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{{Short description|Extinct order of reptiles}}
{{Automatic taxobox
{{Automatic taxobox
| name = Rhynchosaurs
| name = Rhynchosaurs
| fossil_range = [[Olenekian]]-[[Norian]]<br>~{{Fossil range|250|206}}
| fossil_range = [[Induan]]-early [[Norian]]{{Fossil range|Induan|Norian|}}
| image = Hyperodapedon BW2.jpg
| image = Hyperodapedon Exhibit Museum of Natural History.JPG
| image_caption = life restoration of ''[[Hyperodapedon]]''
| image_caption = Mounted skeleton model of ''[[Hyperodapedon]]''
| display_parents = 2
| taxon = Rhynchosauria
| taxon = Rhynchosauria
| authority = [[Henry Fairfield Osborn|Osborn]] [[1903 in paleontology|1903]]
| authority = [[Henry Fairfield Osborn|Osborn]] [[1903 in paleontology|1903]]
| subdivision_ranks = Subgroups
| subdivision_ranks = Subgroups
| subdivision = [[#Classification|See text]]
| subdivision = *{{extinct}}''[[Colobops]]''?
*{{extinct}}''[[Eohyosaurus]]''
*{{extinct}}''[[Howesia]]''
*{{extinct}}''[[Mesosuchus]]''
*{{extinct}}''[[Noteosuchus]]''
*{{extinct}}'''Rhynchosauridae'''
**{{extinct}}''[[Eifelosaurus]]''
**{{extinct}}''[[Rhynchosaurus]]''
**{{extinct}}'''Hyperodapedontidae'''
***{{extinct}}''[[Bentonyx]]''
***{{extinct}}''[[Fodonyx]]''
***{{extinct}}''[[Langeronyx]]''
***{{extinct}}'''[[Hyperodapedontinae]]'''
***{{extinct}}'''Stenaulorhynchinae'''
****{{extinct}}''[[Ammorhynchus]]''
****{{extinct}}''[[Brasinorhynchus]]''
****{{extinct}}''[[Elorhynchus]]''
****{{extinct}}''[[Mesodapedon]]''
****{{extinct}}''[[Stenaulorhynchus]]''
}}
}}


'''Rhynchosaurs''' were a group of [[Triassic]] [[diapsid]] [[reptile]]s from the group [[Archosauromorpha]], meaning they were distantly related to the [[Archosauria|archosaurs]].<ref>{{Cite journal|last=Ezcurra|first=Martín D.|last2=Montefeltro|first2=Felipe|last3=Butler|first3=Richard J.|date=2016|title=The Early Evolution of Rhynchosaurs|journal=Frontiers in Ecology and Evolution|language=English|volume=3|doi=10.3389/fevo.2015.00142|issn=2296-701X}}</ref>
'''Rhynchosaurs''' are a group of extinct herbivorous [[Triassic]] [[Archosauromorpha|archosauromorph]] [[reptile]]s, belonging to the order '''Rhynchosauria'''.<ref>{{Cite journal|last1=Ezcurra|first1=Martín D.|last2=Montefeltro|first2=Felipe|last3=Butler|first3=Richard J.|date=2016|title=The Early Evolution of Rhynchosaurs|journal=Frontiers in Ecology and Evolution|language=English|volume=3|doi=10.3389/fevo.2015.00142|issn=2296-701X|doi-access=free|hdl=11336/44040|hdl-access=free}}</ref> Members of the group are distinguished by their triangular skulls and elongated, beak like [[Premaxilla|premaxillary bones]]. Rhynchosaurs first appeared in the [[Early Triassic]], reaching their broadest abundance and a global distribution during the [[Carnian]] stage of the [[Late Triassic]].


