Opisthias

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Opisthias
Temporal range: Kimmeridgian–Tithonian
O
S
D
C
P
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J
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Pg
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Possible Berriasian record
Opisthias rarus Gilmore, 1909.jpg
Jaw of Opisthias rarus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Rhynchocephalia
Clade: Opisthodontia
Genus: Opisthias
Gilmore 1909
Type species
Opisthias rarus
Gilmore, 1905 [1]

Opisthias is a genus of sphenodont reptile. The type species, Opisthias rarus, is known from the Late Jurassic (Kimmeridgian-Tithonian) of western North America. [2] [3]

Contents

Distribution

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), [2] [3] [1] present in stratigraphic zones 2 and 4–6. [4] Other remains suggested to be closely related to Opisthias are also known from the Late Jurassic Alcobaça Formation of Portugal. [5] [6] A undescribed crushed skull (DINO 16454) from the Morrison Formaiton has been attributed to this genus by some sources, though this has been strongly disputed by others. [7]

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. [8] A fragmentary dentary possibly attributable to Opisthias is also known from the Berriasian aged Angeac-Charente bonebed in France. [9]

Diet

Opisthias has been interpreted as a generalist, with its tooth morphology indicating had an ability to process plant material. [10]

See also

Related Research Articles

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The Lepidosauria is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes lizards and snakes. Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian reptiles in the present day. Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era. However, it is represented by only one living species: the tuatara, a superficially lizard-like reptile native to New Zealand.

<span class="mw-page-title-main">Rhynchocephalia</span> Order of reptiles

Rhynchocephalia is an order of lizard-like reptiles that includes only one living species, the tuatara of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a speciose group with high morphological and ecological diversity. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved a worldwide distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria.

<span class="mw-page-title-main">Sphenodontidae</span> Family of reptiles

Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara. Historically the taxa included within Sphenodontidae have varied greatly between analyses, and the group has lacked a formal definition. Cynosphenodon from the Jurassic of Mexico has consistently been recovered as a close relative of the tuatara in most analyses, with the clade containing the two and other very close relatives of the tuatara often called Sphenodontinae. The herbivorous Eilenodontinae, otherwise considered part of Opisthodontia, is considered to be part of this family in many recent studies as the sister group to Sphenodontinae. The earliest Sphenodontines are known from the Early Jurassic of North America, with other remains known from the Late Jurassic of Europe, the Late Cretaceous of South America and the Miocene-recent of New Zealand. Sphenodontines are characterised by a complete lower temporal bar caused by the fusion of a forward directed process (extension) of the quadrate/quadratojugal and the jugal, which was an adaptation for reducing stress in the skull during hard biting. Other synapomorphies of Sphenodontinae include the presence of nasal foramina, a posterodorsal process of the coronoid of the lower jaw, the present of caniniform successional teeth at the front of the jaws, the presence of flanges on the posterior parts of teeth at back of the lower jaw, and an expanded radial condyle on the humerus. Like modern tuatara, members of Sphenodontinae were likely generalists with a carnivorous/insectivorous diet.

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<i>Homoeosaurus</i> Extinct genus of reptiles

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<i>Clevosaurus</i> Extinct genus of reptiles

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Cynosphenodon is an extinct genus of rhynchocephalian in the family Sphenodontidae from the Middle Jurassic La Boca Formation of Tamaulipas, Mexico. It is known from a largely complete lower jaw and fragments of the upper jaw. It is suggested to be among the closest known relatives of the tuatara, with both being placed in the Sphenodontinae, which is supported by among other characters, the growth pattern of the teeth.

Theretairus is a Late Jurassic genus of sphenodont reptile from the Morrison Formation of western North America, present in stratigraphic zones 5 and 6.

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Cteniogenys is a genus of choristodere, a morphologically diverse group of aquatic reptiles. It is part of the monotypic family Cteniogenidae. The type and only named species, C. antiquus, was named in 1928 by Charles W. Gilmore. The holotype, VP.001088, was collected in the Morrison Formation, Wyoming in 1881 by William H. Reed. More specimens have been discovered since then, including specimens from the Late Jurassic of Portugal and Middle Jurassic of Britain, which have not been assigned to species.

