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{{Short description|Extinct genus of dinosaurs}}
{{automatic taxobox
{{automatic taxobox
| image = Riojasaurus skull.jpg
| image = Riojasaurus skull.jpg
| image_width = 240px
| image_caption = ''Riojasaurus'' skull cast
| image_caption = ''Riojasaurus'' skull cast
| fossil_range = [[Late Triassic]], {{Fossil range|227|213}}
| fossil_range = [[Norian]]<br />~{{Fossil range|228|213}}
| taxon = Riojasaurus
|authority=[[José Bonaparte|Bonaparte]], 1967
| authority = [[José Bonaparte|Bonaparte]] 1969
|type species='''''R. incertus''''' <small>Bonaparte, 1967</small>
| type_species = {{extinct}}'''''Riojasaurus incertus'''''
| type_species_authority = [[José Bonaparte|Bonaparte]] 1969
}}
}}


'''''Riojasaurus''''' (meaning "Rioja lizard") was a [[herbivore|herbivorous]] [[sauropodomorph]] [[dinosaur]] named after [[La Rioja Province, Argentina|La Rioja Province]] in [[Argentina]] where it was found by [[José Bonaparte]]. It lived during the [[Late Triassic]] and grew to about {{convert|10|m|ft}} long.<ref name="ageofdinosaursriojasaurus">"Riojasaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 41. ISBN 0-7853-0443-6.</ref> ''Riojasaurus'' is the only known [[Riojasauridae|riojasaurid]] to live in South America.
'''''Riojasaurus''''' (meaning "lizard from [[La Rioja Province, Argentina|La Rioja]]") was a [[herbivore|herbivorous]] [[sauropodomorph]] [[dinosaur]] named after [[La Rioja Province, Argentina|La Rioja Province]] in [[Argentina]] where it was found in the [[Los Colorados Formation]] in the [[Ischigualasto-Villa Unión Basin]] by [[José Bonaparte]]. It lived during the [[Late Triassic]] ([[Norian]] stage) and grew to about {{convert|6.6|m|ft}} long.<ref name="ageofdinosaursriojasaurus">"Riojasaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 41. {{ISBN|0-7853-0443-6}}.</ref> ''Riojasaurus'' is the only known [[Riojasauridae|riojasaurid]] to live in South America.


== Discovery and naming ==
==Description==
''Riojasaurus incertus'' was named by [[José Bonaparte|Bonaparte]] (1969) and was based on the [[holotype]] specimen, PVL 3808, which was discovered in 1966 and consists of a postcranial skeleton which lacks the skull and mandibles, but preserves 6 presacral vertebrae, diverse caudals, both scapulae, the ischia, and the bones of the hand.<ref name=bonaparte67 /> In total, at least twenty specimens have been assigned to ''R. incertus'', and the first cranial material of ''R. incertus'' was discovered in 1987 and described in 1995.<ref name=bonaparte95 />
''Riojasaurus'' had a heavy body, bulky legs, and a long neck and tail. Its leg bones were dense and massive for an early sauropodomorph.<ref name="ageofdinosaursriojasaurus"/> By contrast, its vertebrae were lightened by hollow cavities, and unlike most early sauropodomorphs, ''Riojasaurus'' had four [[sacral vertebrae]] instead of three.<ref name="ageofdinosaursriojasaurus"/> It has been thought it probably moved slowly on all fours and was unable to rear up on its back legs.<ref name="ageofdinosaursriojasaurus"/><ref name="HeerdenGalton97">Van Heerden, J. and Galton, P.M. (1997). "The affinities of ''Melanorosaurus'' a Late Triassic prosauropod dinosaur from South Africa". ''Neues Jahrbuch für Geologie und Paläontologie Monatshefte''. (1):39-55</ref> The nearly equal length of the fore and hindlimbs<ref name="ageofdinosaursriojasaurus"/> has also been interpreted as suggestive of an obligatorily [[quadrupedal]] gait. However, in 2016, Scott Hartman found the hand anatomy, relatively straight back and largely immobile shoulder girdle of ''Riojasaurus'' supported it being a [[biped]].<ref>{{cite web|last1=Hartman|first1=Scott|title=La Rioja's ponderous biped|url=http://scotthartman.deviantart.com/art/La-Rioja-s-ponderous-biped-582857017}}</ref>


