibit a high degree of dietary variability. Noting that [[Dietary biology of the brown bear|brown bears are largely herbivorous]], meat can be an important dietary element to certain populations. ''Arctodus'' follows a similar eco-morphology- while much evidence suggests herbivory, isotope data from some populations of ''Arctodus'' (such as those in [[Beringia]]) suggests the regular consumption of meat.<ref name=":312" /> Additionally, the potential of [[kleptoparasitism]] is often noted in ''Arctodus'', with brown bears being opportunistic, curious, and regularly steal kills from smaller predators.<ref name=":272"/><ref name=":312" /> Secondly, the spectacled bear (''Tremarctos ornatus''), the closest living relative of ''Arctodus'', is a herbivorous short-faced bear- both bears have been noted to share various adaptations for herbivory.<ref name="Figueiridio_et_al_20102" /> Another extant model for the eco-morphology of ''Arctodus'' may be the [[striped hyena]] and the [[brown hyena]]. ''Arctodus simus'' resembled these two living [[Hyena|hyaenids]], along with the predatory [[spotted hyena]], in skull shape and relative lengths of the trunk, back and limbs. The [[Striped hyena|striped]] and [[brown hyena]]s supplement their diet of large animal carrion and small animal prey with plant material in the form of [[fruit]], which can make up to half of the diet of some individuals of the [[brown hyena]] at certain times of the year.<ref name=":110" /> Another comparison can be made with the omnivorous [[maned wolf]] of [[South America]]. The [[maned wolf]] inhabits [[Grassland|open grassland]], has extremely long and slender limbs relative to body size (as has sometimes been interpreted in ''Arctodus simus''), is not especially fast, nor does it take swift prey, and runs with a loping gait. The long limbs may be an adaptation for increased vision over tall ground cover in an open habitat. However, it is equally possible that the longer limbs of ''Arctodus simus'' were used in tearing and pulling down vegetation, including [[shrub]]s and small trees, in order to feed on [[Leaf|leaves]], [[fruit]]s, [[Bark (botany)|bark]], [[seed]]s and [[flower]]s.<ref name=":132" /><ref name=":162"/> === Herbivory === [[File:Juniperus_communis_fruits_-_Keila.jpg|thumb|231x231px|Bear faeces found at [[The Mammoth Site]] in South Dakota containing [[Juniper berry|''Juniperus'' seeds]] likely belonged to ''Arctodus''. [[Conifer cone|Seed cones]] and [[Berry (botany)|berries]] are still an important food source for northern bears today.]] The fact that ''Arctodus'' did not significantly differ in dentition or build from modern bears has led most authors to support the hypothesis that the ''A. simus'' and the [[cave bear]] were omnivores, like most modern bears, and the former would have eaten plants depending on availability.<ref name="ScienceDaily2">ScienceDaily, 13&nbsp;April 2009.{{cite web |title=Prehistoric bears ate everything and anything, just like modern cousins |url=https://www.sciencedaily.com/releases/2009/04/090408170815.htm |access-date=2009-04-13 |website=ScienceDaily}}</ref> A 2006 study by Sorkin found dental and cranial adaptations for herbivory present in ''Arctodus simus'', suggest that the diet of the ''Arctodus'' included a large amount of plant material. Their cranial adaptations for increased bite force (including the short [[Rostrum (anatomy)|rostrum]]), broad [[Snout|muzzles]] (which would have precluded selective browsing), and the absence of digging adaptations in their forelimbs and claws (which would have limited [[Dietary biology of the brown bear#Plants and fungi|rooting]]) suggest that the plant material in their diet was coarse foliage, which was unselectively grazed.<ref name=":110" /> A 2008 study founds that the mandibular morphology of ''Arctodus simus'' noted that the similarity of ''Arctodus simus'' with the herbivorous ''Tremarctos ornatus'' is likely due to both a mandible shape which housed more primitive characteristics relative to other bears, and a convergence in dietary adaptations towards herbivory.<ref name=":82">{{Cite journal |last=Meloro |first=Carlo |date=2011-03-17 |title=Feeding habits of Plio-Pleistocene large carnivores as revealed by the mandibular geometry |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2011.550357 |journal=Journal of Vertebrate Paleontology |language=en |volume=31 |issue=2 |pages=428–446 |doi=10.1080/02724634.2011.550357 |s2cid=85255472 |issn=0272-4634}}</ref> Paleontologists Steven Emslie and Nicholas Czaplewski suggested that the body size of ''Arctodus simus'' exceeded the expected upper limitations for a [[Quaternary]] terrestrial carnivore (based on the more restrictive energy base for a carnivorous diet). This size discrepancy, along with a [[dentition]] akin to ''[[Spectacled bear|Tremarctos ornatus]]'', indicated a primarily herbivorous diet, but with the potential for opportunistic carnivory.<ref name=":132" /> This was challenged by a 1988 study, specifically on the basis of ''Arctodus''<nowiki/>' skull and body proportions being an impediment to foraging (especially in open areas), and the abundance of contemporary large prey. In particular, despite cranial adaptions strongly aligning with herbivory, a browsing diet foraged from the canopies of trees and shrubs could have been difficult with the large and flattened rostrum and incisor arcade of ''Arctodus''.<ref name=":162"/> However, again, due to the [[gracility]] and lack of agility of ''Arctodus'', ''Arctodus'' could probably neither prey upon adult [[Megafauna|mega-herbivores]],<ref name=":212" /><ref name=":222" /> nor actively chase down nimbler prey.<ref name="Simus2" /><ref name=":212" /> Additionally, studies of mandibular morphology and tooth microwear of bears confirms that short faced bears such as the spectacled bear and ''Arctodus'' were adapted to and actively consumed vegetation, whereas ''Ursus'' is omnivorous.<ref name=":302" /><ref name="Donohue2"/><ref name=":172" /><ref name=":82" /> Morphologically, ''Arctodus simus'' exhibits characteristics common to herbivorous bears. This includes cheek teeth with large surface areas, a deep mandible, and large mandibular muscle attachments (which are rare in carnivorous mammals). Because herbivorous carnivorans lack an efficient digestive tract for breaking down plant matter via microbial action, they must break down plant matter via extensive chewing or grinding, and thus possess features to create a high [[mechanical advantage]] of the jaw.<ref name=":132" /><ref name="Donohue2"/> While features of ''Arctodus simus'' morphology suggest herbivory, their close phylogenetic relationship to the omni-herbivorous [[spectacled bear]] presents the possibility that these traits may be an ancestral condition of the group. Regardless, gross tooth wear suggests consumption of at least some plant matter in the diet of ''Arctodus simus'' at [[La Brea Tar Pits|La Brea]]''.'' Despite presumed variety in the diet of ''Arctodus simus'', the diet of individuals from [[La Brea Tar Pits|La Brea]] were likely less generalized than modern [[American black bear|black bear]], based on the consistency of ''Arctodus''<nowiki/>' tooth wear.<ref name="Donohue2"/> Fossils of bear [[coprolite]]s found in association with ''Arctodus'' remains at [[The Mammoth Site]] in [[South Dakota]] are believed to contain [[Juniper|''Juniperus'']] seeds.<ref name=":292" /> === Opportunistic carnivory === [[File:American_mastodon_with_calf.jpg|thumb|''Arctodus'' may have found young [[proboscidea]]ns to be suitable prey.|left]] Although evidence suggests that ''Arctodus'' also consumed meat, studies suggest that isotope data cannot differentiate between hypercarnivores and omnivores which consume significant amounts of animal matter.<ref name=":110" /> The bite marks found on many bones of ground sloths (''[[Nothrotheriops|Northrotheriops texanus]]'') and young [[proboscidea]]ns at [[Cockroach Bay Aquatic Preserve|Leisey Shell Pit]] in [[Florida]] matched the size of the canine teeth of ''Arctodus pristinus''. It is not known if these bite marks are the result of active predation or scavenging.<ref name=":262"/> Evidence from the [[Δ13C|carbon isotope]] values of an ''Arctodus simus'' individual from [[Cedral, San Luis Potosí|Cedral]], [[San Luis Potosí]], [[Mexico|México]], suggested that ''Arctodus simus'' from this locality preferred areas of closed vegetation. Owing to having only one sample of ''Arctodus simus'' from [[Cedral, San Luis Potosí|Cedral]] and the lack of nitrogen isotopic values, the study found it difficult to infer whether ''Arctodus simus'' was an [[omnivore]] or [[hypercarnivore]]. The [[Δ13C|''δ''<sup>13</sup>C]] value, however, showed that this individual fed upon [[C3 carbon fixation|C3]] resources- in fact, that ''Arctodus'' individual had the strongest [[Δ13C|''δ''<sup>13</sup>C]] value of the fauna studied. ''Arctodus''<nowiki/>' [[Carbon-13|carbon isotope]] value did not overlap with, but was closest to values from the [[tapir]] and ''[[Hemiauchenia]]''. Those animals could have been included in their diet, along with other contemporaneous [[C3 carbon fixation|C3]] herbivores such as [[Camelops|camels]], [[Platygonus|peccaries]], [[Nothrotheriops|Shasta ground sloth]] and [[mastodon]], along with C3 vegetation.<ref name=":410"/> [[File:Smilodon_gaping.jpg|thumb|The enormous canines of sabertooth cats such as ''[[Smilodon]]'' would have made carcass consumption difficult, presenting a scavenging opportunity for ''Arctodus''.]] A likely faunal interaction was between ''[[Smilodon]]'' and ''Arctodus''- the sabretooth cat's theorized inability to consume all but the soft tissue of their kills would leave large portions of the carcass available to scavengers such as ''Arctodus''. ''Arctodus''<nowiki/>' scavenging had the potential to be [[Kleptoparasitism|kleptoparasitic]]- however, in addition to many contemporaneous predators being [[Sociality|gregarious]] and thus better able to defend their kills, ''Arctodus''<nowiki/>' great size variation would have likely limited the frequency of this behavior to all but the largest ''Arctodus simus''.