Opisthias

{{Short description|Extinct genus of reptiles}} {{Automatic taxobox | fossil_range = {{fossilrange|Kimmeridgian|Tithonian}} <small>Possible Berriasian record</small> | image = Opisthias rarus Gilmore, 1909.jpg | image_caption = Jaw of ''Opisthias rarus'' | taxon = Opisthias | authority = Gilmore 1909 | type_species = '''''Opisthias rarus''''' | type_species_authority = Gilmore, 1905<ref name="paleobackup.nceas.ucsb.edu">{{cite web | title = Opisthias Gilmore 1909 (rhynchocephalian) | url = https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=37820 | work = Paleobiology Database }}</ref> | subdivision_ranks = | subdivision = }}

'''''Opisthias''''' is a genus of sphenodont reptile. The type species, ''Opisthias rarus'', is known from the Late Jurassic (Kimmeridgian-Tithonian) of western North America.<ref name="vert-table">{{cite book | vauthors = Foster J | date = 2007 | chapter = Table 2.1: Fossil Vertebrates of the Morrison Formation. | title = Jurassic West: The Dinosaurs of the Morrison Formation and Their World. | publisher = Indiana University Press | pages = 58–59 }}</ref><ref name=":1">{{cite journal|last1=Herrera-Flores|first1=J.A.|last2=Stubbs|first2=T.L.|last3=Sour-Tovar|first3=F.|year=2022|title=Redescription of the type specimens for the Late Jurassic rhynchocephalian ''Opisthias rarus'' and a new specimen of ''Theretairus antiquus'' from Quarry 9, Morrison Formation, Wyoming, USA|journal=Acta Palaeontologica Polonica|volume=67|issue=3|pages=623–630|doi=10.4202/app.00929.2021|doi-access=free}}</ref>

==Distribution== left|thumb|A rhynchocephalian skull (DINO 16454) which has been attributed to ''Opisthias'' by some sources, but this has been disputed ''Opisthias'' is primarily known from remains found in the Late Jurassic of the United States, with remains found in the Morrison Formation (Colorado, Utah, and Wyoming),<ref name="vert-table" /><ref name=":1" /><ref name="paleobackup.nceas.ucsb.edu"/> present in stratigraphic zones 2 and 4–6.<ref name="foster-appendix">{{cite book |title=Jurassic West: The Dinosaurs of the Morrison Formation and Their World |vauthors=Foster J |date=2007 |publisher=Indiana University Press |pages=327–329 |chapter=Appendix}}</ref> Other remains suggested to be closely related to ''Opisthias'' are also known from the Late Jurassic Alcobaça Formation of Portugal.<ref>{{cite web | vauthors = Herrera-Flores JA, Stubbs TL | title = A re-evaluation of the taxonomy and diversity of the Late Jurassic sphenodontian Opisthias rarus Gilmore 1909 (Lepidosauria: Rhynchocephalia)[oral presentation]. | work = 13th Symposium on Mesozoic Terrestrial Ecosystems and Biota | date = July 2018 | url = https://www.researchgate.net/publication/347144125 }}</ref><ref>{{Cite journal |last1=Malafaia |first1=E. |last2=Ortega |first2=F. |last3=Escaso |first3=F. |last4=Dantas |first4=P. |last5=Pimentel |first5=N. |last6=Gasulla |first6=J. M. |last7=Ribeiro |first7=B. |last8=Barriga |first8=F. |last9=Sanz |first9=J. L. |date=2010 |title=Vertebrate fauna at the Allosaurus fossil-site of Andrés (Upper Jurassic), Pombal, Portugal |url=http://revistas.ucm.es/index.php/JIGE/article/view/JIGE1010220193A |journal=Journal of Iberian Geology |volume=36 |issue=2 |pages=193–204 |doi=10.5209/rev_JIGE.2010.v36.n2.7 |issn=1698-6180|doi-access=free |bibcode=2010JIbG...36..193M }}</ref> An undescribed crushed skull (DINO 16454) from the Morrison Formation has been attributed to this genus by some sources, though this has been strongly disputed by others.<ref>{{Cite journal |last1=DeMar |first1=David G. |last2=Jones |first2=Marc E. H. |last3=Carrano |first3=Matthew T. |date=2022-12-31 |title=A nearly complete skeleton of a new eusphenodontian from the Upper Jurassic Morrison Formation, Wyoming, USA, provides insight into the evolution and diversity of Rhynchocephalia (Reptilia: Lepidosauria) |journal=Journal of Systematic Palaeontology |language=en |volume=20 |issue=1 |article-number=2093139 |doi=10.1080/14772019.2022.2093139 |issn=1477-2019|doi-access=free |hdl=2440/136608 |hdl-access=free }}</ref>

A lower jaw is also known from the Berriasian aged Lulworth Formation of the United Kingdom, which appears to be distinct from the type North American species.<ref>{{Cite journal| vauthors = Herrera-Flores J |date=2020| veditors = Randall C | title=New insights on an enigmatic sphenodontian jaw from Dorset|url=https://www.researchgate.net/publication/347144049|journal=Proceedings of the Dorset Natural History and Archaeological Society|volume=141|pages=41–43|via=}}</ref> A fragmentary dentary possibly attributable to ''Opisthias'' is also known from the Berriasian aged Angeac-Charente bonebed in France.<ref name=":0">Ronan Allain, Romain Vullo, Lee Rozada, Jérémy Anquetin, Renaud Bourgeais, et al.. [https://hal.archives-ouvertes.fr/hal-03264773/document Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J/K boundary]. Geodiversitas, Museum National d'Histoire Naturelle Paris, In press. ffhal-03264773f</ref>

==Diet== ''Opisthias'' has been interpreted as a generalist, with its tooth morphology indicating had an ability to process plant material.<ref>{{cite journal | vauthors = Apesteguía S, Gómez RO, Rougier GW | title = The youngest South American rhynchocephalian, a survivor of the K/Pg extinction | journal = Proceedings. Biological Sciences | volume = 281 | issue = 1792 | article-number = 20140811 | date = October 2014 | pmid = 25143041 | pmc = 4150314 | doi = 10.1098/rspb.2014.0811 }}</ref>

==See also== {{Portal|Paleontology}} * Prehistoric reptile * Paleobiota of the Morrison Formation

==References== {{Reflist}}

Category:Morrison fauna Category:Jurassic lepidosaurs Category:Rhynchocephalia