In 1994, 56 caudal vertebrae from one specimen, and a cast of the skull of ''Riojasaurus incertus'', along with several other specimens, were stolen from the [[National University of La Rioja]] in Argentina.<ref name="dml">Hultz, Thomas R. "Missing La Rioja Specimens." Missing La Rioja Specimens. N.p., 1994. Web. 05 Mar. 2017. <http://dml.cmnh.org/1994May/msg00010.html>.</ref> As of 2023, the whereabouts of the stolen fossils are unknown.
No skull was found with the first skeleton of ''Riojasaurus'',<ref name=bonaparte67>Bonaparte, J.F. (1967). Dos nuevas "faunas" de reptiles triásicos de Argentina. ''Ameghiniana'' 10(1): 89-102.</ref> although a well-preserved skull attributed to ''Riojasaurus'' was found later.<ref name=bonaparte95>Bonaparte, J.F. & Pumares, J.A. (1995). Notas sobre el primer craneo de ''Riojasaurus incertus'' (Dinosauria, Prosauropoda, Melanorosauridae) del Triasico Superios de La Rioja, Argentina. ''Ameghiniana'' 32(4): 341-349.</ref> The teeth of ''Riojasaurus'' were leaf shaped and serrated. The upper jaw contained 5 teeth at the front, with 24 more behind them in a row that ended under the eyes.

== Description ==
[[File:Riojasaurus Scale.svg|thumb|left|Size comparison]]
''Riojasaurus'' had a heavy body, bulky legs, and a long neck and tail. Its leg bones were dense and massive for an early sauropodomorph.<ref name="ageofdinosaursriojasaurus"/> In 2010 [[Gregory S. Paul]] estimated its length at {{convert|6.6|m|ft}} and its weight at {{convert|800|kg|lbs}}.<ref>{{Cite book|last=Paul|first=Gregory S.|title=The Princeton Field Guide to Dinosaurs|publisher=Princeton University Press|year=2010|location=New Jersey|pages=170}}</ref> Large individuals were estimated to have reached {{convert|10|m|ft}} long and weighed {{convert|3|MT|ST}}.<ref>{{cite journal |last=Seebacher |first=F. |date=2001 |url=https://dinoweb.ucoz.ru/_fr/4/A_new_method_to.pdf |title=A new method to calculate allometric length-mass relationships of dinosaurs |journal=Journal of Vertebrate Paleontology |volume=21 |issue=1 |pages=51–60|doi=10.1671/0272-4634(2001)021[0051:ANMTCA]2.0.CO;2 |jstor=4524171 |s2cid=53446536 }}</ref> By contrast, its vertebrae were lightened by hollow cavities, and unlike most early sauropodomorphs, ''Riojasaurus'' had four [[sacral vertebrae]] instead of three.<ref name="ageofdinosaursriojasaurus"/> It has been thought it probably moved slowly on all fours and was unable to rear up on its back legs.<ref name="ageofdinosaursriojasaurus"/><ref name="HeerdenGalton97">Van Heerden, J. and Galton, P.M. (1997). "The affinities of ''Melanorosaurus'' a Late Triassic prosauropod dinosaur from South Africa". ''Neues Jahrbuch für Geologie und Paläontologie - Monatshefte''. (1):39-55</ref> The nearly equal length of the fore and hindlimbs has also been interpreted as suggestive of an obligatorily [[quadrupedal]] gait,<ref name="ageofdinosaursriojasaurus"/> and the relative robustness of the forelimbs and hindlimbs is in the range of quadrupedal animals.<ref name="mcphee2018"/> However, the morphology of the hand and shoulder girdle has been interpreted as inconsistent with a quadrupedal gait.<ref name="hartman2016"/>

No skull was found with the first skeleton of ''Riojasaurus'',<ref name=bonaparte67>Bonaparte, J.F. (1969). Dos nuevas "faunas" de reptiles triásicos de Argentina. ''Ameghiniana'' 10(1): 89-102.</ref> although a well-preserved skull attributed to ''Riojasaurus'' was found later.<ref name=bonaparte95>Bonaparte, J.F. & Pumares, J.A. (1995). Notas sobre el primer craneo de ''Riojasaurus incertus'' (Dinosauria, Prosauropoda, Melanorosauridae) del Triasico Superios de La Rioja, Argentina. ''Ameghiniana'' 32(4): 341-349.</ref> The teeth of ''Riojasaurus'' were leaf shaped and serrated. The upper jaw contained 5 teeth at the front, with 24 more behind them in a row that ended under the eyes.