<ref name="Figueiridio_et_al_20102" /> For specimens from inland [[California]] ([[Madera County, California|Fairmead Landfill]]) from the [[Irvingtonian|Middle Pleistocene]], a 2012 study proposed that ''Arctodus simus'' consumed Colombian mammoth, and large [[ungulate]]s- that ''Arctodus'' likely consumed substantial amounts of vegetation made conclusive determinations unclear.<ref name=":72">{{Cite journal |last=Trayler |first=Robin Brendan |date=December 2012 |title=Stable Isotope Records of Inland California Megafauna- New Insights Into Pleistocene Paleoecology and Paleoenvironmental Conditions (Masters Thesis) |url=https://scholarworks.calstate.edu/downloads/h128nf901 |journal=College of Science and Mathematics, California State University Fresno}}</ref> However, the author republished in 2015 with colleagues, recalibrating ''Arctodus''<nowiki/>' [[Δ13C|''δ''<sup>13</sup>C]] values to be closest to [[C3 carbon fixation|C3 vegetation]] consuming ''[[Cervus]]'' and ''[[Mastodon|Mammut]]'', if the consumption of C3 vegetation by ''Arctodus'' is not included.<ref name=":232"/> In the later Californian [[McKittrick Tar Pits]], ''Arctodus simus'' had a diet which included [[deer]] and [[tapir]], similar to the one inferred for the [[Cedral, San Luis Potosí|Cedral]] individual.<ref name=":410" /> [[Alaska]]n specimens were thought to also largely predate upon similar megafauna as proposed for the Fairmead individuals in the 2012 study,<ref name=":272"/> but isotope data suggests [[reindeer]], [[muskox]] and possibly fellow predators and their kills, were regularly consumed.<ref name=":312" /> A single find from the [[Channel Islands (California)|Channel Islands]] of [[California]] replete with nitrogen isotope signatures aligning with [[bison]] and [[Camelidae|camels]] (followed by [[pinniped|seal]]s) bolsters the suggestion that although not entirely carnivorous, ''A. simus'' would have had a flexible diet across its range. That the ''Arctodus'' fossil in the [[Channel Islands (California)|Channel Islands]] was likely transported post-mortem from the [[California|North American mainland]] further complicates the idea of a standard diet for ''Arctodus,'' as the mainland would have had plenty of vegetation to consume. However, the partial reliance on marine resources has been suggested to be as a result of a competitive megafaunal carnivore guild- the marine signal was in between [[island fox]]es and [[bald eagle]]s, most closely resembling Late Pleistocene [[California condor]]s.<ref name=":47"/> Bone damage on a [[Cranium|cranial fragment]] (and possibly the humerus) of an ''Arctodus'' individual in a cave on [[Vancouver Island]] has been attributed to another ''Arctodus'', on the basis that ''Arctodus'' was the only confirmed large terrestrial [[carnivora]]n at the locality.<ref name=":156"/> ''Arctodus'' has been found in association with [[proboscidea]]n remains near [[Frankstown Township, Blair County, Pennsylvania|Frankstown]], [[Pennsylvania]] (juvenile [[mastodon]]), and at [[The Mammoth Site]], [[South Dakota]] ([[Columbian mammoth]]s). However, questions remain as to whether these finds determine a predatory or scavenging relationship, or whether they were simply preserved at the same deposit.<ref name=":292" /><ref>{{Cite web |date=2010-02-17 |title=A Baby Mastodon Deathtrap (?) |url=https://www.nationalgeographic.com/science/article/a-baby-mastodon-deathtrap |access-date=2022-06-09 |website=Science |language=en}}</ref> On the other hand, a [[woolly mammoth]] specimen from [[Saltville, Virginia|Saltville]], [[Virginia]] was likely scavenged on by ''Arctodus simus'', as evidenced by a [[Canine tooth|canine]] gouge through the [[calcaneus]].<ref name=":332" /> Several Columbian mammoth bones from a cave near [[Sanpete County, Utah|Huntington Reservoir]], [[Utah]] also record ursid gnaw marks attributed to ''Arctodus'', with an ''Arctodus'' specimen preserved in association with the remains.<ref name=":382"/> A [[mastodon]] [[humerus]] from the [[Snowmastodon site]] in [[Colorado]] bears tooth marks also suggested to be from ''Arctodus''.{{Citation needed|date=June 2022}} Importantly, the canines of ''[[American lion|Panthera atrox]]'' overlap in size with ''Arctodus simus'', complicating the identification of tooth marks.<ref name=":332" /> However, this is not to discredit all tooth marks attributed to ''Arctodus'', as damaged bones from an ''Arctodus'' den site in Alaska suggest that ''Arctodus'' transported megafaunal [[Long bone|longbones]] back to a cave-like den and chewed on them,<ref>{{Cite journal |last=Sattler |first=Robert A. |date=1997 |title=Large Mammals in Lower Rampart Cave 1, Alaska: Interspecific Utilization of an Eastern Beringian Cave |journal=Geoarchaeology|volume=12 |issue=6 |pages=657–688|doi=10.1002/(SICI)1520-6548(199709)12:6<657::AID-GEA7>3.0.CO;2-Y }}</ref> at a time when lions had a limited overlap with ''Arctodus'' in Beringia.<ref name=":19" /><ref name=":142" /> Furthermore, a perforated [[Platygonus compressus|peccary]] ilium from [[Sheriden Cave]] has also been hypothesised as being scavenged by ''Arctodus simus''.<ref name=":322"/> [[File:SpectacledBear1_CincinnatiZoo.jpg|thumb|222x222px|''Arctodus''<nowiki/>' closest extant relative, the [[spectacled bear]], could provide a behavioural analogue for their extinct [[Tremarctinae|tremarctine]] relatives.]] Endemic to the [[Andes|South American highlands]], the last surviving [[Tremarctinae|short-faced bear]] is the [[spectacled bear]]. Although mostly herbivorous, the modern [[spectacled bear]] is on occasion an active predator. The [[spectacled bear]] has several hunting techniques- principally, the bear surprises or overpowers its prey, mounts its back, and consumes the immobilized animal while still alive, pinning the prey with its weight, large paws and long claws. Alternatively, the bear pursues the prey into rough terrain, hillsides, or precipices, provoking its fall and/or death. After death, the prey is dragged to a safe place (e.g. a forested area) and consumed, leaving only skeletal remains.<ref>{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Grinspan |first2=Gustavo A. |last3=Bocherens |first3=Hervé |last4=Acosta |first4=Walter G. |last5=Jones |first5=Washington |last6=Blanco |first6=Ernesto R. |last7=Prevosti |first7=Francisco |date=November 2014 |title=South American giant short-faced bear (Arctotherium angustidens) diet: evidence from pathology, morphology, stable isotopes, and biomechanics |url=http://naturalis.fcnym.unlp.edu.ar/repositorio/_documentos/sipcyt/bfa004877.pdf |journal=Journal of Paleontology |volume=88 |issue=6 |pages=1240–1250 |doi=10.1666/13-143 |s2cid=54869873}}</ref> These behaviors may be applicable to the giant short-faced bears ''[[Arctotherium]]'' and ''Arctodus''. ==== Beringia ==== Analysis of bones from [[Alaska]] showed high concentrations of [[Isotopes of nitrogen#Nitrogen-15|nitrogen-15]], a stable nitrogen isotope accumulated by carnivores. Additionally, although few specimens exist, there is currently no evidence of the same carbohydrate-related [[Tooth decay|dental pathologies]] evident in southern populations of ''Arctodus simus''.<ref name=":142" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more [[Carnivore|carnivorous]] in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C3 vegetation]], particularly [[Reindeer|caribou]]).<ref name=":312" /><ref name=":412"/> A 2015 study suggests that caribou could not account for the high levels of [[Δ13C|carbon-13]] and [[Nitrogen 15|nitrogen-15]] in some ''Arctodus'' individuals in Beringia. The study suggests that the consumption of [[Muskox|tundra muskox]], which sometimes express high proportions of these isotopes, and possibly other predators in its Beringian range, may explain the data.<ref name=":312" /> Increased carnivory may be due to a lower proportion of competitors and probably a lower availability of carbohydrate-rich food supplies across the year in the far northern latitudes.<ref name=":142" /> Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, a {{Convert|700|kg|lb|abbr=on}} [[Beringia]]n ''Arctodus'' would need to consume ~{{Convert|5853|kg|lb}} of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain {{Convert|100|kg|lb|abbr=on}} of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref> Studies point out that ''A. simus'' would have had a varied diet across its range,<ref name="Donohue2"/> and that the features of the skull and teeth match modern omnivorous bears. Additionally, the isotope data purportedly establishing the carnivory of Beringian ''Arctodus'' overlapped with modern, [[Dietary biology of the brown bear|omni-herbivorous]] brown bears from [[Europe]], eastern [[Wyoming]], and central [[Montana]], demonstrating that isotope data cannot distinguish between [[hypercarnivore]]s and [[omnivore]]s which eat a significant amount of animal matter.<ref name=":110" /> However, this has been challenged on the basis that herbivory should be more obvious in the data gathered from ''Arctodus''.<ref name=":332" /> Regardless, the local extinction of ''Arctodus'' in [[Beringia]] ~23,000 BP,<ref name=":19" /><ref name=":156"/> much earlier than in other parts of its range, raises questions about how suited ''Arctodus'' was to a hypothetically [[Hypercarnivore|carnivorous]] niche, and why, whilst recolonized by [[Panthera spelaea|cave lions]] and [[brown bear]]s, ''Arctodus'' didn't repopulate [[Beringia]] once the ice-free corridor to the south re-opened later in the [[Pleistocene]].