== Description ==
== Description ==
[[File:Hyperodapedon sanjuanensis (2).png|left|thumb|Life restoration of ''[[Hyperodapedon sanjuanensis]]''.]]
[[File:Estauricossauro rincossauro.JPG|thumb|left|200px|[[Staurikosaurus]] and rhynchosaur]]
Rhynchosaurs were herbivores, and at times abundant (in some fossil localities accounting for 40 to 60% of specimens found), with stocky bodies and a powerful beak. Early primitive forms, like ''[[Mesosuchus]]'' and ''[[Howesia]]'', were generally small and more typically lizard-like in build, and had skulls rather similar to the early diapsid ''[[Youngina]]'', except for the beak and a few other features. Later and more advanced genera grew to medium to medium large size, up to two meters in length. The skull in these forms were short, broad, and triangular, becoming much wider than long in the most advanced forms like ''[[Hyperodapedon]]'' (= ''[[Scaphonyx]]''), with a deep cheek region, and the [[premaxilla]] extending outwards and downwards to form the upper beak. The broad skull would have accommodated powerful jaw muscles. The lower jaw was also deep, and when the mouth was closed it clamped firmly into the [[maxilla]] (upper jaw), like the blade of a [[penknife]] closing into its handle. This scissors-like action would have enabled rhynchosaurs to cut up tough plant material.
Rhynchosaurs were herbivores, and at times abundant (in some fossil localities accounting for 40 to 60% of specimens found), with stocky bodies and a powerful beak. Early primitive forms, like ''[[Mesosuchus]]'' and ''[[Howesia]]'', were generally small, typically lizard-like in build, and had skulls rather similar to the early diapsid ''[[Youngina]]'', except for the beak and a few other features. Later and more advanced genera grew to up to two meters in length. The skull in these forms were short, broad, and triangular, becoming much wider than long in the most advanced forms like ''[[Hyperodapedon]]'' (= ''[[Scaphonyx]]''), with a deep cheek region, and the [[premaxilla]] extending outwards and downwards to form the upper beak. The broad skull would have accommodated powerful jaw muscles. The lower jaw was also deep, and when the mouth was closed it clamped firmly into the [[maxilla]] (upper jaw), like the blade of a [[penknife]] closing into its handle. This scissors-like action would have enabled rhynchosaurs to cut up tough plant material. Rhynchosaur teeth had a unique condition known as '''ankylothecodonty''', similar to the [[acrodont]]y of modern [[tuatara]]s and some lizards but differing in the presence of deep roots.<ref>{{cite journal | url=https://onlinelibrary.wiley.com/doi/10.1111/pala.12654 | doi=10.1111/pala.12654 | title=Unique dentition of rhynchosaurs and their two‐phase success as herbivores in the Triassic | year=2023 | last1=Sethapanichsakul | first1=Thitiwoot | last2=Coram | first2=Robert A. | last3=Benton | first3=Michael J. | journal=Palaeontology | volume=66 | issue=3| doi-access=free }}</ref>


The teeth were unusual; those in the maxilla and palate were modified into broad tooth plates. The hind feet were equipped with massive claws, presumably for digging up roots and [[tuber]]s by backwards scratching of the hind limbs.
The teeth were unusual; those in the maxilla and palate were modified into broad tooth plates. The hind feet were equipped with massive claws, presumably for digging up roots and [[tuber]]s by backwards scratching of the hind limbs. Similar to [[elephant]]s, they had a fixed number of teeth. Those that were further back in the jaws replaced teeth that were worn out as the animal grew in size and the teeth were worn out because of a diet of very tough plants. In the end, they likely starved to death.<ref>[https://phys.org/news/2023-06-ancient-herbivore-diet-weakened-teeth.html Ancient herbivore's diet weakened teeth and lead to eventual starvation, suggests study]</ref>


Like many animals of this time, they had a worldwide distribution, being found across [[Pangea]]. These abundant animals might have died out suddenly at the end of the [[Carnian]] (Middle of the Late Triassic period), perhaps as a result of the extinction of the ''[[Dicroidium]]'' flora on which they may have fed. On the other hand, Spielmann, Lucas and Hunt (2013) described three distal ends of [[Humerus|humeri]] from early-mid [[Norian]] [[Bull Canyon Formation]] in [[New Mexico]], which they interpreted as bones of rhynchosaurs belonging to the species ''[[Otischalkia|Otischalkia elderae]]''; thus, the fossils might indicate that rhynchosaurs survived until the Norian.<ref>{{cite journal |author=Justin A. Spielmann |author2=Spencer G. Lucas |author3=Adrian P. Hunt |last-author-amp=yes |year=2013 |title=The first Norian (Revueltian) rhynchosaur: Bull Canyon Formation, New Mexico, U.S.A. |journal=New Mexico Museum of Natural History and Science Bulletin |volume=61 |pages=562–566 |url=http://paleo.cortland.edu/globaltriassic2/Bulletin%2061%20Final/43-Spielmann%20et%20al%20%28Rhynchos%29.pdf }}</ref>
Like many animals of this time, they had a worldwide distribution, being found across [[Pangea]]. These abundant animals might have died out suddenly at the end of the [[Carnian]] (Middle of the Late Triassic period), perhaps as a result of the extinction of the ''[[Dicroidium]]'' flora on which they may have fed. On the other hand, Spielmann, Lucas and Hunt (2013) described three distal ends of [[Humerus|humeri]] from early-mid [[Norian]] [[Bull Canyon Formation]] in [[New Mexico]], which they interpreted as bones of rhynchosaurs belonging to the species ''[[Otischalkia|Otischalkia elderae]]''; thus, the fossils might indicate that rhynchosaurs survived until the Norian.<ref>{{cite journal |author=Justin A. Spielmann |author2=Spencer G. Lucas |author3=Adrian P. Hunt |name-list-style=amp |year=2013 |title=The first Norian (Revueltian) rhynchosaur: Bull Canyon Formation, New Mexico, U.S.A. |url=https://www.researchgate.net/publication/280880846 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=61 |pages=562–566}}</ref> These fossils were later reinterpreted as belonging to [[Malerisaurinae|malerisaurine]] [[Azendohsauridae|azendohsaurids]].<ref>{{Cite journal |last=Nesbitt |first=Sterling J. |last2=Stocker |first2=Michelle R. |last3=Ezcurra |first3=Martín D. |last4=Fraser |first4=Nicholas C. |last5=Heckert |first5=Andrew B. |last6=Parker |first6=William G. |last7=Mueller |first7=Bill |last8=Sengupta |first8=Saradee |last9=Bandyopadhyay |first9=Saswati |last10=Pritchard |first10=Adam C. |last11=Marsh |first11=Adam D. |date=2022 |editor-last=Field |editor-first=Daniel |title=Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India |url=https://www.researchgate.net/publication/356929019 |journal=Papers in Palaeontology |language=en |volume=8 |issue=1 |doi=10.1002/spp2.1413 |issn=2056-2799}}</ref>


