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Simbirskiasaurus; Temporal range: Early Cretaceous, 130 Ma
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Family:	†Ophthalmosauridae
Subfamily:	†Platypterygiinae
Genus:	†Simbirskiasaurus; Ochev and Efimov, 1985
Species
	S. birjukovi Ochev and Efimov, 1985 (Type);

Simbirskiasaurus is an extinct genus of ichthyosaur from the Early Cretaceous (early Barremian) of Ulyanovsk Oblast, Russia.^[1]^[2] Its type specimen is YKM 65119, a fragmentary skull and vertebral column.^[3]

Description

Fischer et al. give the diagnosis of Simbirskiasaurus as follows: "Platypterygiine ophthalmosaurid characterized by the following autapomorphies: external naris divided by a nasomaxillary pillar; posterior opening of the narial complex with anteroposteriorly constricted dorsal extension; deeply interdigitating prefrontal–lacrimal suture [reminiscent of the basal neoichthyosaurian Temnodontosaurus platyodon (Conybeare, 1822); see Godefroit, 1993]. Simbirskiasaurus birjukovi is also characterized by the following unique combination of features: subnarial process of the premaxilla reaches the posterior margin of the external naris (shared with Cryopterygius kristiansenae Druckenmiller et al., 2012); elongated anterior process of the maxilla, reaching anteriorly the level of the nasal [unlike in Aegirosaurus leptospondylus Bardet & Fernández, 2000 and Sveltonectes insolitus (Fischer et al., 2011b)]; pres- ence of a supranarial process of the premaxilla [shared with Platypterygius australis (McCoy, 1867), see Kear, 2005, and possibly Pervushovisaurus bannovkensis (Arkhangelsky, 1998b)]."^[2]

Phylogeny

The following cladogram shows a possible phylogenetic position of Simbirskiasaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).^[4]

Ophthalmosauria

Ophthalmosaurinae

Acamptonectes densus

Mollesaurus periallus

	Ophthalmosaurus natans

	Ophthalmosaurus icenicus

Gengasaurus nicosiai

Nannopterygius yasykovi

	Nannopterygius enthekiodon

	Nannopterygius saveljeviensis

	Nannopterygius borealis

Arthropterygius volgensis

Arthropterygius lundi

Arthropterygius thalassonotus

	Arthropterygius hoybergeti

	Arthropterygius chrisorum

Platypterygiinae

Brachypterygius extremus

Aegirosaurus leptospondylus

Muiscasaurus catheti

Leninia stellans

Sveltonectes insolitus

Athabascasaurus bitumineus

Platypterygius americanus

	Acuetzpalin carranzai

	Platypterygius sachicarum

	Caypullisaurus bonapartei

	Grendelius mordax

	Grendelius alekseevi

	Grendelius pseudoscythicus

	Grendelius zhuravlevi

Undorosaurus kielanae

	Undorosaurus nessovi

	Undorosaurus gorodischensis

Platypterygius australis

	Plutoniosaurus bedengensis

	Simbirskiasaurus birjukovi

	Platypterygius hercynicus

	Sisteronia seeleyi

	Platypterygius platydactylus

	Maiaspondylus lindoei

References

^ Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (entry on Reptilia)". Bulletins of American Paleontology. 364: 560. Retrieved 2008-09-28.
^ ^a ^b Valentin Fischer, Maxim S. Arkhangelsky, Darren Naish, Ilya M. Stenshin, Gleb N. Uspensky and Pascal Godefroit (2014) Simbirskiasaurus and Pervushovisaurus reassessed: implications for the taxonomy and cranial osteology of Cretaceous platypterygiine ichthyosaurs. Zoological Journal of the Linnean Society 171(4): 822–841. http://onlinelibrary.wiley.com/doi/10.1111/zoj.12158/abstract
^ Storrs, G. W., M. S. Arkhangel'skii and V. M. Efimov. 2000. Mesozoic marine reptiles of Russia and other former Soviet republics. pages 187-210 In Benton, M. J., M. A. Shiskin, D. M. Unwin and E. N. Kurochkin, (eds.), The Age of Dinosaurs in Russia and Mongolia, Cambridge University Press, Cambridge.
^ Nikolay G. Zverkov & Megan L. Jacobs (2021) [2020]. "Revision of Nannopterygius (Ichthyosauria: Ophthalmosauridae): reappraisal of the 'inaccessible' holotype resolves a taxonomic tangle and reveals an obscure ophthalmosaurid lineage with a wide distribution". Zoological Journal of the Linnean Society. 191 (1): 228–275. doi:10.1093/zoolinnean/zlaa028.