<ref name=":19" /><ref name=":182">{{Cite journal |last1=Pedersen |first1=Mikkel W. |last2=Ruter |first2=Anthony |last3=Schweger |first3=Charles |last4=Friebe |first4=Harvey |last5=Staff |first5=Richard A. |last6=Kjeldsen |first6=Kristian K. |last7=Mendoza |first7=Marie L. Z. |last8=Beaudoin |first8=Alwynne B. |last9=Zutter |first9=Cynthia |last10=Larsen |first10=Nicolaj K. |last11=Potter |first11=Ben A. |date=2016 |title=Postglacial viability and colonization in North America's ice-free corridor |url=http://eprints.gla.ac.uk/138297/1/138297.pdf |journal=Nature |volume=537 |issue=7618 |pages=45–49 |bibcode=2016Natur.537...45P |doi=10.1038/nature19085 |pmid=27509852 |s2cid=4450936}}</ref> == Human interaction == [[File:Clovis Point.jpg|thumb|The [[Clovis culture|Clovis people]] are the first known culture to have interacted with ''Arctodus''.|left]]One documented interaction with [[Clovis culture|Clovis people]] is present at the [[Lubbock Lake Landmark]], [[Texas]]. A likely already deceased ''Arctodus simus'' was processed for subsistence (butchery marks indicated skinning, de-fleshing and disarticulation) and technology (raw material resource for tool production), much in the same way as a [[Columbian mammoth|mammoth carcass]] (~13,000 BP / 11,100 [[Carbon-14|<sup>14</sup>C]] BP ).<ref name=":112"/> Additionally, other remains of the ''Arctodus simus'' have been found in association with [[Paleo-Indians|Paleo-Indian]] artifacts in [[Sheriden Cave]], [[Wyandot County, Ohio|Ohio]],<ref name=":282"/><ref name=":322"/><ref name="Redmond2">{{cite web |author=Brian G. Redmond |date=March 2006 |title=Before the Western Reserve: An Archaeological History of Northeast Ohio |url=https://www.cmnh.org/CMNH/media/CMNH_Media/C-R%20Docs/BeforeWR.pdf |access-date=January 28, 2020 |publisher=The Cleveland Museum of Natural History |page=2}}</ref> and Huntington Dam, Utah.<ref name=":382"/> It is clear that people were at least occasionally involved in the death and/or butchery of several different large non-carnivorous Pleistocene mammals, particularly [[mammoth]]s and [[mastodon]]s. This may at times have put people in competition with ''Arctodus simus'' for carcasses, and possibly for prey. Defense against these large bears as well as abandonment of carcasses are plausible outcomes. The relationship between people and ''Arctodus simus'' is likely to have been uneasy at best.<ref name=":156"/> === Migration barrier hypothesis === [[Valerius Geist|Val Geist]] once hypothesized that humans moving into [[North America]] may have found large Pleistocene carnivores such as ''Arctodus simus'' to be a barrier to gaining a foothold.<ref name=":272"/> [[Beringia]]n forms of ''Arctodus'' were the largest and most powerful carnivorous land mammals in North America, with the potential specialization in obtaining and dominating distant and scarce resources. Humans in this hypothesis, though familiar with [[brown bear]]s, would not have been able to effectively contend with the ''Arctodus simus'' and other large Pleistocene carnivores, a situation that would have suppressed human population expansion. However, this has been discredited by modern research- evidence continues to maintain a prolonged co-existence of humans and ''Arctodus'' across North America. ==== Beringia ==== [[File:Ccsm4_beringia_lgm_tundratypes_by_temperature_1.png|thumb|313x313px|[[Beringia]] during the [[Last Glacial Maximum]].]] Humans migrated to North America via the Siberian [[mammoth steppe]], arriving at [[Beringia|Eastern Beringia]] (Alaska and the Yukon). However, the migration was halted at the [[Wisconsin glaciation|North American Ice Sheet]], which separated Beringia and southern North America for most of the Late Pleistocene.<ref>{{Cite journal |last1=Graf |first1=Kelly E. |last2=Buvit |first2=Ian |date=2017-12-01 |title=Human Dispersal from Siberia to Beringia: Assessing a Beringian Standstill in Light of the Archaeological Evidence |url=https://www.journals.uchicago.edu/doi/full/10.1086/693388 |journal=Current Anthropology |volume=58 |issue=S17 |pages=S583–S603 |doi=10.1086/693388 |issn=0011-3204 |s2cid=149080106}}</ref> Both humans and ''Arctodus'' are first dated to ~50,000 BP in Beringia, both from sites in the Yukon, and co-existed until ''Arctodus'' went extinct in Beringia ~23,000 BP during the [[Last Glacial Maximum]]. This co-existence was despite the regional extinction of other Beringian predators such as [[Panthera spelaea|lions]], brown bears and [[Homotherium|saber-tooth cats]]. Important sites of pre-LGM human occupation in Beringia include the [[Old Crow Flats]], [[Kuparuk River|Kuparuk River Valley]] & the [[Bluefish Caves]].<ref>{{Cite journal |last1=Holen |first1=Steven R. |last2=Harington |first2=C. Richard |last3=Holen |first3=Kathleen A. |date=2017 |title=New Radiocarbon Ages on Percussion-Fractured and Flaked Proboscidean Limb Bones from Yukon, Canada |url=https://www.jstor.org/stable/26379757 |journal=Arctic |volume=70 |issue=2 |pages=141–150 |doi=10.14430/arctic4645 |jstor=26379757 |issn=0004-0843}}</ref><ref>{{Cite journal |last1=Bourgeon |first1=Lauriane |last2=Burke |first2=Ariane |last3=Higham |first3=Thomas |date=2017-01-06 |title=Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada |journal=PLOS ONE |language=en |volume=12 |issue=1 |pages=e0169486 |doi=10.1371/journal.pone.0169486 |issn=1932-6203 |pmc=5218561 |pmid=28060931|bibcode=2017PLoSO..1269486B |doi-access=free }}</ref><ref>{{Cite journal |last=Bourgeon |first=Lauriane |date=2021-06-01 |title=Revisiting the mammoth bone modifications from Bluefish Caves (YT, Canada) |url=https://www.sciencedirect.com/science/article/pii/S2352409X21001814 |journal=Journal of Archaeological Science: Reports |language=en |volume=37 |pages=102969 |doi=10.1016/j.jasrep.2021.102969 |s2cid=234816694 |issn=2352-409X}}</ref><ref>{{Cite journal |last1=Goebel |first1=Ted |last2=Hoffecker |first2=John F. |last3=Graf |first3=Kelly E. |last4=Vachula |first4=Richard S. |date=June 2022 |title=Archaeological reconnaissance at Lake E5 in the Brooks Range, Alaska and implications for the early human biomarker record of Beringia |url=https://linkinghub.elsevier.com/retrieve/pii/S0277379122001846 |journal=Quaternary Science Reviews |language=en |volume=286 |pages=107553 |doi=10.1016/j.quascirev.2022.107553|bibcode=2022QSRv..28607553G |s2cid=248736952 }}</ref> ==== Contiguous North America ==== Additionally, the human colonization of North America south of the ice sheets further disproves the idea that ''Arctodus'' was a migration barrier. Pre-[[Last Glacial Maximum|LGM]] sites across the Americas such [[Chiquihuite cave|Chiquihuite Cave]], [[Hueyatlaco|Valsequillo]],<ref>{{Cite journal |last=Pichardo |first=M. |date=1997 |title=Valsequillo biostratigraphy: New evidence for Pre-Clovis date |url=https://www.jstor.org/stable/29540729 |journal=Anthropologischer Anzeiger |volume=55 |issue=3/4 |pages=233–246 |doi=10.1127/anthranz/55/1997/233 |jstor=29540729 |issn=0003-5548}}</ref> El Cedral,<ref>{{Cite journal |last1=Gonzalez |first1=Sofia |last2=Huddart |first2=David |date=2008 |title=The Late Pleistocene Human Occupation of Mexico |url=https://www.researchgate.net/publication/265490787 |journal=FUMDHAMentos VII |via=ResearchGate}}</ref> [[Calico Early Man Site|Calico]], [[Pendejo Cave]] and [[White Sands National Park|White Sands]] suggest that humans co-existed with ''Arctodus'' for many thousands, if not tens of thousands of years. This extensive overlap with ''Arctodus'' across [[North America]] puts significant doubt to the migration barrier hypothesis. The earliest universally accepted post LGM/pre-[[Clovis culture|Clovis]] site is [[Monte Verde]] in Chile, dated to ~15,000 BP. Similarly dated sites from [[Saltville (archaeological site)|Saltville]], La Sena, [[Meadowcroft Rockshelter|Meadowcroft]], [[Topper Site|Topper]], [[Triquet Island]], [[Cactus Hill]], and [[Buttermilk Creek (Texas)|Buttermilk Creek]] in the USA further solidify a rapid human expansion across the Americas.<ref name=":156"/> There is no evidence that ''Arctodus'', or other Pleistocene carnivores below the [[Laurentide Ice Sheet]] were in any way an impediment to the peopling of the Americas. == Extinction == [[File:Arctodus simus skeletal.jpg|thumb|Skeletal reconstruction of ''Arctodus simus''.]]''Arctodus simus'' went extinct around 12,000 years ago, which was relatively late when compared to other victims of the [[Quaternary extinction|Quaternary extinction event]].<ref>{{Cite journal |last1=Faith |first1=J. Tyler |last2=Surovell |first2=Todd A. |date=2009-12-08 |title=Synchronous extinction of North America's Pleistocene mammals |journal=Proceedings of the National Academy of Sciences |volume=106 |issue=49 |pages=20641–20645 |doi=10.1073/pnas.0908153106 |issn=0027-8424 |pmc=2791611 |pmid=19934040 |bibcode=2009PNAS..10620641F |doi-access=free}}</ref> ''Arctodus'' was also one of the last (16 out of 35) North American megafauna to go extinct, having reached the Pleistocene-Holocene boundary (13,800 BP - 11,400 BP).<ref name=":442"/> Various factors, including the depletion in number of large herbivores,<ref name=":34" /> the diminishing nutritional quality of plants during climate change, and competition with fellow omnivores ([[Paleo-Indians|humans]] and [[brown bear]]s) for food resources, have been suggested as the cause of ''Arctodus simus''<nowiki/>' extinction.<ref name=":112"/> However, multiple studies put doubt on brown bears being culpable in ''Arctodus simus''<nowiki/>' extinction.