Opisthiamimus (lit. 'Opisthias mimic') 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 (the length from the tip of the snout to the cloaca) 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.[1]
| Opisthiamimus Temporal range:
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| Restored skull in lateral view | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Rhynchocephalia |
| Infraorder: | Eusphenodontia |
| Genus: | †Opisthiamimus DeMar, Jones & Carrano, 2022 |
| Type species | |
| †Opisthiamimus gregori DeMar, Jones & Carrano, 2022[1]
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Phylogeny
editCladogram following Sues and Schoch, 2023:[2]
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References
edit- ^ a b DeMar, D. G.; Jones, M. E. H.; Carrano, M. T. (2022). "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): 779–786. doi:10.1080/14772019.2022.2093139. hdl:2440/136608. PMID 2093139.
- ^ Sues, Hans-Dieter; Schoch, Rainer R. (2023-11-07). "The oldest known rhynchocephalian reptile from the Middle Triassic (Ladinian) of Germany and its phylogenetic position among Lepidosauromorpha". The Anatomical Record. doi:10.1002/ar.25339. ISSN 1932-8486. PMID 37937325. S2CID 265050255.