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{{Short description|Extinct genus of dinosaurs}}
{{speciesbox
{{speciesbox
| fossil_range = [[Early Cretaceous]], {{fossil range|124.5|120}}
| fossil_range = [[Early Cretaceous]], {{fossil range|124.5|120}}
| image = Sapeornis chaoyangensis.JPG
| image = Sapeornis chaoyangensis NMNS.jpg
| image_caption = Fossil specimen, Hong Kong Science Museum
| image_caption = Fossil specimen, [[National Museum of Natural Science]]
| genus = Sapeornis
| genus = Sapeornis
| parent_authority = [[Zhonghe Zhou|Zhou]] & [[Fucheng Zhang|Zhang]], 2002
| parent_authority = [[Zhonghe Zhou|Zhou]] & [[Fucheng Zhang|Zhang]], 2002
Line 9: Line 10:
| display_parents = 3
| display_parents = 3
| synonyms =
| synonyms =
{{collapsible list|bullets = false
⚫
* ''[[Omnivoropteryx sinousaorum]]''? <small>Czerkas & Ji, 2002</small>
* ''Didactylornis jii'' <small>Yuan, 2008</small>
|title=<small>Genus synonymy</small>
* ''Sapeornis angustis'' <small>Zhou & Zhang, 2009</small>
| ''Didactylornis'' <small>Yuan, 2008</small>
| ''Shenshiornis'' <small>Hu, 2010</small>
⚫
* ''Shenshiornis primita'' <small>Hu ''et al.'', 2010</small><ref>{{cite journal | last1 = Hu | first1 = D.| year = 2010 | title = A new sapeornithid bird from China and its implication for early avian evolution | url = | journal = Acta Geologica Sinica | volume = 84 | issue = 3| pages = 472–482 | doi=10.1111/j.1755-6724.2010.00188.x|display-authors=etal}}</ref>
}}
{{collapsible list|bullets = true
|title=<small>Species synonymy</small>
⚫
| ?''[[Omnivoropteryx sinousaorum]]'' <small>Czerkas & Ji, 2002</small>
| ''Sapeornis angustis'' <small>Zhou & Zhang, 2009</small>
| ''Didactylornis jii'' <small>Yuan, 2008</small>
⚫
| ''Shenshiornis primita'' <small>Hu, 2010</small><ref>{{cite journal | last1 = Hu | first1 = D.| year = 2010 | title = A new sapeornithid bird from China and its implication for early avian evolution | journal = Acta Geologica Sinica | volume = 84 | issue = 3| pages = 472–482 | doi=10.1111/j.1755-6724.2010.00188.x| bibcode = 2010AcGlS..84..472H| s2cid = 86441777|display-authors=etal}}</ref>
}}
}}
}}


'''''Sapeornis''''' is a type of [[Avialae|avialan]] which lived during the early [[Cretaceous period]] ([[Aptian|late Aptian]] to early [[Albian]], roughly 125-120 [[mya (unit)|mya]]). The [[genus]] ''Sapeornis'' contains only one species, '''''Sapeornis chaoyangensis'''''.
'''''Sapeornis''''' is a monotypic genus of [[Avialae|avialan]] [[dinosaur]]s which lived during the early [[Cretaceous period]] ([[Barremian|late Barremian]] to early [[Aptian]], roughly 125-120 [[mya (unit)|mya]]). ''Sapeornis'' contains only one species, '''''Sapeornis chaoyangensis'''''.


==Description==
==Description==
Line 21: Line 30:
''Sapeornis'' was large for an early avialan, about {{convert|30|-|33|cm|ft}} long in life, excluding the tail feathers.
''Sapeornis'' was large for an early avialan, about {{convert|30|-|33|cm|ft}} long in life, excluding the tail feathers.