<ref name=":92"/><ref name=":156"/><ref name=":162"/> Moreover, there is no strong evidence that humans hunted large extinct Pleistocene carnivores in North America, and no clear indication of direct human involvement in the extinction of ''Arctodus simus''.<ref name=":156"/> Additionally, no evidence from [[La Brea Tar Pits|Rancho La Brea]] suggests that food shortages were to blame for the demise of ''Arctodus simus'', or other large bodied [[carnivora]]ns.<ref name="Donohue2"/> Of these factors, vegetation shifts in the latest Pleistocene may have been particularly unfavorable for ''Arctodus simus,'' due to a reduction of quality foraging for subsistence. For example, on [[Vancouver Island]] (∼13,500 BP), vegetation changed rapidly from open [[woodland]]s with abundant [[Pinus contorta|lodgepole pine]] to increasingly closed forests with shade-tolerant [[Picea|spruce]], [[Tsuga mertensiana|mountain hemlock]], and [[Alnus rubra|red alder]]. These changes, effective by ∼12,450 BP, point toward cool and moist conditions during the [[Younger Dryas|Younger Dryas stadial]]. Closed forests continued to expand in the [[Greenlandian|early Holocene]], with [[Tsuga heterophylla|western hemlock]] becoming dominant. Even though ''Arctodus simus'' was not restricted to open areas and could occur in different environments, the timing of the regional shift from an open pine [[woodland]] habitat to a densely forested vegetation implies that these vegetation changes contributed to the local extirpation of ''Arctodus simus'', along with many other megafauna.<ref name=":156"/> Loss and turnover of the diversity of mitochondrial DNA before the Last Glacial Maximum has been noted amongst Eurasian and American megafauna such as bison, lions, horses and mammoths. This is predicated by a decrease in population size from a previously genetically diverse population in the Late Pleistocene, followed by either a repopulation from a source population, or extinction at the start of the Holocene. Correspondingly, ''Arctodus simus'' had a very low level of genetic diversity from most sampled specimens, albeit a sample with a Beringian and temporal bias (<44,000 BP). A reduced ability to adapt to environmental conditions has been attributed to a lack of genetic diversity, and this combination has contributed to the endangerment of modern specialized carnivores such as lions and Tasmanian devils. That the individual from Sheriden Cave, Ohio was very closely related to Beringian specimens further may support this idea, as these populations had possibly been isolated from before the Last Glacial Maximum (tens of thousands of years).<ref name=":49" /> A similar level of genetic affinity between Beringian fauna and some southern populations has been found in contemporary camels and horses.<ref>{{Cite journal |last1=Mitchell |first1=Kieren J. |last2=Bover |first2=Pere |last3=Salis |first3=Alexander T. |last4=Mudge |first4=Caitlin |last5=Heiniger |first5=Holly |last6=Thompson |first6=Mary |last7=Hockett |first7=Bryan |last8=Weyrich |first8=Laura S. |last9=Cooper |first9=Alan |last10=Meachen |first10=Julie A. |date=November 2021 |title=Evidence for Pleistocene gene flow through the ice-free corridor from extinct horses and camels from Natural Trap Cave, Wyoming |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618221005589 |journal=Quaternary International |language=en |pages=S1040618221005589 |doi=10.1016/j.quaint.2021.11.017|s2cid=244706923 }}</ref> Small population sizes may also be characteristic of tremarctine bears- the spectacled bear, while having low levels of genetic diversity, has no signs of a recent genetic bottleneck. However, brown bears, along with many recently immigrated taxa, had diverse, [[Sympatry|sympatric]] source populations in Eurasia, allowing for repopulations/reinvasions into the Americas. If ''Arctodus simus'' experienced genetic bottlenecks or local extinctions prior to the Last Glacial Maximum, ''Arctodus'' would have been unable to supplement their reduced genetic diversity with new migrants like the brown bear could, making them vulnerable to extinction.<ref name=":49" /> The youngest date for ''Arctodus simus'' is circa 12,700 BP from [[San Antonio|Friesenhahn Cave]], [[Texas]], calibrated from 10,814 ± 55 [[radiocarbon year]]s ([[Carbon-14|<sup>14</sup>C]] BP). However, this date should be viewed with caution, as analyses suggest the collagen protein was degraded. A vertebra from [[Bonner Springs, Kansas|Bonner Springs]], [[Kansas]], was dated to ca. 12,800 BP (based on 10,921 ± 50 radiocarbon years) from well preserved collagen. However, another radiocarbon date from a different laboratory on the same vertebra widens the possible age of the vertebra to between 9,510 and 11,021 <sup>14</sup>C BP (at 2''σ''). Nevertheless, a specimen from [[Huntington North Dam|Huntington Dam]], [[Utah]] was also dated to ca. 12,800 BP from two radiocarbon dates (10,870 ± 75 & 10,976 ± 40 <sup>14</sup>C BP) and is therefore considered reliable.<ref name=":122" /><ref name=":442" /> == Directly sampled specimens == === Radiocarbon dated specimens === Below is a table collating [[Radiocarbon dating|radiocarbon dates]] directly sampled from ''Arctodus simus'' specimens (not including dates from associated remains nor stratigraphy).<ref name="Pedersen 2728–2736.e8" /><ref name=":24" /><ref name=":49" /><ref name=":12" /><ref name=":272"/><ref name=":156"/><ref name="sciencedirect.com" /><ref name=":47">{{Cite journal |last1=Mychajliw |first1=Alexis M. |last2=Rick |first2=Torben C. |last3=Dagtas |first3=Nihan D. |last4=Erlandson |first4=Jon M. |last5=Culleton |first5=Brendan J. |last6=Kennett |first6=Douglas J. |last7=Buckley |first7=Michael |last8=Hofman |first8=Courtney A. |date=2020-09-16 |title=Biogeographic problem-solving reveals the Late Pleistocene translocation of a short-faced bear to the California Channel Islands |journal=Scientific Reports |volume=10 |issue=1 |pages=15172 |doi=10.1038/s41598-020-71572-z |pmc=7494929 |pmid=32938967}}</ref><ref name=":44">{{Cite journal |last=Stuart |first=Anthony John |date=May 2015 |title=Late Quaternary megafaunal extinctions on the continents: a short review: LATE QUATERNARY MEGAFAUNAL EXTINCTIONS |url=https://onlinelibrary.wiley.com/doi/10.1002/gj.2633 |journal=Geological Journal |language=en |volume=50 |issue=3 |pages=338–363 |doi=10.1002/gj.2633 |s2cid=128868400}}</ref><ref name=":45">{{Cite journal |last1=Fox-Dobbs |first1=Kena |last2=Dundas |first2=Robert. G. |last3=Trayler |first3=Robin B. |last4=Holroyd |first4=Patricia A. |date=January 2014 |title=Paleoecological implications of new megafaunal 14 C ages from the McKittrick tar seeps, California |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2013.791694 |journal=Journal of Vertebrate Paleontology |language=en |volume=34 |issue=1 |pages=220–223 |doi=10.1080/02724634.2013.791694 |issn=0272-4634 |s2cid=128943450}}</ref><ref>{{Cite journal |last1=O'Keefe |first1=F. Robin |last2=Fet |first2=Elizabeth V. |last3=Harris |first3=John M. |date=2009-12-04 |title=Compilation, calibration, and synthesis of faunal and floral radiocarbon dates, Rancho La Brea, California |url=https://www.biodiversitylibrary.org/part/226783 |journal=Contributions in Science |volume=518 |pages=1––16 |doi=10.5962/p.226783 |s2cid=128107590 |issn=0459-8113}}</ref><ref>{{Cite journal |last1=Mann |first1=Daniel H. |last2=Groves |first2=Pamela |last3=Reanier |first3=Richard E. |last4=Gaglioti |first4=Benjamin V. |last5=Kunz |first5=Michael L. |last6=Shapiro |first6=Beth |date=2015-11-17 |title=Life and extinction of megafauna in the ice-age Arctic |journal=Proceedings of the National Academy of Sciences |language=en |volume=112 |issue=46 |pages=14301–14306 |doi=10.1073/pnas.1516573112 |issn=0027-8424 |pmc=4655518 |pmid=26578776|bibcode=2015PNAS..11214301M |doi-access=free }}</ref><ref>{{Cite journal |last=Storer |first=J. |date=2003 |editor-last=Froese |editor-first=D.G. |editor2-last=Zazula |editor2-first=G. D. |title=Vertebrate Palaeontology of the Klondike Area |url=https://emrlibrary.gov.yk.ca/Tourism/international-mammoth-conference-third-field-guide-2003.pdf |journal=3rd International Mammoth Conference Field Guide to Quaternary Research in the Klondike Goldfields |volume=Occasional Papers in Earth Sciences No. 6 |pages=24–29 |via=Palaeontology Program, Government of the Yukon}}</ref><ref name=":11" /> {| class="wikitable sortable" |+ !Location !Element & ID !<sup>14</sup>C Date (1''σ'') !