''Chasmatosuchus'' was an archosauriform reptile from the early

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

period of

European Russia European Russia is the western and most populated part of the Russia, Russian Federation. It is geographically situated in Europe, as opposed to the country's sparsely populated and vastly larger eastern part, Siberia, which is situated in Asia ...

. One of the earliest described archosauriforms, it was over 2 m long and is thought to have behaved like a modern

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large, semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term "crocodile" is sometimes used more loosely to include ...

. Its mouth had two distinct features: the top of its jaw hooked downwards to aid in holding prey, and the upper palate was lined with a row of teeth—a primitive feature lost in later

archosaurs Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

''Chasmatosuchus'' was formerly assigned to

Proterosuchidae Proterosuchidae is an early family of basal archosauriforms whose fossils are known from the Late Permian and the Early Triassic. The highest diversity of genera is known from European Russia, but fossils are also known from South Africa, India ...

, but a 2016 cladistic analysis by Martin Ezcurra could not confidently place the species of ''Chasmatosuchus'' within Proterosuchidae. Instead their position was found to be unresolved due to the fragmentary nature of the known material, however ''Chasmatosuchus'' is more likely to be intermediate between proterosuchids and erythrosuchids and possibly closely related to '' Sarmatosuchus otschevi'' and '' Cuyosuchus huenei''. Ezcurra (2016) could only place ''C. rossicus'' and ''C. magnus'' within ''Chasmatosuchus'' with certainty, while the third valid species'' "C." vjushkovi'' potentially does not belong to ''Chasmatosuchus'' and may represent a proterosuchid. ''

Gamosaurus ''Gamosaurus'' is an extinct genus of Proterosuchidae, proterosuchid Archosauriformes, archosauriform. It contains a single species, ''Gamosaurus lozovskii'', named by Vitalii Georgievich Ochev in 1979 in paleontology, 1979. Discovery and expla ...

'' and '' Jaikosuchus'' were found to be subjective

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

s of ''Chasmatosuchus''.Ezcurra, M.D. (2016),The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ4:e1778;DOI10.7717/peerj.1778 However, a 2023 study, also by Ezcurra ''et al'', found ''Chasmatosuchus'' to be a true proterosuchid, distinct from ''Gamosaurus'' and ''Jaikosuchus'' based on vertebral differences, and that all three belonged to a new subfamily of the Proterosuchidae, the

Chasmatosuchinae Proterosuchidae is an early family of Basal (phylogenetics), basal archosauriformes, archosauriforms whose fossils are known from the Lopingian, Late Permian and the Early Triassic. The highest diversity of genera is known from European Russia, b ...

. ''Chasmatosuchus parvus'', based on an anterior cervical vertebra, was synonymized with '' Macrocnemus'' in 1995.Sennikov AG, 1995. Early thecodonts of Eastern Europe. Trudy Paleontologischeskogo Instituta RAN 263:1–141(in Russian).

References

Proterosuchidae Early Triassic reptiles of Europe Fossil taxa described in 1940 Prehistoric reptile genera {{triassic-reptile-stub