The hand of ''Sapeornis'' was far more advanced than that of ''[[Archaeopteryx]]''. It had three fingers, the outer ones with two and the middle one with three [[phalanges]], and a well-fused [[carpometacarpus]]. Its arms were about half again as long as the legs, suggesting a large wing area. On the other hand, its shoulder girdle was apparently ill-adapted to flapping flight and its [[furcula]] was unusual, with a [[hypocleidum]] similar to more advanced avialans but a general anatomy even more primitive than in ''Archaeopteryx''.<ref name=senter2006>{{cite journal | last1 = Senter | first1 = Phil | year = 2006 | title = Scapular orientation in theropods and basal birds, and the origin of flapping flight | url = http://www.app.pan.pl/acta51/app51-305.pdf | format = PDF | journal = Acta Palaeontologica Polonica | volume = 51 | issue = 2| pages = 305–313 }}</ref> The [[humerus]] was large and bore holes, apparently to save weight, as in the [[Confuciusornithidae]].
The hand of ''Sapeornis'' was far more derived than that of ''[[Archaeopteryx]]''. It had three fingers, the outer ones with two and the middle one with three [[phalanges]], and a well-fused [[carpometacarpus]]. Its arms were about half again as long as the legs, suggesting a large wing area. On the other hand, its shoulder girdle was apparently ill-adapted to flapping flight and its [[furcula]] was unusual, with a [[hypocleidum]] similar to more advanced avialans but a general anatomy even more basal than in ''Archaeopteryx''.<ref name=senter2006>{{cite journal | last1 = Senter | first1 = Phil | year = 2006 | title = Scapular orientation in theropods and basal birds, and the origin of flapping flight | url = https://app.pan.pl/archive/published/app51/app51-305.pdf | journal = Acta Palaeontologica Polonica | volume = 51 | issue = 2| pages = 305–313 }}</ref> The [[humerus]] was large and bore holes, apparently to save weight, as in the [[Confuciusornithidae]].


The skull has a handful of teeth in the upper jawtip only. ''Sapeornis'' had [[gastralium|gastralia]] but no (or unossified) [[uncinate processes of ribs|uncinate processes]]. The breastbone ([[sternum]]) was either absent or, more likely, made of cartilage rather than bone, as in more primitive theropods.<ref name=foth_sternum>Foth, C. (2014). Comment on the absence of ossified sternal elements in basal paravian dinosaurs. ''Proceedings of the National Academy of Sciences'', '''111'''(50): E5334-E5334. {{doi|10.1073/pnas.1419023111}}</ref> The [[pygostyle]] was rod-like as in ''[[Confuciusornis]]'' and ''[[Nomingia]]'', but like in the former there was no long bony tail anymore. While the [[tarsometatarsus|tarsometatarsi]] were more fused than in ''Archaeopteryx'', the [[fibula]] was long and reached the distal point of the tarsal joint, not reduced as in more modern birds (and some non-avian theropods like ''[[Avimimus]]''). The first toe pointed backwards. In specimen [[Institute of Vertebrate Paleontology and Paleoanthropology|IVPP]] V12375, the stomach contained numerous small [[gastrolith]]s. Analysis of its skeletal bones suggest that it had an [[ontogeny]] and slow growth like ''[[Archaeopteryx]]'' and small carnivorous dinosaurs, rather than the explosively fast growth seen in modern birds.<ref>{{cite journal | last1 = Erickson | first1 = Gregory M. | last2 = Rauhut | first2 = Oliver W. M. | last3 = Zhou | first3 = Zhonghe | last4 = Turner | first4 = Alan H | last5 = Hu | first5 = Brian D. | last6 = -1#Inouye | first6 = Dongyu | last7 = Norell | first7 = Mark A. | year = 2009 | title = ''Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in ''Archaeopteryx | doi=10.1371/journal.pone.0007390 | journal = PLOS ONE | volume = 4| issue = | pages = e7390| pmid=19816582 | pmc=2756958}}</ref>
The skull has a handful of teeth in the upper jawtip only. ''Sapeornis'' had [[gastralium|gastralia]] but no (or unossified) [[uncinate processes of ribs|uncinate processes]]. The breastbone ([[sternum]]) was either absent or, more likely, made of cartilage rather than bone, as in more basal theropods.<ref name=foth_sternum>Foth, C. (2014). Comment on the absence of ossified sternal elements in basal paravian dinosaurs. ''Proceedings of the National Academy of Sciences'', '''111'''(50): E5334-E5334. {{doi|10.1073/pnas.1419023111}}</ref> The [[pygostyle]] was rod-like as in ''[[Confuciusornis]]'' and ''[[Nomingia]]'', but like in the former there was no long bony tail anymore. While the [[tarsometatarsus|tarsometatarsi]] were more fused than in ''Archaeopteryx'', the [[fibula]] was long and reached the distal point of the tarsal joint, not reduced as in more modern birds (and some non-avian theropods like ''[[Avimimus]]''). The first toe pointed backwards. In specimen [[Institute of Vertebrate Paleontology and Paleoanthropology|IVPP]] V12375, the stomach contained numerous small [[gastrolith]]s. Analysis of its skeletal bones suggest that it had an [[ontogeny]] and slow growth like ''[[Archaeopteryx]]'' and small carnivorous dinosaurs, rather than the explosively fast growth seen in modern birds.<ref>{{cite journal | last1 = Erickson | first1 = Gregory M. | last2 = Rauhut | first2 = Oliver W. M. | last3 = Zhou | first3 = Zhonghe | last4 = Turner | first4 = Alan H. | last5 = Inouye | first5 = Brian D. | last6 = Hu | first6 = Dongyu | last7 = Norell | first7 = Mark A. | year = 2009 | title = Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in ''Archaeopteryx'' | doi=10.1371/journal.pone.0007390 | journal = PLOS ONE | volume = 4| issue = 10 | pages = e7390| pmid=19816582 | pmc=2756958| bibcode = 2009PLoSO...4.7390E | doi-access = free }}</ref>