==Classification==
==Classification==


===Taxonomy===
===List of genera===


{| class="wikitable sortable" border="1"
{| class="wikitable sortable" border="1"
|-
|-
! colspan="7" align="center" |'''Genera'''
! colspan="6" align="center" |'''List of rhynchosaur genera'''
|-
|-
! Genus
! Genus
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|
|
[[Moenkopi Formation]]
[[Moenkopi Formation]]
| A stenaulorhynchine.
⚫
|-
⚫
|
''[[Beesiiwo]]''<ref name="Fitch2023">{{cite journal |last1=Fitch |first1=A. J. |last2=Haas |first2=M. |last3=C'Hair |first3=W. |last4=Ridgley |first4=E. |last5=Ridgley |first5=B. |last6=Oldman |first6=D. |last7=Reynolds |first7=C. |last8=Lovelace |first8=D. M. |title=A New Rhynchosaur Taxon from the Popo Agie Formation, WY: Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna |journal=Diversity |date=2023 |volume=15 |issue=4 |pages=544 |doi=10.3390/d15040544 |doi-access=free|hdl=10919/114487 |hdl-access=free }}</ref>
⚫
|
''B. cooowuse''
⚫
|
[[Carnian]]
⚫
|
{{Flag|US}} ([[Wyoming]])
|
|
⚫
[[Popo Agie Formation]]
| A hyperodapedontine previously referred to ''Hyperodapedon''.
|-
|-
|
|
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[[Santa Maria Formation]]
[[Santa Maria Formation]]
|
|
Previously known as the "Mariante Rhynchosaur".
A stenaulorhynchine, previously known as the "Mariante Rhynchosaur".
|-
|-
|
|
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|
|
[[Otter Sandstone Formation]]
[[Otter Sandstone Formation]]
| A basal hyperodapedontid.
⚫
|
⚫
|-
|''[[Elorhynchus]]''
|''E. carrolli''
|late [[Ladinian]]? - earliest [[Carnian]]?
⚫
|{{flag|Argentina}}
|[[Chañares Formation]] (''Tarjadia'' Assemblage Zone)
|A stenaulorhynchine.
|-
|-
|
|
''[[Eohyosaurus]]''<ref name=Eohyosaurus>{{Cite journal|author=Richard J. Butler|author2=Martín D. Ezcurra|author3=Felipe C. Montefeltro|author4=Adun Samathi|author5=Gabriela Sobral|last-author-amp=yes |year=2015 |title=A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria |journal=Zoological Journal of the Linnean Society |volume=174 |issue=3 |pages=571–588 |doi=10.1111/zoj.12246 }}</ref>
''[[Eohyosaurus]]''<ref name=Eohyosaurus>{{Cite journal|author=Richard J. Butler|author2=Martín D. Ezcurra|author3=Felipe C. Montefeltro|author4=Adun Samathi|author5=Gabriela Sobral|name-list-style=amp |year=2015 |title=A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria |journal=Zoological Journal of the Linnean Society |volume=174 |issue=3 |pages=571–588 |doi=10.1111/zoj.12246 |doi-access=free|hdl=11449/167867 |hdl-access=free }}</ref>
|
|
''E. wolvaardti''
''E. wolvaardti''
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|
{{Flag|South Africa}}
{{Flag|South Africa}}
|
|
[[Burgersdorp Formation]]
[[Burgersdorp Formation]] ([[Cynognathus Assemblage Zone|''Cynognathus'' Assemblage Zone]])
| A basal (non-rhynchosaurid) rhynchosaur.
⚫
|
|-
|-
|
|
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|
|
[[Otter Sandstone Formation]]
[[Otter Sandstone Formation]]
| A basal hyperodapedontid.
⚫
|
|-
|-
|
|
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|
|
{{Flag|South Africa}}
{{Flag|South Africa}}
|
|
[[Burgersdorp Formation]]
[[Burgersdorp Formation]] ([[Cynognathus Assemblage Zone|''Cynognathus'' Assemblage Zone]])
| A basal (non-rhynchosaurid) rhynchosaur.
⚫
|
|-
|-
| rowspan="6" |
| rowspan="6" |
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[[Lossiemouth Sandstone|Lossiemouth Sandstone Formation]]
[[Lossiemouth Sandstone|Lossiemouth Sandstone Formation]]
| rowspan="6" |
| rowspan="6" |
Six valid species has been named, the most of any rhynchosaur.
A hyperodapedontine, one of the most abundant and speciose rhynchosaur genera. Six valid species has been named, the most of any rhynchosaur.
