View source for Rhynchosauria

{{Short description|Extinct order of reptiles}}
{{Automatic taxobox
| name = Rhynchosaurs
| fossil_range = [[Induan]]-early [[Norian]]{{Fossil range|Induan|Norian|}}
| image = Hyperodapedon Exhibit Museum of Natural History.JPG
| image_caption = Mounted skeleton model of ''[[Hyperodapedon]]''
| display_parents = 2
| taxon = Rhynchosauria
| authority = [[Henry Fairfield Osborn|Osborn]] [[1903 in paleontology|1903]]
| subdivision_ranks = Subgroups
| 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]]''
|synonyms=
*'''Gnathodontia''' {{small|Owen, 1859}}
}}

'''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 ==
[[File:Hyperodapedon sanjuanensis (2).png|left|thumb|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 [[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. They had a fixed number of teeth, and similar to [[elephant]]s, 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 |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==
{{Space|1}}

===List of genera===

{| class="wikitable sortable" border="1"
|-
! colspan="6" align="center" |'''List of rhynchosaur genera'''
|- 
! Genus
! Species
! Age
! Location
! Unit
! Notes
|-
| 
''[[Ammorhynchus]]''
|
''A. navajoi''
|
[[Anisian]]
| 
{{Flag|US}} ([[Arizona]])
| 
[[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''.
|-
| 
''[[Brasinorhynchus]]''
|
''B. mariantensis''
|
[[Ladinian]]
| 
{{Flag|Brazil}}
| 
[[Santa Maria Formation]]
|
A stenaulorhynchine, previously known as the "Mariante Rhynchosaur".
|-
| 
''[[Bentonyx]]''
|
''B. sidensis''
|
late [[Anisian]]
| 
{{Flag|UK}} ([[England]])
| 
[[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|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''
|
early [[Anisian]]
| 
{{Flag|South Africa}}
|
[[Burgersdorp Formation]] ([[Cynognathus Assemblage Zone|''Cynognathus'' Assemblage Zone]])
| A basal (non-rhynchosaurid) rhynchosaur.
|-
| 
''[[Fodonyx]]''
|
''F. spenceri''
|
late [[Anisian]]
| 
{{Flag|UK}} (England)
| 
[[Otter Sandstone Formation]]
| A basal hyperodapedontid.
|-
| 
''[[Howesia]]''
|
''H. browni''
|
early [[Anisian]]<ref name=Eohyosaurus/>
| 
{{Flag|South Africa}}
|
[[Burgersdorp Formation]] ([[Cynognathus Assemblage Zone|''Cynognathus'' Assemblage Zone]])
| A basal (non-rhynchosaurid) rhynchosaur.
|-
| rowspan="6" |
''[[Hyperodapedon]]''
|
''H. gordoni''
|
[[Carnian]]
| 
{{flag|UK}} ([[Scotland]])
|
[[Lossiemouth Sandstone|Lossiemouth Sandstone Formation]] 
| rowspan="6" |
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]]
| 
{{flag|Brazil}}
|
[[Santa Maria Formation]]
|-
|
''H. huxleyi''
|
[[Carnian]]
| 
{{flag|India}}
|
[[Lower Maleri Formation]]
|-
|
''H. mariensis''
|
[[Carnian]]
| 
{{flag|Brazil}}<br />
{{flag|Argentina}}
|
[[Santa Maria Formation]]<br />
[[Ischigualasto Formation]]
|-
|
''H. sanjuanensis''
|
[[Carnian]]
| 
{{flag|Argentina}}<br />
{{flag|Brazil}}
|
[[Ischigualasto Formation]]<br />
[[Santa Maria Formation]]
|-
|
''H. tikiensis''
|
[[Carnian]]
| 
{{flag|India}}
|
[[Tiki Formation]]
|-
| 
''[[Isalorhynchus]]''
|
''I. genovefae''
|
[[Carnian]]
|
{{flag|Madagascar}}
|
[[Makay Formation]] (Isalo II)
|A hyperodapedontine occasionally referred to ''Hyperodapedon''.
|-
| 
''[[Mesodapedon]]''
|
''M. kuttyi''
|
[[Anisian]]
| 
{{Flag|India}}
| 
[[Yerrapalli Formation]]
| A stenaulorhynchine.
|-
|
''[[Langeronyx]]''
|
''L. brodiei''
|
[[Anisian]]
|
{{Flag|UK}} (England)
|
[[Bromsgrove Sandstone Formation]]
|A basal hyperodapedontid.
|-
| 
''[[Mesosuchus]]''
|
''M. browni''
|
early [[Anisian]]<ref name=Eohyosaurus/>
| 
{{Flag|South Africa}}
|
[[Burgersdorp Formation]] ([[Cynognathus Assemblage Zone|''Cynognathus'' Assemblage Zone]])
| A basal (non-rhynchosaurid) rhynchosaur.
|-
| 
''[[Noteosuchus]]''
|
''N. colletti''
|
early [[Induan]]
| 
{{Flag|South Africa}}
|
[[Katberg Formation]] ([[Lystrosaurus Assemblage Zone|''Lystrosaurus'' Assemblage Zone]])
|
A basal (non-rhynchosaurid) rhynchosaur. The earliest known species of rhynchosaur, and the only known [[Early Triassic]] representative.<ref name=Eohyosaurus/>
|-
| 
''[[Oryctorhynchus]]''
|
''O. bairdi''
|
latest [[Carnian]]?-earliest [[Norian]]?
| 
{{Flag|Canada}} ([[Nova Scotia]])
| 
[[Wolfville Formation]]
|A hyperodapedontine previously referred to ''Hyperodapedon''.
|-
|
''[[Rhynchosaurus]]''
|
''R. articeps''
|
[[Anisian]]
|
{{Flag|UK}} (England)
|
[[Tarporley Siltstone Formation]]
|A basal rhynchosaurid.
|-
| 
''[[Stenaulorhynchus]]''
|
''S. stockleyi''
|
late [[Anisian]]
| 
{{flag|Tanzania}}
|
[[Manda Formation]]
|A stenaulorhynchine.
|-
| 
''[[Supradapedon]]''
|
''S. stockleyi''
|
[[Middle Triassic|Middle]] - [[Late Triassic]]
| 
{{flag|Tanzania}}
|
Tunduru district
|A hyperodapedontine previously referred to ''Hyperodapedon''.
|-
| 
''[[Teyumbaita]]''
|
''T. sulcognathus''
|
late [[Carnian]] - early [[Norian]]
|
{{flag|Brazil}}<br />
{{flag|Argentina}}
|
[[Caturrita Formation]]<br />
[[Ischigualasto Formation]]
|
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:Mesosuchus BW.jpg|thumb|150px|right|''Mesosuchus browni'']]
[[Image:Rhynchosaurus articeps.jpg|thumb|150px|right|Skull of ''Rhynchosaurus articeps'']]