In absolute number of features shared with modern birds, ''S. chaoyangensis'' is about as advanced as ''Confuciusornis''. However, the [[apomorph]]ies were largely different from ''Confuciusornis'', and a character analysis demonstrates that these two were not closely related.<ref name=zhou&zhang2006>{{cite journal | last1 = Zhou | first1 = Zhonghe | last2 = Zhang | first2 = Fucheng | year = 2006 | title = A beaked basal ornithurine bird (Aves, Ornithurae) from the Lower Cretaceous of China | url = | journal = [[Zoologica Scripta|Zool. Scripta]] | volume = 35 | issue = | pages = 363–373 | doi = 10.1111/j.1463-6409.2006.00234.x }}</ref> The tail plumage of ''Sapeornis'' consisted of rectrices that formed a graded, fan-like structure. The reduced fingers suggest that it might have had an [[alula]]. Not being well-adapted to flapping flight, ''Sapeornis'' probably was a glider and/or soarer that preferred more open country compared to the Enantiornithes and predominantly woodland birds, although it was able to perch on branches. The small gastroliths, overall large size, and the inferred habitat indicate that ''Sapeornis'' was most likely a [[herbivore]], possibly eating plant seeds and fruits.<ref name=zhou&zhang2003/>
In absolute number of features shared with modern birds, ''S. chaoyangensis'' is about as derived as ''Confuciusornis''. However, the [[apomorph]]ies were largely different from ''Confuciusornis'', and a character analysis demonstrates that these two were not closely related.<ref name=zhou&zhang2006>{{cite journal | last1 = Zhou | first1 = Zhonghe | last2 = Zhang | first2 = Fucheng | year = 2006 | title = A beaked basal ornithurine bird (Aves, Ornithurae) from the Lower Cretaceous of China | journal = [[Zoologica Scripta|Zool. Scripta]] | volume = 35 | issue = 4 | pages = 363–373 | doi = 10.1111/j.1463-6409.2006.00234.x | s2cid = 85222311 }}</ref> The tail plumage of ''Sapeornis'' consisted of rectrices that formed a graded, fan-like structure. The reduced fingers suggest that it might have had an [[alula]]. Not being well-adapted to flapping flight, ''Sapeornis'' probably was a glider and/or soarer that preferred more open country compared to the Enantiornithes and predominantly woodland birds, although it was able to perch on branches. The small gastroliths, overall large size, and the inferred habitat indicate that ''Sapeornis'' was most likely a [[herbivore]], possibly eating plant seeds and fruits.<ref name=zhou&zhang2003/>