|-
|-
|
|
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[[Carnian]]
[[Carnian]]
|
|
{{flag|Brazil}}<br/>
{{flag|Brazil}}<br />
{{flag|Argentina}}
{{flag|Argentina}}
|
|
[[Santa Maria Formation]]<br/>
[[Santa Maria Formation]]<br />
[[Ischigualasto Formation]]
[[Ischigualasto Formation]]
|-
|-
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[[Carnian]]
[[Carnian]]
|
|
{{flag|Argentina}}<br/>
{{flag|Argentina}}<br />
{{flag|Brazil}}
{{flag|Brazil}}
|
|
[[Ischigualasto Formation]]<br/>
[[Ischigualasto Formation]]<br />
[[Santa Maria Formation]]
[[Santa Maria Formation]]
|-
|-
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|
|
[[Makay Formation]] (Isalo II)
[[Makay Formation]] (Isalo II)
|A hyperodapedontine occasionally referred to ''Hyperodapedon''.
⚫
|
|-
|-
|
|
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|
|
[[Yerrapalli Formation]]
[[Yerrapalli Formation]]
| A stenaulorhynchine.
|
|-
|-
|
|
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|
|
[[Bromsgrove Sandstone Formation]]
[[Bromsgrove Sandstone Formation]]
|A basal hyperodapedontid.
|-
|-
|
|
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|
|
{{Flag|South Africa}}
{{Flag|South Africa}}
|
|
[[Burgersdorp Formation]]
[[Burgersdorp Formation]] ([[Cynognathus Assemblage Zone|''Cynognathus'' Assemblage Zone]])
| A basal (non-rhynchosaurid) rhynchosaur.
|
|-
|-
|
|
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|
|
{{Flag|South Africa}}
{{Flag|South Africa}}
|
|
[[Katberg Formation]]
[[Katberg Formation]] ([[Lystrosaurus Assemblage Zone|''Lystrosaurus'' Assemblage Zone]])
|
|
The earliest known species, and the only [[Early Triassic]] representative.<ref name=Eohyosaurus/>
A basal (non-rhynchosaurid) rhynchosaur. The earliest known species of rhynchosaur, and the only known [[Early Triassic]] representative.<ref name=Eohyosaurus/>
|-
|-
|
|
''[[Otischalkia]]''
''[[Oryctorhynchus]]''
|
|
''O. elderae''
''O. bairdi''
|
|
late [[Carnian]]
latest [[Carnian]]?-earliest [[Norian]]?
|
|
{{Flag|US}} ([[Texas]])
{{Flag|Canada}} ([[Nova Scotia]])
|
|
[[Dockum Group]]
[[Wolfville Formation]]
|A hyperodapedontine previously referred to ''Hyperodapedon''.
|
A ''[[nomen dubium]]''
|-
|-
|
|
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|
|
[[Tarporley Siltstone Formation]]
[[Tarporley Siltstone Formation]]
|A basal rhynchosaurid.
⚫
|
|-
|-
|
|
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|
|
[[Manda Formation]]
[[Manda Formation]]
|A stenaulorhynchine.
⚫
|
|-
|-
|
|
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|
|
Tunduru district
Tunduru district
|A hyperodapedontine previously referred to ''Hyperodapedon''.
|
|-
|-
|
|
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''T. sulcognathus''
''T. sulcognathus''
|
|
early [[Norian]]
late [[Carnian]] - early [[Norian]]
|
⚫
{{flag|Brazil}}
|
|
{{flag|Brazil}}<br />
⚫
[[Caturrita Formation]]
{{flag|Argentina}}
⚫
|
[[Caturrita Formation]]<br />
[[Ischigualasto Formation]]
|
|
The latest surviving species, and the only Norian rhynchosaur.
The latest surviving species, and the only rhynchosaur known with confidence to have survived into the Norian stage.
|-
|-
|}
|}


[[Image:Paradapedon 1DB.jpg|thumb|150px|right|''Hyperodapedon huxleyi (=Paradapedon)'']]
[[Image:Paradapedon 1DB.jpg|thumb|150px|right|''Hyperodapedon huxleyi'' (=''Paradapedon'')]]
[[Image:Mesosuchus BW.jpg|thumb|150px|right|''Mesosuchus browni'']]
[[Image:Mesosuchus BW.jpg|thumb|150px|right|''Mesosuchus browni'']]
[[Image:Rhynchosaurus articeps.jpg|thumb|150px|right|Skull of ''Rhynchosaurus articeps'']]
[[Image:Rhynchosaurus articeps.jpg|thumb|150px|right|Skull of ''Rhynchosaurus articeps'']]