<sup>14</sup>C Range (2''σ)'' !Calibrated dates |- |[[San Antonio|Friesenhahn Cave]], [[Texas]] |[[Wisdom tooth|M3]] [[Molar (tooth)|molar]] [[dentin]]e (TMM 933–2205) |10,814 ± 55 BP |10,704–10,924 BP |12,700 BP |- |[[Bonner Springs, Kansas|Bonner Springs]] ([[Kansas River|Kansas River/ Kaw River Bank]]), [[Kansas]] |[[Lumbar vertebrae|Lumbar vertebra]] (KUVP 81230) ~ [[Femur]] (KUVP 131586) |9630 ± 60 BP 10,921 ± 50 BP¹ 11,688 ± 50 BP |N/A 10,821–11,021 BP¹ 11,588–11,788 BP |12,800 BP¹ |- |[[Sanpete County, Utah|Huntington Dam]], [[Utah]] |[[Maxilla]] (UMNH VP 9510) |10,870 ± 75 BP 10,976 ± 40 BP |~ 10,896–11,056 BP |12,800 BP |- |[[McKittrick Tar Pits|McKittrick Tar Seeps]], [[California]] |[[Ulna]] (UCMP 153245) |11,040 ± 310 BP |N/A |N/A |- |[[Fulton County, Indiana|Fulton County]], [[Indiana]] |[[Rib]] |11,500 ± 520 BP* |N/A |N/A |- |[[Sheriden Cave]], [[Ohio]] |[[Carpal bones|Scapholunar]] (CMNH 2001) ~ ~ [[Talus bone|Astragalus]] ~ |11,480 ± 60 BP 11,566 ± 40 BP¹ 11,570 ± 50 BP 11,570 ± 70 BP 11,610 ± 90 BP |11,486–11,646 BP¹ |N/A |- |[[Nimpkish Lake|Pellucidar Cave]], [[Vancouver Island]] |[[Palatine bone|Palatine]] (PC2–1c) M2 molar dentine (PC2–1a) [[Humerus]] (PC2-3) |11,615 ± 30 BP 11,720 ± 50 BP 11,775 ± 30 BP |N/A |13,379–13,557 BP 13,477–13,725 BP 13,575–13,964 BP |- |[[Salt Lake Valley]] ([[Lake Bonneville|Bonneville]]), [[Utah]] |Femur (UVP 015/1) |12,650 ± 70 BP* |N/A |N/A |- |[[San Miguel Island]] (Daisy Cave), California |[[Metacarpal bones|Metacarpal I]] (PSU-5973) |14,130 ± 70 BP |N/A |17,009 ± 135 BP |- |[[Saltville (archaeological site)|Saltville Valley]], [[Virginia]] |M2 molar dentine |14,853 ± 55 BP |N/A |N/A |- |[[Camden County, Missouri|Perkins Cave]], [[Missouri]] |Dentine |16,910 ± 50 BP |N/A |N/A |- |[[Frontier County, Nebraska|La Sena]], [[Nebraska]] |I3 [[incisor]] dentine |19,487 ± 95 BP |19,297–19,677 BP |N/A |- |[[Natural Trap Cave]], [[Wyoming]] |KU 31956 |20,220 ± 150 BP |N/A |24,300 ± 208 BP |- |Cleary ([[Fairbanks, Alaska|Fairbanks]]), [[Alaska]] |F:AM 30492 |20,524 ± 180 BP? |N/A |N/A |- |[[Bonanza Creek|Eldorado Creek (Loc.45)]], [[Yukon]] |[[Calcaneus|Calcaneum]] (CMN37957/FM177762) |22,417 ± 452 BP |N/A |N/A |- |[[Last Chance Creek|Hester Creek]], Hunker Creek, Yukon |NMC-50367 |24,850 ± 150 BP |N/A |N/A |- |[[Ester, Alaska|Ester]] (Fairbanks), Alaska |F:AM 30494 |25,496 ± 224 BP |N/A |N/A |- |[[Dawson City|Gold Run Creek]], Yukon |Cranium (NMC-7438 (<s>NMC 7468</s>)) |26,040 ± 270 BP |N/A |N/A |- |Indet. [[Last Chance Creek|Hunker Creek]], Yukon Hester Creek, Hunker Creek, Yukon |Radius (YG 76.4) Ulna (CMN-49874) |26,520 ± 110 BP¹ 26,720 ± 290 BP |N/A |30,800 BP¹ |- |[[Indian River (Yukon)|Quartz Creek]], Yukon |N/A, YT03/134 |26,940 ± 570 BP |N/A |N/A |- |[[Alaska North Slope|Ikpikpuk River]], Alaska |Humerus (ROM:VP 43646) |27,160 ± 280 BP |N/A |N/A |- |[[Chatanika, Alaska|Upper Cleary Creek]] ([[Fairbanks North Star Borough, Alaska|Fairbanks North Star]]), Alaska |A-37-I0 |27,511 ± 279 |N/A |N/A |- |[[Dawson City|Canyon Creek]], Yukon |Femur (fragment, YG 546.562) |27,850 ± 220 BP |N/A |31,800 BP |- |[[La Brea Tar Pits]], California |Humerus (LACMRLP 19258) [[Metatarsal bones|Metatarsal]] (LACMRLP 54077) [[Cervical vertebrae|Cervical VI]] (LACMRLP 42063) |27,330 ± 140 BP 28,130 ± 330 BP 28,350 ± 470 BP |N/A |N/A |- |[[Dawson City|Lower Hunker Creek (80 pup)]], Yukon |Humerus (NMC 37577) |29,695 ± 1200 BP |N/A |N/A |- |[[Adair County, Oklahoma|Gittin Down Mountain Cave]], [[Oklahoma]] |M2 molar dentine (UAM75-839-1) |34,063 ± 460 BP |33,143–34,983 BP |N/A |- |[[Alleghany County, Virginia|Island Ford Cave]], Virginia |M1 molar dentine (USNM 521336) |34,080 ± 480 BP |33,120–35,040 BP |N/A |- |[[Birch Creek (Yukon River tributary)|Birch Creek]], Alaska |"Birch" |34,974 ± 652 BP |N/A |N/A |- |Ester (Fairbanks), Alaska |AMNH 99209 |39,565 ± 1126 BP |N/A |N/A |- |[[Sixtymile River]] (Loc. 3), Yukon |NMC-42388 |44,240 ± 930 BP |N/A |N/A |- |[[Alaska North Slope|Titaluk River]], Alaska |[[Metapodial]] (UAMES T99-033) |42,600 ± 2,200 BP 46,500 ± 3,600 BP |N/A |43,570 BP 49,016 BP |- |[[Dawson City|Ophir Creek]], Yukon |[[Petrous bone|Petruous bone]] (YG 24.1 / CRH- 95–3) |46,500 BP¹ <s>(20,210 ± 110 BP)</s> |N/A |49,800 BP¹ |} === DNA samples === This table collates the current DNA samples extracted from ''Arctodus'' specimens, with their associated [[haplogroup]]s.<ref name="Pedersen 2728–2736.e8" /><ref name=":28" /><ref name=":49">{{Cite thesis |last=Bray |first=Sarah C. E. |date=September 2010 |title=Mitochondrial DNA Analysis of the Evolution and Genetic Diversity of Ancient and Extinct Bears |url=https://digital.library.adelaide.edu.au/dspace/bitstream/2440/66285/8/02whole.pdf |publisher=School of Environmental and Earth Sciences, University of Adelaide |pages=214 (230)}}</ref><ref name=":11">{{Cite journal |last1=Salis |first1=Alexander T. |last2=Gower |first2=Graham |last3=Schubert |first3=Blaine W. |last4=Soibelzon |first4=Leopoldo H. |last5=Heiniger |first5=Holly |last6=Prieto |first6=Alfredo |last7=Prevosti |first7=Francisco J. |last8=Meachen |first8=Julie |last9=Cooper |first9=Alan |last10=Mitchell |first10=Kieren J. |date=2021-03-10 |title=Ancient genomes reveal hybridisation between extinct short-faced bears and the extant spectacled bear (Tremarctos ornatus) |url=https://www.biorxiv.org/content/10.1101/2021.02.05.429853v2 |language=en |pages=2021.02.05.429853 |doi=10.1101/2021.02.05.429853|s2cid=231885176 }}</ref> {| class="wikitable sortable" |+ !Location !DNA extract ID !<sup>14</sup>C Date (1''σ'') & source !Calibrated dates & Haplogroups |- |[[Chiquihuite cave|Chiquihuite Cave]], [[Zacatecas]] |UE1605 |11,419 ± 34 BP / 11,942 ± 33 / 12,901 ± 75 BP (sediments) |13,000 - 15,000 BP |- |Sheriden Cave, Ohio |ACAD 1734A |11,619 ± 40 BP phalange, CMNHS VP8289) |Haplogroup E |- |Eldorado Creek (Loc.45), Yukon |ACAD 424A/NC011116 |22,417 ± 452 BP (calcaneum, CMN37957/FM177762)) |Haplogroup A |- |"Alaska" |ACAD 450A |25,264 ± 650 BP (humerus, AMNH "ALASKA Bx35‟) |Haplogroup A |- |Hester Creek, Yukon |ACAD 344 & PH092 |26,520 ± 110 BP (radius, YG 76.4) |30,800 BP, Haplogroup A |- |Hester Creek (Loc.57), Yukon |ACAD 330A & AC688 |26,720 ± 270 BP (ulna, CMN49874) |Haplogroup A |- |[[Indian River (Yukon)|Quartz Creek]], Yukon |ACAD1954A |26,940 ± 570 BP (N/A, YT03/134) |Haplogroup D |- |Canyon Creek, Yukon |N/A |27,850 ± 220 BP (femur, YG 546.562) |31,800 BP |- |Sixtymile, Yukon |ACAD 438A & IB187 |44,240 ± 930 BP (metacarpal, CMN 42388) |Haplogroup F |- |Ophir Creek, Yukon |PH095 |46,500 BP (petruous bone, YG 24.1) |49,800 BP, Haplogroup F |- |[[Edmonton]] (Pit #48), [[Alberta]] |ACAD 346A |Radius, P96.2.38 |Haplogroup F |- |Gold Run, Yukon |ACAD 428A |Femur, CMN34556 |Haplogroup A |- |[[Goldstream, Alaska|Goldstream]], Alaska |ACAD 436A |Ulna (pathology), AMNH A-1828 |Haplogroup B |- |Goldstream, Alaska |ACAD 437A |Radius, #850 575 UCLA |Haplogroup C |- |Ester Creek, Alaska |ACAD 441A |Humerus, FAM 95656 |Haplogroup A |- |No.2 G-Strip Area ("Goldstream"), Alaska |ACAD 443A |Ramus, AMNH A-82- 1039 |Haplogroup G |- |Natural Trap Cave, Wyoming |ACAD 5177 |KU 31956 |N/A |- |[[Ester, Alaska|Eva Creek Mine]], Alaska |BS3 |Femur, PM-97-001-100 |Haplogroup D |- |Hunker Creek (80 Pup), Alaska |BS71 |N/A, CMN 44566 |Haplogroup A |- |"[[Dawson City|Dawson area]]", Yukon |BS72 |Tibia, CMN 36236 |Haplogroup D |- |Hunker Creek, Yukon |BS73 |N/A, CMN 42335 |Haplotype A |- |[[Livengood, Alaska|Lillian Creek]], Alaska |BS74 |Humerus, UAF/Paleo V-55-524 |Haplogroup A |- |[[North Pole, Alaska|Dawson Cut]], Alaska |IB191 |Fibula, AMNH A-676- 5625 |Haplogroup F |- |[[Fort Selkirk|Cripple Creek]], Yukon |IB195 |Tibia, AMNH A-217- 2297 |Haplogroup F |- |Dawson, Yukon |IB255 |N/A, CMN 37577 |Haplogroup A |- |Hester Creek, Yukon |JW131 |Ulna, YT03/288 Cat. No. 129.1 (JS) |Haplogroup A |} ==== Haplotype cladogram ==== Below is a cladogram exploring the relationships between the [[Mitochondrial DNA|mitochondrial]] haplogroups of ''Arctodus simus''. Other than the specimen from [[Chiquihuite cave]], all specimens form a single clade.<ref name="Pedersen 2728–2736.e8" /><ref name=":49" />{{clade sequential |1={{clade |1=''[[Tremarctos]]'' [[File:Spectacled bear (1829).jpg|75px]] |2=''[[Arctotherium]]'' }} |2=Chiquihuite Cave |3={{clade |1=A |2=B |3=C }} |4={{clade |1=D |2=E }} |5={{clade |1=F |2=G }} }} ==See also== *''[[Arctotherium]]'' *''[[Agriotherium]]'' *[[Pleistocene megafauna]] *[[Quaternary extinction|Quaternary Extinction Event]] ==References== {{commons category|Arctodus}} {{Reflist}} {{Ursidae extinct nav}} {{Taxonbar|from=Q2626037}} [[Category:Pleistocene bears]] [[Category:Pleistocene carnivorans]] [[Category:Pleistocene extinctions]] [[Category:Prehistoric mammals of North America]] [[Category:Pleistocene mammals of North America]] [[Category:Extinct animals of the United States]] [[Category:Extinct animals of Mexico]] [[Category:Fossil taxa described in 1854]] [[Category:Apex predators]]'
Unified diff of changes made by edit (edit_diff)
'@@ -70,14 +70,14 @@ ==Description== === Size === -[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and 317&nbsp;kg, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" /> +[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and {{Convert|317|kg|lb|abbr=on}}, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" /> Though over 100 giant short-faced bear localities in [[North America]] are known, only one site produced a [[baculum]] (penis bone) that could belong to ''Arctodus simus''. The lack of recovered ''Arctodus'' [[Baculum|bacula]] likely reflects both [[taphonomy]] and behaviour. The majority of skeletal remains representing large individuals are from open sites where usually only a few elements were recovered. In contrast, horizontal (walk-in) cave passages produced numerous examples of small, yet relatively complete individuals where [[Baculum|bacula]] would likely be found if they had been present. Both the small size of recovered skeletal elements and the lack of [[Baculum|bacula]] from cave deposits suggest that female individuals of ''A. simus'' were using caves, in line with [[Bear|ursid]] maternal denning.<ref name=":2">{{Cite journal|last1=CHUBERT|first1=BLAINE|last2=KAUFMANN|first2=JAMES|date=2003-08-01|title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species|url=https://www.researchgate.net/publication/252748398|journal=Journal of Cave and Karst Studies|volume=65}}</ref><ref name=":3">{{Cite journal|last1=Fowler|first1=Nicholas L.|last2=Spady|first2=Thomas J.|last3=Wang|first3=Guiming|last4=Leopold|first4=Bruce D.|last5=Belant|first5=Jerrold L.|date=October 2021|title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51|issue=4|pages=465–481|doi=10.1111/mam.12246|s2cid=233847639 }}</ref> Therefore, in conjunction with ursid sexual dimorphism (e.g. in [[spectacled bear]]s, males are 30%-40% larger than females), the largest individuals are often considered male, particularly older males, with the smaller individuals being females.