Comparisons between the [[sclerotic ring|scleral ring]]s of ''Sapeornis'' and modern birds and reptiles indicate that it may have been [[Diurnality|diurnal]], similar to most modern birds.<ref>{{cite journal|author1=Schmitz, L. |author2=Motani, R. |year=2011 |title=Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology |journal=Science |volume=332 |issue= 6030|pages= 705–8|doi=10.1126/science.1200043 |pmid=21493820}}</ref>
Comparisons between the [[sclerotic ring|scleral ring]]s of ''Sapeornis'' and modern birds and reptiles indicate that it may have been [[Diurnality|diurnal]], similar to most modern birds.<ref>{{cite journal|author1=Schmitz, L. |author2=Motani, R. |year=2011 |title=Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology |journal=Science |volume=332 |issue= 6030|pages= 705–8|doi=10.1126/science.1200043 |pmid=21493820|bibcode=2011Sci...332..705S |s2cid=33253407 }}</ref>


==Discovery and history==
==Discovery and history==
[[File:Sapeornis Holotype IVPP.jpg|left|thumb|229x229px|Holotype (IVPP V12698), [[Paleozoological Museum of China]]]]
''Sapeornis'' is known from fossils found in [[Jiufotang Formation]] and [[Yixian Formation]] rocks in western Liaoning, China. These rocks formed during the [[Aptian|late Aptian]] through early [[Albian]] epochs of the Cretaceous period, and are about 125-120 million years old. Several nearly complete skeletons have been found.<ref name=zhou&zhang2003>Zhou, Zhonghe & Zhang, Fucheng (2003): Anatomy of the primitive bird ''Sapeornis chaoyangensis'' from the Early Cretaceous of Liaoning, China. ''Canadian Journal of Earth Sciences'' '''40'''(5): 731–747. {{doi|10.1139/E03-011}} (HTML abstract)</ref>
''Sapeornis'' is known from fossils found in [[Jiufotang Formation]] and [[Yixian Formation]] rocks in western Liaoning, China. These rocks formed during the [[Aptian|late Aptian]] through early [[Albian]] epochs of the Cretaceous period, and are about 125-120 million years old. Several nearly complete skeletons have been found.<ref name=zhou&zhang2003>Zhou, Zhonghe & Zhang, Fucheng (2003): Anatomy of the primitive bird ''Sapeornis chaoyangensis'' from the Early Cretaceous of Liaoning, China. ''Canadian Journal of Earth Sciences'' '''40'''(5): 731–747. {{doi|10.1139/E03-011}} (HTML abstract)</ref>


The first known specimen (the [[type specimen]]) of ''Sapeornis'' was an incomplete skeleton dug up from Jiufotang Formation rocks in the area of Shangheshou, near [[Chaoyang City]] in Liaoning Province, China in the summer of 2000. It was discovered by a team from the [[Institute of Vertebrate Paleontology and Paleoanthropology]] (IVPP), and was reported in 2002 by the scientists Zhonghe Zhou and Fucheng Zhang. They chose the name in honor of SAPE, the [[Society of Avian Paleontology and Evolution]], which they combined with the [[Ancient Greek]] word ''όρνις'' (ornis), meaning "bird". The species name ''chaoyangensis'' is [[Latin]] for "from Chaoyang".<ref name=sapeornis2>Zhou, Z., & Zhang, F. (2003). Anatomy of the primitive bird ''Sapeornis chaoyangensis'' from the Early Cretaceous of Liaoning, China. ''Canadian Journal of Earth Sciences'', '''40'''(5): 731-747. {{doi|10.1139/E03-011}}</ref> Soon after this, two more, nearly complete specimens were discovered in the Dapingfang area, about {{convert|40|km|mi}} from the original fossil site. None of these first three specimens preserved traces of feathers, but based on the size of their skeletons alone, they were recognized as the largest early Cretaceous avialans known at the time.<ref name=sapeornis2/>
The first known specimen (the [[type specimen]]) of ''Sapeornis'' was an incomplete skeleton dug up from Jiufotang Formation rocks in the area of Shangheshou, near [[Chaoyang City]] in Liaoning Province, China in the summer of 2000. It was discovered by a team from the [[Institute of Vertebrate Paleontology and Paleoanthropology]] (IVPP), and was reported in 2002 by the scientists Zhonghe Zhou and Fucheng Zhang.<ref name="Sapeornis">{{Cite journal |last1=Zhou |first1=Z. |last2=Zhang |first2=F. |year= 2002 |title= Largest Bird from the Early Cretaceous and Its Implications for the Earliest Avian Ecological Diversification |journal= Naturwissenschaften |volume= 89 |issue= 1 |pages= 34–38 |doi= 10.1007/s00114-001-0276-9 |pmid= 12008971 |bibcode=2002NW.....89...34Z |s2cid=1116829 }}</ref> They chose the name in honor of SAPE, the [[Society of Avian Paleontology and Evolution]], which they combined with the [[Ancient Greek]] word ''όρνις'' (ornis), meaning "bird". The species name ''chaoyangensis'' is [[Latin]] for "from Chaoyang".<ref name=sapeornis2>Zhou, Z., & Zhang, F. (2003). Anatomy of the primitive bird ''Sapeornis chaoyangensis'' from the Early Cretaceous of Liaoning, China. ''Canadian Journal of Earth Sciences'', '''40'''(5): 731-747. {{doi|10.1139/E03-011}}</ref> Soon after this, two more, nearly complete specimens were discovered in the Dapingfang area, about {{convert|40|km|mi}} from the original fossil site. None of these first three specimens preserved traces of feathers, but based on the size of their skeletons alone, they were recognized as the largest early Cretaceous avialans known at the time.<ref name=sapeornis2/>