===Phylogeny===
===Phylogeny===
[[Image:Crâno de Rincossauro - Museu Eça - Santa Maria.JPG|thumb|right|250px|Skull of a rhynchosaur, in [[Educational Museum Gama D'Eça]].]]
[[Image:Crâno de Rincossauro - Museu Eça - Santa Maria.JPG|thumb|right|250px|Skull of a rhynchosaur, in Educational Museum Gama D'Eça.]]
[[File:Hyperodapedon huxleyi maxilla.jpg|thumb|right|125px|Illustration of the ventral surface of a tooth plate of ''Hyperodapedon''.]]
[[File:Hyperodapedon huxleyi maxilla.jpg|thumb|right|125px|Illustration of the ventral surface of a tooth plate of ''Hyperodapedon''.]]


The Rhynchosauria included a single family, named Rhynchosauridae. All rhynchosaurs, apart from the four [[Early Triassic|Early]] and [[Middle Triassic]] monospecific genera, ''[[Eohyosaurus]]'', ''[[Mesosuchus]]'', ''[[Howesia]]'' and ''[[Noteosuchus]]'', are included in this family.<ref name=Eohyosaurus/> Hyperodapedontidae named by Lydekker (1885) was considered its [[junior synonym]].<ref name=cpd>{{cite journal |last=Benton |first=M. J. |year=1985 |title=Classification and phylogeny of the diapsid reptiles |journal=Zoological Journal of the Linnean Society |volume=84 |issue=2 |pages=97–164 |doi=10.1111/j.1096-3642.1985.tb01796.x}}</ref> However, Langer ''et al.'' (2000) noted that Hyperodapedontidae was erected by Lydekker to include ''[[Hyperodapedon]] gordoni'' and ''H. huxleyi'', clearly excluding ''[[Rhynchosaurus articeps]]'', which was the only other rhynchosaur known at that time. Thus, they defined it as the [[stem-based taxon]] that includes all rhynchosaurs more closely related to ''Hyperodapedon'' than to ''Rhynchosaurus''.<ref name=Langeretal>{{Cite journal|author1=Max C. Langer |author2=Cesar L. Schultz |lastauthoramp=yes |year=2000 |title=A new species of the Late Triassic rhynchosaur Hyperodapedon from the Santa Maria Formation of south Brazil |journal=Palaeontology |volume=43 |issue=6 |pages=633–652 |doi=10.1111/1475-4983.00143}}</ref>
The Rhynchosauria included a single family, named Rhynchosauridae. All rhynchosaurs, apart from the four [[Early Triassic|Early]] and [[Middle Triassic]] monospecific genera, ''[[Eohyosaurus]]'', ''[[Mesosuchus]]'', ''[[Howesia]]'' and ''[[Noteosuchus]]'', are included in this family.<ref name=Eohyosaurus/> Hyperodapedontidae named by Lydekker (1885) was considered its [[junior synonym]].<ref name=cpd>{{cite journal |last=Benton |first=M. J. |year=1985 |title=Classification and phylogeny of the diapsid reptiles |journal=Zoological Journal of the Linnean Society |volume=84 |issue=2 |pages=97–164 |doi=10.1111/j.1096-3642.1985.tb01796.x}}</ref> However, Langer ''et al.'' (2000) noted that Hyperodapedontidae was erected by Lydekker to include ''[[Hyperodapedon]] gordoni'' and ''H. huxleyi'', clearly excluding ''[[Rhynchosaurus articeps]]'', which was the only other rhynchosaur known at that time. Thus, they defined it as the [[stem-based taxon]] that includes all rhynchosaurs more closely related to ''Hyperodapedon'' than to ''Rhynchosaurus''.<ref name=Langeretal>{{Cite journal|author1=Max C. Langer |author2=Cesar L. Schultz |name-list-style=amp |year=2000 |title=A new species of the Late Triassic rhynchosaur Hyperodapedon from the Santa Maria Formation of south Brazil |journal=Palaeontology |volume=43 |issue=6 |pages=633–652 |doi=10.1111/1475-4983.00143|bibcode=2000Palgy..43..633L |s2cid=83566087}}</ref>