<ref name=":02"/><ref name=":12">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |doi=10.1016/j.quaint.2009.11.010 |bibcode=2010QuInt.217..188S }}</ref><ref name=":46">{{Cite journal |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |journal=PaleoBios |volume=15 |issue=2 |pages=27–36 |date=May 24, 1993 |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf}}</ref> -Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~555&nbsp;kg.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1994 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~372&nbsp;kg, smaller than recovered [[brown bear]] remains (~455&nbsp;kg, although these remains may postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~770&nbsp;kg from six specimens.<ref name=":7" /> +Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~{{Convert|555|kg|lb}}.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1998 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~{{Convert|372|kg|lb}}, smaller than recovered [[brown bear]] remains (~{{Convert|455|kg|lb}}, although these remains postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~{{Convert|770|kg|lb}} from six specimens.<ref name=":7" /> -Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between 1,200&nbsp;kg and 412&nbsp;kg,<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between 957&nbsp;kg (~1,000&nbsp;kg) and 317&nbsp;kg.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref> +Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between {{Convert|1200|kg|lb}} and {{Convert|412|kg|lb}},<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between {{Convert|957|kg|lb}} and {{Convert|317|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref> === Data === -Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]].<ref name=":6" /><ref name=":62"/> Also included are the mean figures from [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref> +Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]],<ref name=":6" /><ref name=":62"/> and some associated weight estimates.<ref name="Figueiridio_et_al_20102" /> Also included is the mean from 9 specimens in [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref> {| class="wikitable sortable" |+ @@ -88,5 +88,5 @@ !Ratio of TL to TW (M) x 100 !Standard Deviation -!Number +!Estimated weight (kg) |- |P.89.13.91, [[Edmonton]] @@ -96,5 +96,5 @@ |9.0 |~ -|1 +|~ |- |UVP 015/1, Utah @@ -104,5 +104,5 @@ |8.9 |~ -|1 +|957 |- |UC 3721, [[Shasta Lake|Potter Creek Cave]] @@ -112,5 +112,5 @@ |8.3 |~ -|1 +|~ |- |F:AM 25531, [[Hay Springs, Nebraska|Hay Springs]] @@ -120,5 +120,5 @@ |9.5 |~ -|1 +|863 |- |UM 25611, [[Meade, Kansas|Jinglebob]] @@ -128,5 +128,5 @@ |8.5 |~ -|1 +|388 |- |UC 44687, [[Irvington, California|Irvington]] @@ -136,5 +136,5 @@ |9.1 |~ -|1 +|~ |- |LACMNH-Z75, [[La Brea Tar Pits|Rancho La Brea]] @@ -144,5 +144,5 @@ |~ |~ -|1 +|317 |- |U.S.A. sites, x̄ values (Kurtén, 1967) @@ -152,5 +152,5 @@ |8.1-9.5 (x̄= 8.7) |0.45 -|9 +|~ |} @@ -158,5 +158,5 @@ ==== Skull ==== [[File:Arctodus simus skull Cleveland.jpg|thumb|''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], [[Ohio]]]] -Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] are likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" /> +Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] were likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" /> The skull also has a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance; this broad [[snout]] possibly housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas (although this is characteristic shared with the omni-herbivorous spectacled bear).<ref name=":7" /><ref name=":132">{{Cite journal |last1=Emslie |first1=Steven D. |last2=Czaplewski |first2=Nicholas J. |date=1985-11-15 |title=A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology |url=https://www.biodiversitylibrary.org/partpdf/226835 |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793}}</ref><ref name=":402">{{Cite journal |last=Matheus |first=Paul E. |date=1995-11-01 |title=Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0033589485710903 |journal=Quaternary Research |language=en |volume=44 |issue=3 |pages=447–453 |doi=10.1006/qres.1995.1090 |bibcode=1995QuRes..44..447M |s2cid=83542760 |issn=0033-5894}}</ref><ref>{{Cite journal |last1=Goswami |first1=Anjali |last2=Milne |first2=Nick |last3=Wroe |first3=Stephen |date=2011-06-22 |title=Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1713 |pages=1831–1839 |doi=10.1098/rspb.2010.2031 |issn=0962-8452 |pmc=3097826 |pmid=21106595}}</ref> The [[Orbit (anatomy)|orbits]] of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat [[Lateral (anatomy)|laterally orientated]] (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the [[brown bear]], suggesting that [[Stereopsis|stereoscopic vision]] was not a priority.<ref name=":110"/><ref name=":302"/><ref name=":292">{{Cite book |last=Baryshnikov |first=Gennady |url=https://www.researchgate.net/publication/336916777 |title=The Hot Springs Mammoth Site: A Decade of Field and Laboratory Research in Paleontology, Geology and Paleoecology |publisher=The Mammoth Site of Hot Springs, South Dakota Inc. |year=1994 |editor-last=Agenbroad |editor-first=Larry D. |pages=Chapter 16 |editor-last2=Mead |editor-first2=Jim I.}}</ref> @@ -172,5 +172,5 @@ Although the shape of the [[Elbow|elbow joint]] suggests ''Arctodus'', ''[[Arctotherium|Arctotherium bonariense]]'', and ''[[Arctotherium|Arctotherium wingei]]'' had the possibility of retaining [[Arboreal locomotion|semi-arboreal]] adaptations, the size of the elbow joint condemns ''Arctodus'' to terrestrial life. As the [[Medial epicondyle of the humerus|medial epicondyle]] is particularly expanded in these species, it is likely that ''Arctodus'' and ''Arctotherium'' (just like the [[giant panda]]) retained this characteristic to attain a higher degree of forelimb dexterity. Whether this dexterity facilitated [[Scavenger|scavenging]] or [[Herbivore|herbivory]], this high degree of proximal dexterity was probably advantageous for these species, and retained in tremarctine bears despite their general tendency towards terrestriality.<ref name=":28">{{Cite journal|last1=Mitchell|first1=Kieren J.|last2=Bray|first2=Sarah C.|last3=Bover|first3=Pere|last4=Soibelzon|first4=Leopoldo|last5=Schubert|first5=Blaine W.|last6=Prevosti|first6=Francisco|last7=Prieto|first7=Alfredo|last8=Martin|first8=Fabiana|last9=Austin|first9=Jeremy J.|last10=Cooper|first10=Alan|date=2016-04-30|title=Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America|journal=Biology Letters|volume=12|issue=4|pages=20160062|doi=10.1098/rsbl.2016.0062|pmc=4881349|pmid=27095265}}</ref><ref name=":132"/><ref name="Meloro 133–146">{{Cite journal|last1=Meloro|first1=Carlo|last2=de Oliveira|first2=Alessandro Marques|date=2019-03-01|title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |journal=Journal of Mammalian Evolution |volume=26|issue=1|pages=133–146|doi=10.1007/s10914-017-9413-x|s2cid=25839635 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf}}</ref> -A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" /> +A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" /> ''Arctodus'' likely had a top speed of {{Convert|40-45|km/h|mph}}, and based on hyaenid proportions, would shift from singlefoot locomotion to a pace at {{Convert|8.5|km/h|mph|abbr=on}}, and would begin to gallop at {{Convert|18.5|km/h|mph|abbr=on}}, a fairly high speed. Based on other mammals, the optimal pace speed of ''Arctodus'' would have been {{Convert|13.7|km/h|mph|abbr=on}}, which would have also been rather fast for moderate speed travel. For comparison, hyenas cross country ~{{Convert|10|km/h|mph|abbr=on}}.<ref name=":212" /> The [[paw]]s ([[metapodial]]s and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''' paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the first digit ([[Toe|hallux]]) of ''Arctodus'' was positioned more closely and parallel to the other four digits (i.e. with straight toes, ''Arctodus'' had less lateral splaying).<ref name=":272">{{Cite thesis |title=Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia |url=https://scholarworks.alaska.edu/handle/11122/9491 |date=1997 |degree=PhD |language=en |first=Paul Edward |last=Matheus}}</ref> This theory is potentially contradicted by trackways tentatively attributed to ''Arctodus'' from near [[Lakeview, Oregon|Lakeview]] in [[Oregon]]. The trackways, which fit the dimensions of ''Arctodus simus''<nowiki/>' paws, exhibit extreme toe splaying, with three centrally aligned, evenly spaced toes at the front, and two almost perpendicular toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had an oval-shaped, undivided pad on its sole (with no toe pad impressions), with front paws that were slightly larger than its back paws, possessed long claws, and had its hind foot overstep the forefoot when walking, like modern bears.<ref>{{Cite web |last1=Packard |first1=E.L. |last2=Allison |first2=I.S. |last3=Cressman |first3=L.S. |title=Mammalian Tracks in the Late Pliocene or Early Pleistocene Beds of Lake County Oregon |url=https://www.oregongeology.org/milo/archive/MiningDistricts/LakeCounty/UnclassifiedDistrict/LakeCountyFossilLocalities/LakeCountyFossilLocalitiesReports.pdf |access-date=June 11, 2017 |website=Oregon Geology}}</ref> For comparison, the [[Manus (anatomy)|manus]] of the spectacled bear has five digits arrayed in a shallow arc, and claws which are quite long, and which also extend far in front of their respective digits.<ref>{{Cite journal |last=Weems |first=Robert E. |date=2018 |title=An Early Pleistocene (Early Irvingtonian) Footprint Fauna from the Bacons Castle Formation, Westmoreland Formation, Virginia |url=https://www.researchgate.net/publication/348579743 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=79 |pages=731–748 |via=ResearchGate}}</ref> Some claw marks attributed to ''Arctodus simus'' at [[Riverbluff Cave]] (as they were four meters above the floor of the cave) were nearly 20&nbsp;cm in width.