In 2008, Yuan named a new specimen related to ''Sapeornis'' as ''Didactylornis jii''. Yuan concluded that ''Didactylornis'' differed from ''Sapeornis'' in the proportions of the foot and number of wing and foot bones.<ref>{{Cite journal|author=Yuan, C.|year=2008|title=A new genus and species of Sapeornithidae from Lower Cretaceous in western Liaoning, China|journal=Acta Geologica Sinica|volume=82|issue=1|pages=48–55|doi=10.1111/j.1755-6724.2008.tb00323.x}}</ref> However, the relevant portions of the specimen were badly crushed, and later authors concluded that these differences were based on misinterpretation of the poorly preserved specimen. In a 2010 survey of Chinese avialan fossils, Li and colleagues considered ''Didactylornis'' a synonym of ''Sapeornis chaoyangensis''.<ref name=basalbird2010>{{cite journal | last1 = Li | first1 = D. | last2 = Sulliven | first2 = C. | last3 = Zhou | first3 = Z. | last4 = Zhang | first4 = Z. | year = 2010 | title = Basal birds from China: a brief review | url = | journal = Chinese Birds | volume = 1 | issue = 2| pages = 83–96 | doi = 10.5122/cbirds.2010.0002 }}</ref> In a 2012 study, Gao ''et al.'' concluded that ''Didactylornis'' was indeed a junior synonym of ''Sapeornis chaoyangensis'', as were ''Shenshiornis'' and the supposed second species of ''Sapeornis'', ''S. angustis''.<ref name=chiappesapeornis2012>{{cite journal | last1 = Gao | first1 = C. | last2 = Chiappe | first2 = L.M. | last3 = Zhang | first3 = F. | last4 = Pomeroy | first4 = D.L. | last5 = Shen | first5 = C. | last6 = Chinsamy | first6 = A. | last7 = Walsh | first7 = M.O. | year = 2012 | title = A subadult specimen of the Early Cretaceous bird ''Sapeornis chaoyangensis'' and a taxonomic reassessment of sapeornithids | url = | journal = Journal of Vertebrate Paleontology | volume = 32 | issue = 5| pages = 1103–1112 | doi = 10.1080/02724634.2012.693865 }}</ref> ''[[Omnivoropteryx]]'' is also likely synonymous with ''Sapeornis''.<ref name="Holtz2008">Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' [http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2010.pdf Winter 2010 Appendix.]</ref>
In 2008, Yuan named a new specimen related to ''Sapeornis'' as ''Didactylornis jii''. Yuan concluded that ''Didactylornis'' differed from ''Sapeornis'' in the proportions of the foot and number of wing and foot bones.<ref>{{Cite journal|author=Yuan, C.|year=2008|title=A new genus and species of Sapeornithidae from Lower Cretaceous in western Liaoning, China|journal=Acta Geologica Sinica|volume=82|issue=1|pages=48–55|doi=10.1111/j.1755-6724.2008.tb00323.x|bibcode=2008AcGlS..82...48Y |s2cid=86691693 }}</ref> However, the relevant portions of the specimen were badly crushed, and later authors concluded that these differences were based on misinterpretation of the poorly preserved specimen. In a 2010 survey of Chinese avialan fossils, Li and colleagues considered ''Didactylornis'' a synonym of ''Sapeornis chaoyangensis''.<ref name=basalbird2010>{{cite journal | last1 = Li | first1 = D. | last2 = Sullivan | first2 = C. | last3 = Zhou | first3 = Z. | last4 = Zhang | first4 = Z. | year = 2010 | title = Basal birds from China: a brief review | journal = Chinese Birds | volume = 1 | issue = 2| pages = 83–96 | doi = 10.5122/cbirds.2010.0002 | s2cid = 84976296 }}</ref> In a 2012 study, Gao ''et al.'' concluded that ''Didactylornis'' was indeed a junior synonym of ''Sapeornis chaoyangensis'', as were ''Shenshiornis'' and the supposed second species of ''Sapeornis'', ''S. angustis''.<ref name=chiappesapeornis2012>{{cite journal | last1 = Gao | first1 = C. | last2 = Chiappe | first2 = L.M. | last3 = Zhang | first3 = F. | last4 = Pomeroy | first4 = D.L. | last5 = Shen | first5 = C. | last6 = Chinsamy | first6 = A. | last7 = Walsh | first7 = M.O. | year = 2012 | title = A subadult specimen of the Early Cretaceous bird ''Sapeornis chaoyangensis'' and a taxonomic reassessment of sapeornithids | journal = Journal of Vertebrate Paleontology | volume = 32 | issue = 5| pages = 1103–1112 | doi = 10.1080/02724634.2012.693865 | bibcode = 2012JVPal..32.1103G | s2cid = 86195304 }}</ref> ''[[Omnivoropteryx]]'' is also likely synonymous with ''Sapeornis''.<ref name="Holtz2008">Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' [http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2010.pdf Winter 2010 Appendix.]</ref>