Within Hyperodapedontidae, which is now a subgroup of Rhynchosauridae, two subfamilies have been named. Stenaulorhynchinae named by Kuhn (1933) is defined sensu Langer and Schultz (2000) to include all species more closely related to ''[[Stenaulorhynchus]]'' than to ''Hyperodapedon''. Hyperodapedontinae named by Chatterjee (1969) was redefined by Langer ''et al.'' (2000) to include "all rhynchosaurs closer to ''Hyperodapedon'' than to ''"Rhynchosaurus" spenceri''" (now ''[[Fodonyx]]'').<ref name=Brasinorhynchus>{{cite journal |author=Cesar Leandro Schultz |author2=Max Cardoso Langer |author3=Felipe Chinaglia Montefeltro |last-author-amp=yes |year=2016 |title=A new rhynchosaur from south Brazil (Santa Maria Formation) and rhynchosaur diversity patterns across the Middle-Late Triassic boundary |journal=Paläontologische Zeitschrift |volume=in press |issue= 3|pages= 593–609|doi=10.1007/s12542-016-0307-7 |hdl=11449/161986 }}</ref>
Within Hyperodapedontidae, which is now a subgroup of Rhynchosauridae, two subfamilies have been named. Stenaulorhynchinae named by Kuhn (1933) is defined sensu Langer and Schultz (2000) to include all species more closely related to ''[[Stenaulorhynchus]]'' than to ''Hyperodapedon''. Hyperodapedontinae named by Chatterjee (1969) was redefined by Langer ''et al.'' (2000) to include "all rhynchosaurs closer to ''Hyperodapedon'' than to ''"Rhynchosaurus" spenceri''" (now ''[[Fodonyx]]'').<ref name=Brasinorhynchus>{{cite journal |author=Cesar Leandro Schultz |author2=Max Cardoso Langer |author3=Felipe Chinaglia Montefeltro |name-list-style=amp |year=2016 |title=A new rhynchosaur from south Brazil (Santa Maria Formation) and rhynchosaur diversity patterns across the Middle-Late Triassic boundary |journal=Paläontologische Zeitschrift |volume=90 |issue= 3|pages= 593–609|doi=10.1007/s12542-016-0307-7 |hdl=11449/161986 |s2cid=130644209 |hdl-access=free}}</ref>


The [[cladogram]] below is based on Schultz ''et al.'' (2016) which is the most genera inclusive rhynchosaur [[phylogenetic analysis]] to date,<ref name=Brasinorhynchus/> with the position of ''Noteosuchus'' taken from other recent analyses (since it was removed in Schultz ''et al.'' (2016)), all in consensus with one another.<ref name=Eohyosaurus/><ref name="ezcurra2016">Ezcurra MD. (2016) The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. ''PeerJ'', 4:e1778 [https://doi.org/10.7717/peerj.1778]</ref>
The [[cladogram]] below is based on Schultz ''et al.'' (2016) which is the most genera inclusive rhynchosaur [[phylogenetic analysis]] to date,<ref name=Brasinorhynchus/> with the position of ''Noteosuchus'' taken from other recent analyses (since it was removed in Schultz ''et al.'' (2016)), all in consensus with one another.<ref name=Eohyosaurus/><ref name="ezcurra2016">Ezcurra MD. (2016) The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. ''PeerJ'', 4:e1778 [https://doi.org/10.7717/peerj.1778]</ref>
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Latest revision as of 19:02, 3 August 2024

Rhynchosaurs
Temporal range: Induan-early Norian
Mounted skeleton model of Hyperodapedon
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Crocopoda
Order: †Rhynchosauria
Osborn 1903
Subgroups

Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria.[1] Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs first appeared in the Early Triassic, reaching their broadest abundance and a global distribution during the Carnian stage of the Late Triassic.

Description

[edit]
Life restoration of Hyperodapedon sanjuanensis.

Rhynchosaurs were herbivores, and at times abundant (in some fossil localities accounting for 40 to 60% of specimens found), with stocky bodies and a powerful beak. Early primitive forms, like Mesosuchus and Howesia, were generally small, typically lizard-like in build, and had skulls rather similar to the early diapsid Youngina, except for the beak and a few other features. Later and more advanced genera grew to up to two meters in length. The skull in these forms were short, broad, and triangular, becoming much wider than long in the most advanced forms like Hyperodapedon (= Scaphonyx), with a deep cheek region, and the premaxilla extending outwards and downwards to form the upper beak. The broad skull would have accommodated powerful jaw muscles. The lower jaw was also deep, and when the mouth was closed it clamped firmly into the maxilla (upper jaw), like the blade of a penknife closing into its handle. This scissors-like action would have enabled rhynchosaurs to cut up tough plant material. Rhynchosaur teeth had a unique condition known as ankylothecodonty, similar to the acrodonty of modern tuataras and some lizards but differing in the presence of deep roots.[2]

The teeth were unusual; those in the maxilla and palate were modified into broad tooth plates. The hind feet were equipped with massive claws, presumably for digging up roots and tubers by backwards scratching of the hind limbs. Similar to elephants, they had a fixed number of teeth. Those that were further back in the jaws replaced teeth that were worn out as the animal grew in size and the teeth were worn out because of a diet of very tough plants. In the end, they likely starved to death.[3]