Comparisons between the [[sclerotic ring|scleral ring]]s of ''Riojasaurus'' and modern birds and reptiles suggest that it may have been [[cathemeral]], active throughout the day at short intervals.<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 }}</ref>
Comparisons between the [[sclerotic ring|scleral ring]]s of ''Riojasaurus'' and modern birds and reptiles suggest that it may have been [[cathemeral]], active throughout the day at short intervals.<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 }}</ref>


==Classification==
== Classification ==
[[File:Riojasaurus NT.jpg|thumb|left|Restoration]]
Many scientists think that ''Riojasaurus'' was closely related to ''[[Melanorosaurus]]'',<ref name="ageofdinosaursriojasaurus"/> known from the [[Triassic]]-[[Early Jurassic]] period. However, studies at [[Bristol University]], [[England]], suggest that it is unique in some key ways, such as the longer bones in its neck. It is certainly quite different from other sauropodomorphs found in the [[Los Colorados Formation]] of [[Argentina]].<ref>Moody, Richard. Dinofile. pg 20. Octopus Publishing Group Ltd., 2006</ref>
Many scientists think that ''Riojasaurus'' was closely related to ''[[Melanorosaurus]]'',<ref name="ageofdinosaursriojasaurus"/> known from the [[Triassic]]-[[Early Jurassic]] period. However, studies at [[Bristol University]], [[England]], suggest that it is unique in some key ways, such as the longer bones in its neck. It is certainly quite different from other sauropodomorphs found in the [[Los Colorados Formation]] of [[Argentina]].<ref>Moody, Richard. Dinofile. pg 20. Octopus Publishing Group Ltd., 2006</ref>
[[File:Riojasaurus size comparison v2.png|thumb|left|''Riojasaurus'', shown in comparison with humans.]]


Due to their size and limb anatomy ''Riojasaurus'' and the possibly related ''Melanorosaurus'' have been considered close relatives of the earliest [[sauropods]].<ref name="ageofdinosaursriojasaurus"/>
Due to their size and limb anatomy ''Riojasaurus'' and the possibly related ''Melanorosaurus'' have been considered close relatives of the earliest [[sauropods]].<ref name="ageofdinosaursriojasaurus"/>


==References==
== References ==
{{Reflist}}
{{Reflist|refs=
<ref name="hartman2016">{{cite web | last1 = Hartman | first1 = Scott | title=La Rioja's ponderous biped|url=http://scotthartman.deviantart.com/art/La-Rioja-s-ponderous-biped-582857017 | archive-url = https://web.archive.org/web/20210118084305/https://www.deviantart.com/drscotthartman/art/La-Rioja-s-ponderous-biped-582857017 | archive-date = 2021-01-18 | date = 2016-01-06 }}</ref>
<ref name="mcphee2018">{{Cite journal| doi = 10.1016/j.cub.2018.07.063| issn = 0960-9822| volume = 28| issue = 19| last1 = McPhee| first1 = Blair W.| last2 = Benson| first2 = Roger B.J.| last3 = Botha-Brink| first3 = Jennifer| last4 = Bordy| first4 = Emese M.| last5 = Choiniere| first5 = Jonah N.| title = A giant dinosaur from the earliest Jurassic of South Africa and the transition to quadrupedality in early sauropodomorphs| journal = Current Biology| date = 2018-09-27| pages = 3143–3151.e7| doi-access = free| pmid = 30270189| bibcode = 2018CBio...28E3143M}}</ref>
}}


== External links ==
{{Wikispecies|Riojasaurus}}
{{Wikispecies|Riojasaurus}}


{{Sauropodomorpha|S.}}
{{Portal|Dinosaurs}}
{{Taxonbar|from=Q131780}}
{{Portal bar|Dinosaurs}}


[[Category:Prosauropods]]
[[Category:Massopoda]]
[[Category:Dinosaur genera]]
[[Category:Norian life]]
[[Category:Late Triassic dinosaurs of South America]]
[[Category:Late Triassic dinosaurs of South America]]
[[Category:Fossil taxa described in 1967]]
[[Category:Fossils of Argentina]]
[[Category:Los Colorados Formation]]
[[Category:Fossil taxa described in 1969]]
[[Category:Taxa named by José Bonaparte]]
[[Category:Taxa named by José Bonaparte]]
[[Category:Sauropodomorphs of South America]]
[[Category:Late Triassic sauropodomorphs]]
[[Category:Monotypic sauropodomorph genera]]

Latest revision as of 13:06, 31 October 2024

Riojasaurus
Temporal range: Norian
~228–213 Ma
Riojasaurus skull cast
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Sauropodomorpha
Clade: Riojasauridae
Genus: Riojasaurus
Bonaparte 1969
Type species
Riojasaurus incertus

Riojasaurus (meaning "lizard from La Rioja") was a herbivorous sauropodomorph dinosaur named after La Rioja Province in Argentina where it was found in the Los Colorados Formation in the Ischigualasto-Villa Unión Basin by José Bonaparte. It lived during the Late Triassic (Norian stage) and grew to about 6.6 metres (22 ft) long.[1] Riojasaurus is the only known riojasaurid to live in South America.