<ref name=":1">{{Cite journal |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |title=Cenozoic Vertebrate Tracks and Traces |last2=Spielmann |first2=Justin A. |last3=Lockley |first3=Martin G. |date=2007 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=42 |language=en}}</ref> @@ -421,7 +421,7 @@ One past proposal, suggested by [[Björn Kurtén]], envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed the [[megafauna]] of the Pleistocene with its great physical strength.<ref name=":162"/> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":212">{{Cite book |last=E. |first=Matheus, Paul |title=Locomotor adaptations and ecomorphology of short-faced bears (Arctodus simus) in eastern Beringia |date=2003 |publisher=Yukon Palaeontologist, Gov't. of Yukon |oclc=243520303}}</ref><ref name=":222">{{Cite book |last=Randally |first=Lynch, Eric |title=Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics |date=2012-08-06 |publisher=East Tennessee State University |oclc=818344518}}</ref> significantly more [[Gracility|gracile]] so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":202">{{Cite journal |last1=SOIBELZON |first1=LEOPOLDO H. |last2=SCHUBERT |first2=BLAINE W. |date=2011 |title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears |journal=Journal of Paleontology |volume=85 |issue=1 |pages=69–75 |doi=10.1666/10-037.1 |jstor=23019499 |s2cid=129585554}}</ref> -Because its long legs may have enabled ''Arctodus'' to run at speeds of {{Convert|50|-|70|km/h|abbr=on|sigfig=1|mph}}, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref name=":212" /><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/> +Due to their long legs, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. Correspondingly, although a 700''&nbsp;''kg ''Arctodus'' may have been able to reach a maximum speed of {{Convert|51|km/h|mph}}, all modern bears have maximum speeds significantly lower than mass based calculations for speed- such speeds would have likely exceeded skeletal strength with their bulk. As a result, paleontologist Paul Matheus suggests that ''Arctodus''<nowiki/>' top speed was {{Convert|40-45|km/h|mph|abbr=on}}. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/> -Additionally, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/> +Moreover, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/> However, analysis of the forelimb of ''Arctodus'' suggests the bear could have been in the early stages of [[cursorial]] evolution- ''A. simus'' was somewhat more prone to [[Cursorial|cursorial tendencies]], being capable of more efficient locomotion, ''A. simus'' was interpreted as capable of high-speed (relative to extant bears), straight-line locomotion, and was likely more adept at pursuing large prey than the extant [[Polar bear|polar]] and [[brown bear]]s.<ref name=":222" /> However, that the limbs are elongated in the proximal rather than distal limb segments, had a plantigrade gait, and a stride which had little to no unsupported intervals, put doubt to this theory.<ref name=":132"/> Moreover, the pronation of the forearm and the flexion of the wrist and digits, and more lightly muscled forelimbs, all of which are crucial to grasping a large prey animal with the forepaws, were probably less powerful in ''Arctodus'' than in either the [[brown bear]] or in ''[[Panthera]].''<ref name=":110" /> @@ -432,5 +432,5 @@ [[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|[[American mastodon]] arm bone with ''A.&nbsp;simus'' tooth marks at the [[Denver Museum of Nature & Science]] in [[Denver]], [[Colorado]]]] [[File:Shortfacedbear-1070375.jpg|thumb|226x226px|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of [[Molar (tooth)|molar]] damage associated with processing bone, [[Tooth decay|dental cavities]], and the lack of specialisation in the [[Canine tooth|canines]], discourages a [[Hypercarnivore|hyper-carnivorous]] interpretation of ''Arctodus''.]] -''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by paleontologist Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref> +''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref> This idea was challenged by a comprehensive review by paleontologist Borja Figueirido and colleagues in 2010,<ref name="Figueiridio_et_al_20102" /> a 2013 study of the micro-wear of the teeth of various extant and extinct bears (examining ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]]), and a 2015 study focusing on [[carnivora]]ns recovered from [[Rancho La Brea]].<ref name="Donohue2">{{cite journal |author1=Donohue, Shelly L. |author2=DeSantis, Larisa R. G. |author3=Schubert, Blaine W. |author4=Ungar, Peter S. |year=2013 |title=Was the giant short-faced bear a hyper-scavenger? A new approach to the dietary study of ursids using dental microwear textures |journal=PLOS ONE |volume=8 |issue=10 |page=e77531 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name=":172">{{Cite journal |last1=DeSantis |first1=Larisa |last2=Schubert |first2=Blaine |last3=Schmitt-Linville |first3=Elizabeth |last4=Ungar |first4=Peter |last5=Donohue |first5=Shelly |last6=Haupt |first6=Ryan |date=2015-01-01 |title=Dental Microwear Textures of Carnivorans from the La Brea Tar Pits, California, and Potential Extinction Implications |url=https://www.researchgate.net/publication/282253545 |journal=La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas |pages=37–52}}</ref> Specialized scavengers like [[hyena]]s show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from [[La Brea Tar Pits|Rancho La Brea]], researchers concluded that ''Arctodus simus'' was not a specialized scavenger. Of living bears, this population of ''A. simus'' showed the most similar tooth wear patterns to its closest living relative, the [[spectacled bear]], which can have a highly varied diet- from obligate omnivory to, on the most part, being almost purely herbivorous in diet.<ref name=":132" /> However, this depends on the region, and seasonal availability.<ref name="Donohue2"/> Additionally, the higher rates of tooth breakage at La Brea were revisited, and due to a relative lack of bone related microwear on other carnivorans (even lower than the modern day) was attributed to the hunting of larger prey, and the acquisition and/or defense of kills.<ref name=":172" /> Moreover, severe tooth crown fractures and alveolar infections were found in the South American giant short faced bear ([[Arctotherium|''Arctotherium'' ''angustidens'']]). These were interpreted as evidence of feeding on tough materials (e.g. bones), which could tentatively indicate for these bears the regular scavenging of ungulate carcasses obtained through [[kleptoparasitism]]. However, such dental pathologies were not observed in the specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_20102" /> Additionally, the short, broad [[Rostrum (anatomy)|rostrum]] of ''Arctodus'' is a characteristic also shared with the [[sun bear]] and the [[spectacled bear]], which are both [[Omnivore|omnivorous]].<ref name="Figueiridio_et_al_20102" /> Moreover, isotope analyses of Beringian ''Arctodus'' specimens suggest that ''Arctodus'' had a low consumption rate of horses and mammoths in Beringia, despite those species making up ~50% of the available biomass in Beringia.<ref name=":312"/> @@ -477,5 +477,5 @@ Analysis of bones from [[Alaska]] showed high concentrations of [[Isotopes of nitrogen#Nitrogen-15|nitrogen-15]], a stable nitrogen isotope accumulated by carnivores. Additionally, although few specimens exist, there is currently no evidence of the same carbohydrate-related [[Tooth decay|dental pathologies]] evident in southern populations of ''Arctodus simus''.<ref name=":142" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more [[Carnivore|carnivorous]] in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C3 vegetation]], particularly [[Reindeer|caribou]]).<ref name=":312" /><ref name=":412"/> A 2015 study suggests that caribou could not account for the high levels of [[Δ13C|carbon-13]] and [[Nitrogen 15|nitrogen-15]] in some ''Arctodus'' individuals in Beringia. The study suggests that the consumption of [[Muskox|tundra muskox]], which sometimes express high proportions of these isotopes, and possibly other predators in its Beringian range, may explain the data.<ref name=":312" /> Increased carnivory may be due to a lower proportion of competitors and probably a lower availability of carbohydrate-rich food supplies across the year in the far northern latitudes.<ref name=":142" /> -Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, the average (700&nbsp;kg) [[Beringia]]n ''Arctodus'' individual needed to consume ~5853&nbsp;kg of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain 100&nbsp;kg of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref> +Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, a {{Convert|700|kg|lb|abbr=on}} [[Beringia]]n ''Arctodus'' would need to consume ~{{Convert|5853|kg|lb}} of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain {{Convert|100|kg|lb|abbr=on}} of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref> Studies point out that ''A. simus'' would have had a varied diet across its range,<ref name="Donohue2"/> and that the features of the skull and teeth match modern omnivorous bears. Additionally, the isotope data purportedly establishing the carnivory of Beringian ''Arctodus'' overlapped with modern, [[Dietary biology of the brown bear|omni-herbivorous]] brown bears from [[Europe]], eastern [[Wyoming]], and central [[Montana]], demonstrating that isotope data cannot distinguish between [[hypercarnivore]]s and [[omnivore]]s which eat a significant amount of animal matter.<ref name=":110" /> However, this has been challenged on the basis that herbivory should be more obvious in the data gathered from ''Arctodus''.<ref name=":332" /> '