Like many animals of this time, they had a worldwide distribution, being found across Pangea. These abundant animals might have died out suddenly at the end of the Carnian (Middle of the Late Triassic period), perhaps as a result of the extinction of the Dicroidium flora on which they may have fed. On the other hand, Spielmann, Lucas and Hunt (2013) described three distal ends of humeri from early-mid Norian Bull Canyon Formation in New Mexico, which they interpreted as bones of rhynchosaurs belonging to the species Otischalkia elderae; thus, the fossils might indicate that rhynchosaurs survived until the Norian.[4] These fossils were later reinterpreted as belonging to malerisaurine azendohsaurids.[5]

Classification

[edit]

List of genera

[edit]
List of rhynchosaur genera
Genus Species Age Location Unit Notes

Ammorhynchus

A. navajoi

Anisian

 US (Arizona)

Moenkopi Formation

A stenaulorhynchine.

Beesiiwo[6]

B. cooowuse

Carnian

 US (Wyoming)

Popo Agie Formation

A hyperodapedontine previously referred to Hyperodapedon.

Brasinorhynchus

B. mariantensis

Ladinian

 Brazil

Santa Maria Formation

A stenaulorhynchine, previously known as the "Mariante Rhynchosaur".

Bentonyx

B. sidensis

late Anisian

 UK (England)

Otter Sandstone Formation

A basal hyperodapedontid.
Elorhynchus E. carrolli late Ladinian? - earliest Carnian?  Argentina Chañares Formation (Tarjadia Assemblage Zone) A stenaulorhynchine.

Eohyosaurus[7]

E. wolvaardti

early Anisian

 South Africa

Burgersdorp Formation (Cynognathus Assemblage Zone)

A basal (non-rhynchosaurid) rhynchosaur.

Fodonyx

F. spenceri

late Anisian

 UK (England)

Otter Sandstone Formation

A basal hyperodapedontid.

Howesia

H. browni

early Anisian[7]

 South Africa

Burgersdorp Formation (Cynognathus Assemblage Zone)

A basal (non-rhynchosaurid) rhynchosaur.

Hyperodapedon

H. gordoni

Carnian

 UK (Scotland)

Lossiemouth Sandstone Formation

A hyperodapedontine, one of the most abundant and speciose rhynchosaur genera. Six valid species has been named, the most of any rhynchosaur.

H. huenei

Carnian

 Brazil

Santa Maria Formation

H. huxleyi

Carnian

 India

Lower Maleri Formation

H. mariensis

Carnian

 Brazil
 Argentina

Santa Maria Formation
Ischigualasto Formation

H. sanjuanensis

Carnian

 Argentina
 Brazil

Ischigualasto Formation
Santa Maria Formation

H. tikiensis

Carnian

 India

Tiki Formation

Isalorhynchus

I. genovefae

Carnian

 Madagascar

Makay Formation (Isalo II)

A hyperodapedontine occasionally referred to Hyperodapedon.

Mesodapedon

M. kuttyi

Anisian

 India

Yerrapalli Formation

A stenaulorhynchine.

Langeronyx

L. brodiei

Anisian

 UK (England)

Bromsgrove Sandstone Formation

A basal hyperodapedontid.

Mesosuchus

M. browni

early Anisian[7]

 South Africa

Burgersdorp Formation (Cynognathus Assemblage Zone)

A basal (non-rhynchosaurid) rhynchosaur.

Noteosuchus

N. colletti

early Induan

 South Africa

Katberg Formation (Lystrosaurus Assemblage Zone)

A basal (non-rhynchosaurid) rhynchosaur. The earliest known species of rhynchosaur, and the only known Early Triassic representative.[7]

Oryctorhynchus

O. bairdi

latest Carnian?-earliest Norian?

 Canada (Nova Scotia)

Wolfville Formation

A hyperodapedontine previously referred to Hyperodapedon.

Rhynchosaurus

R. articeps

Anisian

 UK (England)

Tarporley Siltstone Formation

A basal rhynchosaurid.

Stenaulorhynchus

S. stockleyi

late Anisian

 Tanzania

Manda Formation

A stenaulorhynchine.

Supradapedon

S. stockleyi

Middle - Late Triassic

 Tanzania

Tunduru district

A hyperodapedontine previously referred to Hyperodapedon.

Teyumbaita

T. sulcognathus

late Carnian - early Norian

 Brazil
 Argentina

Caturrita Formation
Ischigualasto Formation

The latest surviving species, and the only rhynchosaur known with confidence to have survived into the Norian stage.

Hyperodapedon huxleyi (=Paradapedon)
Mesosuchus browni
Skull of Rhynchosaurus articeps

Phylogeny

[edit]
Skull of a rhynchosaur, in Educational Museum Gama D'Eça.
Illustration of the ventral surface of a tooth plate of Hyperodapedon.