Discovery and naming

[edit]

Riojasaurus incertus was named by Bonaparte (1969) and was based on the holotype specimen, PVL 3808, which was discovered in 1966 and consists of a postcranial skeleton which lacks the skull and mandibles, but preserves 6 presacral vertebrae, diverse caudals, both scapulae, the ischia, and the bones of the hand.[2] In total, at least twenty specimens have been assigned to R. incertus, and the first cranial material of R. incertus was discovered in 1987 and described in 1995.[3]

In 1994, 56 caudal vertebrae from one specimen, and a cast of the skull of Riojasaurus incertus, along with several other specimens, were stolen from the National University of La Rioja in Argentina.[4] As of 2023, the whereabouts of the stolen fossils are unknown.

Description

[edit]
Size comparison

Riojasaurus had a heavy body, bulky legs, and a long neck and tail. Its leg bones were dense and massive for an early sauropodomorph.[1] In 2010 Gregory S. Paul estimated its length at 6.6 metres (22 ft) and its weight at 800 kilograms (1,800 lb).[5] Large individuals were estimated to have reached 10 metres (33 ft) long and weighed 3 metric tons (3.3 short tons).[6] By contrast, its vertebrae were lightened by hollow cavities, and unlike most early sauropodomorphs, Riojasaurus had four sacral vertebrae instead of three.[1] It has been thought it probably moved slowly on all fours and was unable to rear up on its back legs.[1][7] The nearly equal length of the fore and hindlimbs has also been interpreted as suggestive of an obligatorily quadrupedal gait,[1] and the relative robustness of the forelimbs and hindlimbs is in the range of quadrupedal animals.[8] However, the morphology of the hand and shoulder girdle has been interpreted as inconsistent with a quadrupedal gait.[9]

No skull was found with the first skeleton of Riojasaurus,[2] although a well-preserved skull attributed to Riojasaurus was found later.[3] The teeth of Riojasaurus were leaf shaped and serrated. The upper jaw contained 5 teeth at the front, with 24 more behind them in a row that ended under the eyes.

Comparisons between the scleral rings of Riojasaurus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day at short intervals.[10]

Classification

[edit]
Restoration

Many scientists think that Riojasaurus was closely related to Melanorosaurus,[1] known from the Triassic-Early Jurassic period. However, studies at Bristol University, England, suggest that it is unique in some key ways, such as the longer bones in its neck. It is certainly quite different from other sauropodomorphs found in the Los Colorados Formation of Argentina.[11]

Due to their size and limb anatomy Riojasaurus and the possibly related Melanorosaurus have been considered close relatives of the earliest sauropods.[1]

References

[edit]
  1. ^ a b c d e f g "Riojasaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 41. ISBN 0-7853-0443-6.
  2. ^ a b Bonaparte, J.F. (1969). Dos nuevas "faunas" de reptiles triásicos de Argentina. Ameghiniana 10(1): 89-102.
  3. ^ a b Bonaparte, J.F. & Pumares, J.A. (1995). Notas sobre el primer craneo de Riojasaurus incertus (Dinosauria, Prosauropoda, Melanorosauridae) del Triasico Superios de La Rioja, Argentina. Ameghiniana 32(4): 341-349.
  4. ^ Hultz, Thomas R. "Missing La Rioja Specimens." Missing La Rioja Specimens. N.p., 1994. Web. 05 Mar. 2017. <http://dml.cmnh.org/1994May/msg00010.html>.
  5. ^ Paul, Gregory S. (2010). The Princeton Field Guide to Dinosaurs. New Jersey: Princeton University Press. p. 170.
  6. ^ Seebacher, F. (2001). "A new method to calculate allometric length-mass relationships of dinosaurs" (PDF). Journal of Vertebrate Paleontology. 21 (1): 51–60. doi:10.1671/0272-4634(2001)021[0051:ANMTCA]2.0.CO;2. JSTOR 4524171. S2CID 53446536.
  7. ^ Van Heerden, J. and Galton, P.M. (1997). "The affinities of Melanorosaurus a Late Triassic prosauropod dinosaur from South Africa". Neues Jahrbuch für Geologie und Paläontologie - Monatshefte. (1):39-55
  8. ^ McPhee, Blair W.; Benson, Roger B.J.; Botha-Brink, Jennifer; Bordy, Emese M.; Choiniere, Jonah N. (2018-09-27). "A giant dinosaur from the earliest Jurassic of South Africa and the transition to quadrupedality in early sauropodomorphs". Current Biology. 28 (19): 3143–3151.e7. Bibcode:2018CBio...28E3143M. doi:10.1016/j.cub.2018.07.063. ISSN 0960-9822. PMID 30270189.
  9. ^ Hartman, Scott (2016-01-06). "La Rioja's ponderous biped". Archived from the original on 2021-01-18.
  10. ^ 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.
  11. ^ Moody, Richard. Dinofile. pg 20. Octopus Publishing Group Ltd., 2006
[edit]