==References==
==References==
Line 40: Line 50:


==External links==
==External links==
* [http://www.physorg.com/news/2011-09-early-cretaceous-birds-crops-china.html Early cretaceous birds with crops found in China]
* [http://www.physorg.com/news/2011-09-early-cretaceous-birds-crops-china.html Early Cretaceous birds with crops found in China]


{{Portal|Paleontology}}
{{Portal|Paleontology}}
{{Paraves|A.}}
{{Taxonbar|from=Q141637}}
{{Taxonbar|from=Q141637}}


⚫
[[Category:Early Cretaceous birds of Asia]]
[[Category:Bird genera]]
[[Category:Omnivoropterygidae]]
[[Category:Omnivoropterygidae]]
⚫
[[Category:Early Cretaceous dinosaurs of Asia]]
[[Category:Fossil taxa described in 2002]]
[[Category:Fossil taxa described in 2002]]

Latest revision as of 08:20, 15 October 2024

Sapeornis
Temporal range: Early Cretaceous, 124.5–120 Ma
↓
Fossil specimen, National Museum of Natural Science
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Avialae
Order: †Omnivoropterygiformes
Family: †Omnivoropterygidae
Genus: †Sapeornis
Zhou & Zhang, 2002
Species:
†S. chaoyangensis
Binomial name
†Sapeornis chaoyangensis
Zhou & Zhang, 2002
Synonyms
Genus synonymy
  • Didactylornis Yuan, 2008
  • Shenshiornis Hu, 2010
Species synonymy
  •  ?Omnivoropteryx sinousaorum Czerkas & Ji, 2002
  • Sapeornis angustis Zhou & Zhang, 2009
  • Didactylornis jii Yuan, 2008
  • Shenshiornis primita Hu, 2010[1]

Sapeornis is a monotypic genus of avialan dinosaurs which lived during the early Cretaceous period (late Barremian to early Aptian, roughly 125-120 mya). Sapeornis contains only one species, Sapeornis chaoyangensis.