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[ 0 => '[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and {{Convert|317|kg|lb|abbr=on}}, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" />', 1 => 'Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~{{Convert|555|kg|lb}}.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1998 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~{{Convert|372|kg|lb}}, smaller than recovered [[brown bear]] remains (~{{Convert|455|kg|lb}}, although these remains postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~{{Convert|770|kg|lb}} from six specimens.<ref name=":7" />', 2 => 'Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between {{Convert|1200|kg|lb}} and {{Convert|412|kg|lb}},<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between {{Convert|957|kg|lb}} and {{Convert|317|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref>', 3 => 'Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]],<ref name=":6" /><ref name=":62"/> and some associated weight estimates.<ref name="Figueiridio_et_al_20102" /> Also included is the mean from 9 specimens in [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref>', 4 => '!Estimated weight (kg)', 5 => '|~', 6 => '|957', 7 => '|~', 8 => '|863', 9 => '|388', 10 => '|~', 11 => '|317', 12 => '|~', 13 => 'Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] were likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" />', 14 => 'A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" /> ''Arctodus'' likely had a top speed of {{Convert|40-45|km/h|mph}}, and based on hyaenid proportions, would shift from singlefoot locomotion to a pace at {{Convert|8.5|km/h|mph|abbr=on}}, and would begin to gallop at {{Convert|18.5|km/h|mph|abbr=on}}, a fairly high speed. Based on other mammals, the optimal pace speed of ''Arctodus'' would have been {{Convert|13.7|km/h|mph|abbr=on}}, which would have also been rather fast for moderate speed travel. For comparison, hyenas cross country ~{{Convert|10|km/h|mph|abbr=on}}.<ref name=":212" />', 15 => 'Due to their long legs, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. Correspondingly, although a 700''&nbsp;''kg ''Arctodus'' may have been able to reach a maximum speed of {{Convert|51|km/h|mph}}, all modern bears have maximum speeds significantly lower than mass based calculations for speed- such speeds would have likely exceeded skeletal strength with their bulk. As a result, paleontologist Paul Matheus suggests that ''Arctodus''<nowiki/>' top speed was {{Convert|40-45|km/h|mph|abbr=on}}. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/>', 16 => 'Moreover, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/>', 17 => '''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref>', 18 => 'Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, a {{Convert|700|kg|lb|abbr=on}} [[Beringia]]n ''Arctodus'' would need to consume ~{{Convert|5853|kg|lb}} of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain {{Convert|100|kg|lb|abbr=on}} of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref>' ]
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[ 0 => '[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and 317&nbsp;kg, with an average weight of ~{{Convert|625|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref name=":6">{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_20102"/> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition finds revealing an ''Arctodus simus'' individual well within the size range of ''A. s. yukonensis'' in [[Florida]] (deep within the supposed range of ''A. s. simus''),<ref name=":02"/> and the reverse being found in the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> A high degree of sexual dimorphism, along with morphological diversity likely due to geographic and temporal variation, has also been noted from ''A. pristinus'' specimens from Florida.<ref name=":5" />', 1 => 'Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.5|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<ref name=":162">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160}}</ref> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102"/> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~555&nbsp;kg.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref> Additionally, a 1994 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~372&nbsp;kg, smaller than recovered [[brown bear]] remains (~455&nbsp;kg, although these remains may postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~770&nbsp;kg from six specimens.<ref name=":7" />', 2 => 'Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between 1,200&nbsp;kg and 412&nbsp;kg,<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between 957&nbsp;kg (~1,000&nbsp;kg) and 317&nbsp;kg.<ref name="Figueiridio_et_al_20102"/> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":302">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref>', 3 => 'Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]].<ref name=":6" /><ref name=":62"/> Also included are the mean figures from [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2 |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref>', 4 => '!Number', 5 => '|1', 6 => '|1', 7 => '|1', 8 => '|1', 9 => '|1', 10 => '|1', 11 => '|1', 12 => '|9', 13 => 'Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_20102"/><ref name=":302"/> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436}}</ref><ref name=":13">{{Cite journal |last1=Bureau of Economic Geology |last2=Slaughter |first2=Bos H. |last3=Crook |first3=Wilson W. |last4=Harris |first4=R.K. |last5=Allen |first5=D.C. |last6=Bureau of Economic Geology |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |url=http://begstore.beg.utexas.edu/store/reports-of-investigations/2559-ri0048d.html |doi=10.23867/ri0048d}}</ref> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] are likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" />', 14 => 'A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of this huge bear.<ref name="Figueiridio_et_al_20102"/><ref name=":110"/><ref name=":272" />', 15 => 'Because its long legs may have enabled ''Arctodus'' to run at speeds of {{Convert|50|-|70|km/h|abbr=on|sigfig=1|mph}}, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_20102"/><ref name=":212" /><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name=":212" /><ref name="Simus2"/>', 16 => 'Additionally, the morphology of the lumbar vertebrae of ''Arctodus'' limited acceleration, as it does in the brown bear . The vertebral spines of ''Arctodus'' were tight & rectangular, with no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column. Subsequently, a limited capacity for [[flexion]] and extension in the [[sagittal plane]] likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated eyes, ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":110"/>', 17 => '''Arctodus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. The large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> Notably proposed by paleontologist Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus2" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":110" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":212" /> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":110" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[ruminant]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272"/> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion]]s from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore suggesting species both scavenged more actively, and utilized carcasses more fully.<ref name=":332"/> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":292"/><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21–22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last1=Blinnikov |first1=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |bibcode=2011QSRv...30.2906B |issn=0277-3791}}</ref>', 18 => 'Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, the average (700&nbsp;kg) [[Beringia]]n ''Arctodus'' individual needed to consume ~5853&nbsp;kg of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain 100&nbsp;kg of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272"/><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</ref>' ]
All external links added in the edit (added_links)
[]
All external links in the new text (all_links)
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'https://books.google.com/books?id=3loD7lTLBxgC&dq=Arctodus+haplodon&pg=PA204', 15 => 'https://books.google.com/books?id=mkMZAAAAYAAJ&q=haplodon&pg=PA763', 16 => 'https://www.sciencedirect.com/science/article/pii/S104061820900442X', 17 => 'https://ui.adsabs.harvard.edu/abs/2010QuInt.217...53F', 18 => '//doi.org/10.1016%2Fj.quaint.2009.11.036', 19 => '//www.worldcat.org/issn/1040-6182', 20 => 'https://www.sciencedirect.com/science/article/pii/S1040618209001633', 21 => 'https://ui.adsabs.harvard.edu/abs/2010QuInt.212..187A', 22 => '//doi.org/10.1016%2Fj.quaint.2009.05.012', 23 => '//doi.org/10.3138%2F9781487574154-012', 24 => '//doi.org/10.1016%2Fj.cub.2021.04.027', 25 => '//hdl.handle.net/10037%2F22808', 26 => '//pubmed.ncbi.nlm.nih.gov/33878301', 27 => 'https://api.semanticscholar.org/CorpusID:233303447', 28 => 'http://sedici.unlp.edu.ar/handle/10915/5361', 29 => '//doi.org/10.1127%2F0077-7749%2F2008%2F0250-0001', 30 => 'https://www.researchgate.net/publication/250071137', 31 => 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Whether or not the change was made through a Tor exit node (tor_exit_node)
false
Unix timestamp of change (timestamp)
'1662272051'
Retrieved from "https://en.wikipedia.org/wiki/Special:AbuseLog/33307505"