Paramacellodus is an extinct genus of scincomorph lizards from the Early Cretaceous of England and France, and the Late Jurassic of Portugal and the western United States. The type species, Paramacellodus oweni, was named in 1967 from the earliest Cretaceous (Berriasian) Purbeck Group in Dorset, England. Additional material referable to a species of Paramacellodus, possibly P. oweni, has been described from the Morrison Formation, specifically in Como Bluff, Wyoming, and Dinosaur National Monument, Utah. An indeterminate species is known from the Berriasian aged Angeac-Charente bonebed in France. Paramacellodus belongs to an extinct family of scincomorphs called Paramacellodidae, which spanned most of Laurasia during the Late Jurassic and Early Cretaceous and represented one of the earliest evolutionary radiations of lizards.

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<span class="mw-page-title-main">Opisthodontia (reptile)</span> Clade of reptiles

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<span class="mw-page-title-main">Clevosaurs</span> Family of reptiles

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<span class="mw-page-title-main">Sapheosaur</span> Extinct group of reptiles

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Opisthiamimus is an extinct genus of small-bodied eusphenodontian rhynchocephalian from the Upper Jurassic Morrison Formation of Northern Wyoming, United States. The type species, O. gregori, is known from four specimens, which together preserve a nearly complete skeleton. It is amongst the smallest known rhynchocephalians, with a skull length of 2.05 centimetres (0.81 in) and a snout–vent length of around 8.5 centimetres (3.3 in). The genus was described in 2022 by David DeMar, Marc E. H. Jones, and Matthew Carrano. It was found that it was only distantly related to Eilenodon, Theretairus and Opisthias, the other known rhynchocephalians from the Morrison Formation.

References

  1. 1 2 "Opisthias Gilmore 1909 (rhynchocephalian)". Paleobiology Database.
  2. 1 2 Foster J (2007). "Table 2.1: Fossil Vertebrates of the Morrison Formation.". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 58–59.
  3. 1 2 Herrera-Flores, J.A.; Stubbs, T.L.; Sour-Tovar, F. (2022). "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". Acta Palaeontologica Polonica. 67 (3): 623–630. doi: 10.4202/app.00929.2021 .
  4. Foster J (2007). "Appendix". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327–329.
  5. Herrera-Flores JA, Stubbs TL (July 2018). "A re-evaluation of the taxonomy and diversity of the Late Jurassic sphenodontian Opisthias rarus Gilmore 1909 (Lepidosauria: Rhynchocephalia)[oral presentation]". 13th Symposium on Mesozoic Terrestrial Ecosystems and Biota.
  6. Malafaia, E.; Ortega, F.; Escaso, F.; Dantas, P.; Pimentel, N.; Gasulla, J. M.; Ribeiro, B.; Barriga, F.; Sanz, J. L. (2010). "Vertebrate fauna at the Allosaurus fossil-site of Andrés (Upper Jurassic), Pombal, Portugal". Journal of Iberian Geology. 36 (2): 193–204. Bibcode:2010JIbG...36..193M. doi: 10.5209/rev_JIGE.2010.v36.n2.7 . ISSN   1698-6180.
  7. DeMar, David G.; Jones, Marc E. H.; Carrano, Matthew T. (2022-12-31). "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 of Systematic Palaeontology. 20 (1): 2093139. doi: 10.1080/14772019.2022.2093139 . hdl: 2440/136608 . ISSN   1477-2019.
  8. Herrera-Flores J (2020). Randall C (ed.). "New insights on an enigmatic sphenodontian jaw from Dorset". Proceedings of the Dorset Natural History and Archaeological Society. 141: 41–43.
  9. Ronan Allain, Romain Vullo, Lee Rozada, Jérémy Anquetin, Renaud Bourgeais, et al.. 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
  10. Apesteguía S, Gómez RO, Rougier GW (October 2014). "The youngest South American rhynchocephalian, a survivor of the K/Pg extinction". Proceedings. Biological Sciences. 281 (1792): 20140811. doi:10.1098/rspb.2014.0811. PMC   4150314 . PMID   25143041.