Description

[edit]
Size of S. chaoyangensis compared with a human

Sapeornis was large for an early avialan, about 30–33 centimetres (0.98–1.08 ft) long in life, excluding the tail feathers.

The hand of Sapeornis was far more derived than that of Archaeopteryx. It had three fingers, the outer ones with two and the middle one with three phalanges, and a well-fused carpometacarpus. Its arms were about half again as long as the legs, suggesting a large wing area. On the other hand, its shoulder girdle was apparently ill-adapted to flapping flight and its furcula was unusual, with a hypocleidum similar to more advanced avialans but a general anatomy even more basal than in Archaeopteryx.[2] The humerus was large and bore holes, apparently to save weight, as in the Confuciusornithidae.

The skull has a handful of teeth in the upper jawtip only. Sapeornis had gastralia but no (or unossified) uncinate processes. The breastbone (sternum) was either absent or, more likely, made of cartilage rather than bone, as in more basal theropods.[3] The pygostyle was rod-like as in Confuciusornis and Nomingia, but like in the former there was no long bony tail anymore. While the tarsometatarsi were more fused than in Archaeopteryx, the fibula was long and reached the distal point of the tarsal joint, not reduced as in more modern birds (and some non-avian theropods like Avimimus). The first toe pointed backwards. In specimen IVPP V12375, the stomach contained numerous small gastroliths. Analysis of its skeletal bones suggest that it had an ontogeny and slow growth like Archaeopteryx and small carnivorous dinosaurs, rather than the explosively fast growth seen in modern birds.[4]

In absolute number of features shared with modern birds, S. chaoyangensis is about as derived as Confuciusornis. However, the apomorphies were largely different from Confuciusornis, and a character analysis demonstrates that these two were not closely related.[5] The tail plumage of Sapeornis consisted of rectrices that formed a graded, fan-like structure. The reduced fingers suggest that it might have had an alula. Not being well-adapted to flapping flight, Sapeornis probably was a glider and/or soarer that preferred more open country compared to the Enantiornithes and predominantly woodland birds, although it was able to perch on branches. The small gastroliths, overall large size, and the inferred habitat indicate that Sapeornis was most likely a herbivore, possibly eating plant seeds and fruits.[6]

Comparisons between the scleral rings of Sapeornis and modern birds and reptiles indicate that it may have been diurnal, similar to most modern birds.[7]

Discovery and history

[edit]
Holotype (IVPP V12698), Paleozoological Museum of China

Sapeornis is known from fossils found in Jiufotang Formation and Yixian Formation rocks in western Liaoning, China. These rocks formed during the late Aptian through early Albian epochs of the Cretaceous period, and are about 125-120 million years old. Several nearly complete skeletons have been found.[6]

The first known specimen (the type specimen) of Sapeornis was an incomplete skeleton dug up from Jiufotang Formation rocks in the area of Shangheshou, near Chaoyang City in Liaoning Province, China in the summer of 2000. It was discovered by a team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), and was reported in 2002 by the scientists Zhonghe Zhou and Fucheng Zhang.[8] They chose the name in honor of SAPE, the Society of Avian Paleontology and Evolution, which they combined with the Ancient Greek word όρνις (ornis), meaning "bird". The species name chaoyangensis is Latin for "from Chaoyang".[9] Soon after this, two more, nearly complete specimens were discovered in the Dapingfang area, about 40 kilometres (25 mi) from the original fossil site. None of these first three specimens preserved traces of feathers, but based on the size of their skeletons alone, they were recognized as the largest early Cretaceous avialans known at the time.[9]

In 2008, Yuan named a new specimen related to Sapeornis as Didactylornis jii. Yuan concluded that Didactylornis differed from Sapeornis in the proportions of the foot and number of wing and foot bones.[10] However, the relevant portions of the specimen were badly crushed, and later authors concluded that these differences were based on misinterpretation of the poorly preserved specimen. In a 2010 survey of Chinese avialan fossils, Li and colleagues considered Didactylornis a synonym of Sapeornis chaoyangensis.[11] In a 2012 study, Gao et al. concluded that Didactylornis was indeed a junior synonym of Sapeornis chaoyangensis, as were Shenshiornis and the supposed second species of Sapeornis, S. angustis.[12] Omnivoropteryx is also likely synonymous with Sapeornis.[13]