===Phylogeny===
[[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''.]]

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 |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>

{{clade| style=font-size:85%;line-height:85%
|label1='''Rhynchosauria'''
|1={{clade
   |1=''[[Noteosuchus colletti]]''
   |2={{clade
      |1=''[[Mesosuchus browni]]''
      |2={{clade
         |1=''[[Howesia browni]]''
         |2={{clade
            |1=''[[Eohyosaurus wolvaardti]]''
            |label2='''Rhynchosauridae'''
            |2={{clade
               |1=''[[Rhynchosaurus articeps]]''
               |label2='''Hyperodapedontidae'''
               |2={{clade
                  |label1='''Stenaulorhynchinae'''
                  |1={{clade
                     |1=''[[Ammorhynchus navajoi]]''
                     |2=''[[Mesodapedon kuttyi]]''
                     |3={{clade
                        |1=''[[Brasinorhynchus mariantensis]]''
                        |2=''[[Stenaulorhynchus stockleyi]]''}} }}
                  |2={{clade
                     |1=''[[Bentonyx sidensis]]''
                     |2=''[[Langeronyx brodiei]]''
                     |3={{clade
                        |1=''[[Fodonyx spenceri]]''
                        |label2=[[Hyperodapedontinae]]
                        |2={{clade
                           |1=''[[Isalorhynchus genovefae]]''
                           |2={{clade
                              |1=''[[Teyumbaita sulcognathus]]''
                              |2=''[[Hyperodapedon]] spp.''}} }} }} }} }} }} }} }} }} }} }}

== References ==
{{Reflist}}

=== Bibliography ===
* [[Michael J. Benton|Benton, M. J.]] (2000), ''Vertebrate Paleontology'', 2nd ed. Blackwell Science Ltd.
* [[Robert L. Carroll|Carroll, R. L.]] (1988), ''Vertebrate Paleontology and Evolution'', W.H. Freeman & Co.
* [[David Dilkes|Dilkes, D. W.]] 1998. The Early Triassic rhynchosaur ''Mesosuchus browni'' and the interrelationships of basal archosauromorph reptiles. ''[[Philosophical Transactions of the Royal Society|Philosophical Transactions of the Royal Society of London: Biological Sciences]]'', 353:501-541.

== External links ==
* [http://www.ufrgs.br/paleovert/paleo/projeto/ Dinosaurs of Rio Grande do Sul, Brasil.]
{{Wikispecies-inline|Rhynchosauria}}

{{Rhynchosauria|R.}}
{{Taxonbar|from=Q131768}}

[[Category:Rhynchosauria| ]]
[[Category:Triassic reptiles]]
[[Category:Triassic taxonomic orders]]
[[Category:Anisian life]]
[[Category:Carnian life]]
[[Category:Norian life]]
[[Category:Olenekian life]]
[[Category:Early Triassic reptiles]]
[[Category:Middle Triassic reptiles]]
[[Category:Late Triassic reptiles]]
[[Category:Olenekian first appearances]]
[[Category:Norian extinctions]]