The Rhynchosauria included a single family, named Rhynchosauridae. All rhynchosaurs, apart from the four Early and Middle Triassic monospecific genera, Eohyosaurus, Mesosuchus, Howesia and Noteosuchus, are included in this family.[7] Hyperodapedontidae named by Lydekker (1885) was considered its junior synonym.[8] However, Langer et al. (2000) noted that Hyperodapedontidae was erected by Lydekker to include Hyperodapedon gordoni and H. huxleyi, clearly excluding Rhynchosaurus articeps, which was the only other rhynchosaur known at that time. Thus, they defined it as the stem-based taxon that includes all rhynchosaurs more closely related to Hyperodapedon than to Rhynchosaurus.[9]

Within Hyperodapedontidae, which is now a subgroup of Rhynchosauridae, two subfamilies have been named. Stenaulorhynchinae named by Kuhn (1933) is defined sensu Langer and Schultz (2000) to include all species more closely related to Stenaulorhynchus than to Hyperodapedon. Hyperodapedontinae named by Chatterjee (1969) was redefined by Langer et al. (2000) to include "all rhynchosaurs closer to Hyperodapedon than to "Rhynchosaurus" spenceri" (now Fodonyx).[10]

The cladogram below is based on Schultz et al. (2016) which is the most genera inclusive rhynchosaur phylogenetic analysis to date,[10] with the position of Noteosuchus taken from other recent analyses (since it was removed in Schultz et al. (2016)), all in consensus with one another.[7][11]

Rhynchosauria 

References

[edit]
  1. ^ Ezcurra, Martín D.; Montefeltro, Felipe; Butler, Richard J. (2016). "The Early Evolution of Rhynchosaurs". Frontiers in Ecology and Evolution. 3. doi:10.3389/fevo.2015.00142. hdl:11336/44040. ISSN 2296-701X.
  2. ^ Sethapanichsakul, Thitiwoot; Coram, Robert A.; Benton, Michael J. (2023). "Unique dentition of rhynchosaurs and their two‐phase success as herbivores in the Triassic". Palaeontology. 66 (3). doi:10.1111/pala.12654.
  3. ^ Ancient herbivore's diet weakened teeth and lead to eventual starvation, suggests study
  4. ^ Justin A. Spielmann; Spencer G. Lucas & Adrian P. Hunt (2013). "The first Norian (Revueltian) rhynchosaur: Bull Canyon Formation, New Mexico, U.S.A." New Mexico Museum of Natural History and Science Bulletin. 61: 562–566.
  5. ^ Nesbitt, Sterling J.; Stocker, Michelle R.; Ezcurra, Martín D.; Fraser, Nicholas C.; Heckert, Andrew B.; Parker, William G.; Mueller, Bill; Sengupta, Saradee; Bandyopadhyay, Saswati; Pritchard, Adam C.; Marsh, Adam D. (2022). Field, Daniel (ed.). "Widespread azendohsaurids (Archosauromorpha, Allokotosauria) from the Late Triassic of western USA and India". Papers in Palaeontology. 8 (1). doi:10.1002/spp2.1413. ISSN 2056-2799.
  6. ^ Fitch, A. J.; Haas, M.; C'Hair, W.; Ridgley, E.; Ridgley, B.; Oldman, D.; Reynolds, C.; Lovelace, D. M. (2023). "A New Rhynchosaur Taxon from the Popo Agie Formation, WY: Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna". Diversity. 15 (4): 544. doi:10.3390/d15040544. hdl:10919/114487.
  7. ^ a b c d e f Richard J. Butler; Martín D. Ezcurra; Felipe C. Montefeltro; Adun Samathi & Gabriela Sobral (2015). "A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria". Zoological Journal of the Linnean Society. 174 (3): 571–588. doi:10.1111/zoj.12246. hdl:11449/167867.
  8. ^ Benton, M. J. (1985). "Classification and phylogeny of the diapsid reptiles". Zoological Journal of the Linnean Society. 84 (2): 97–164. doi:10.1111/j.1096-3642.1985.tb01796.x.
  9. ^ Max C. Langer & Cesar L. Schultz (2000). "A new species of the Late Triassic rhynchosaur Hyperodapedon from the Santa Maria Formation of south Brazil". Palaeontology. 43 (6): 633–652. Bibcode:2000Palgy..43..633L. doi:10.1111/1475-4983.00143. S2CID 83566087.
  10. ^ a b Cesar Leandro Schultz; Max Cardoso Langer & Felipe Chinaglia Montefeltro (2016). "A new rhynchosaur from south Brazil (Santa Maria Formation) and rhynchosaur diversity patterns across the Middle-Late Triassic boundary". Paläontologische Zeitschrift. 90 (3): 593–609. doi:10.1007/s12542-016-0307-7. hdl:11449/161986. S2CID 130644209.
  11. ^ Ezcurra MD. (2016) The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ, 4:e1778 [1]

Bibliography

[edit]
[edit]

Data related to Rhynchosauria at Wikispecies

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