References

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  1. ^ Hu, D.; et al. (2010). "A new sapeornithid bird from China and its implication for early avian evolution". Acta Geologica Sinica. 84 (3): 472–482. Bibcode:2010AcGlS..84..472H. doi:10.1111/j.1755-6724.2010.00188.x. S2CID 86441777.
  2. ^ Senter, Phil (2006). "Scapular orientation in theropods and basal birds, and the origin of flapping flight" (PDF). Acta Palaeontologica Polonica. 51 (2): 305–313.
  3. ^ Foth, C. (2014). Comment on the absence of ossified sternal elements in basal paravian dinosaurs. Proceedings of the National Academy of Sciences, 111(50): E5334-E5334. doi:10.1073/pnas.1419023111
  4. ^ Erickson, Gregory M.; Rauhut, Oliver W. M.; Zhou, Zhonghe; Turner, Alan H.; Inouye, Brian D.; Hu, Dongyu; Norell, Mark A. (2009). "Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in Archaeopteryx". PLOS ONE. 4 (10): e7390. Bibcode:2009PLoSO...4.7390E. doi:10.1371/journal.pone.0007390. PMC 2756958. PMID 19816582.
  5. ^ Zhou, Zhonghe; Zhang, Fucheng (2006). "A beaked basal ornithurine bird (Aves, Ornithurae) from the Lower Cretaceous of China". Zool. Scripta. 35 (4): 363–373. doi:10.1111/j.1463-6409.2006.00234.x. S2CID 85222311.
  6. ^ a b Zhou, Zhonghe & Zhang, Fucheng (2003): Anatomy of the primitive bird Sapeornis chaoyangensis from the Early Cretaceous of Liaoning, China. Canadian Journal of Earth Sciences 40(5): 731–747. doi:10.1139/E03-011 (HTML abstract)
  7. ^ Schmitz, L.; Motani, R. (2011). "Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology". Science. 332 (6030): 705–8. Bibcode:2011Sci...332..705S. doi:10.1126/science.1200043. PMID 21493820. S2CID 33253407.
  8. ^ Zhou, Z.; Zhang, F. (2002). "Largest Bird from the Early Cretaceous and Its Implications for the Earliest Avian Ecological Diversification". Naturwissenschaften. 89 (1): 34–38. Bibcode:2002NW.....89...34Z. doi:10.1007/s00114-001-0276-9. PMID 12008971. S2CID 1116829.
  9. ^ a b Zhou, Z., & Zhang, F. (2003). Anatomy of the primitive bird Sapeornis chaoyangensis from the Early Cretaceous of Liaoning, China. Canadian Journal of Earth Sciences, 40(5): 731-747. doi:10.1139/E03-011
  10. ^ Yuan, C. (2008). "A new genus and species of Sapeornithidae from Lower Cretaceous in western Liaoning, China". Acta Geologica Sinica. 82 (1): 48–55. Bibcode:2008AcGlS..82...48Y. doi:10.1111/j.1755-6724.2008.tb00323.x. S2CID 86691693.
  11. ^ Li, D.; Sullivan, C.; Zhou, Z.; Zhang, Z. (2010). "Basal birds from China: a brief review". Chinese Birds. 1 (2): 83–96. doi:10.5122/cbirds.2010.0002. S2CID 84976296.
  12. ^ Gao, C.; Chiappe, L.M.; Zhang, F.; Pomeroy, D.L.; Shen, C.; Chinsamy, A.; Walsh, M.O. (2012). "A subadult specimen of the Early Cretaceous bird Sapeornis chaoyangensis and a taxonomic reassessment of sapeornithids". Journal of Vertebrate Paleontology. 32 (5): 1103–1112. Bibcode:2012JVPal..32.1103G. doi:10.1080/02724634.2012.693865. S2CID 86195304.
  13. ^ Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.
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