Chasmatosuchus

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Chasmatosuchus
Temporal range: Early Triassic, Olenekian
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Chasmatosuchus1DB.jpg
Life restoration of Chasmatosuchus rossicus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Family: Proterosuchidae
Subfamily: Chasmatosuchinae
Genus: Chasmatosuchus
Huene, 1940
Species
  • Chasmatosuchus rossicusHuene, 1940 (type)
  • ?†Chasmatosuchus vjushkoviOchev, 1961

Chasmatosuchus was an archosauriform reptile from the early Triassic period of European Russia. One of the earliest described archosauriforms, it was over 2 m long and is thought to have behaved like a modern crocodile. [1] 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. [2]

Life reconstruction of Chasmatosuchus. Chasmatosuchus by marciolcastro.jpg
Life reconstruction of Chasmatosuchus.

Chasmatosuchus was formerly assigned to Proterosuchidae, 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 and Jaikosuchus were found to be subjective junior synonyms of Chasmatosuchus. [3] 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. [4]

Chasmatosuchus parvus, based on an anterior cervical vertebra, was synonymized with Macrocnemus in 1995. [5]

Related Research Articles

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

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

Sarmatosuchus is an extinct genus of archosauriform reptile found in sediments of Middle Triassic age and known from the single species Sarmatosuchus otschevi. It is one of the earliest stem-archosaur species known. The holotype and only specimen was found in lithified river deposits of the Donguz Formation exposed near the Berdyanka River, Orenburg region, Russia. The genus was originally included in the extinct family Proterosuchidae. However, later analysis by David Gower and Andrei Sennikov, the describing author, has removed it from the Proterosuchidae and designated it a basal archosauriform.

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Jaikosuchus is an extinct genus of proterosuchid archosauriform. It contains a single species, J. magnus. Fossils have been found from European Russia that date back to the upper Olenekian stage of the Early Triassic.

Tsylmosuchus is an extinct genus of proterosuchid archosauriform reptile known from Western Russia. Fossils referred to Tsylmosuchus occurred over a wide area in sediments corresponding to the Induan and Olenekian stages of the Early Triassic. Most of these fossils are fragmentary neck vertebrae which were originally reported as sharing similarities with crocodile-line archosaurs (pseudosuchians) such as Mandasuchus. As a result, Tsylmosuchus was first described as part of the family Rauisuchidae, making it supposedly one of the oldest known archosaurs. However, its fragmentary remains do not show any of the distinguishing features of rauisuchids or even pseudosuchians in general, so Tsylmosuchus has more recently been interpreted as an indeterminate archosauriform. Although three species of Tsylmosuchus have been named, they lack diagnostic traits and are probably not distinct from each other. In 2023, Tsylmosuchus was reinterpreted as a proterosuchid, specifically a member of the subfamily Chasmatosuchinae.

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

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Exilisuchus is an extinct genus of archosauromorph reptile from the Early Triassic of Russia. The type species E. tubercularis was named in 1979. Fossils are known from two Russian assemblages, the Benthosuchus - Thoosuchus assemblage and the Angusaurus assemblage. Both are Olenekian in age. Although initially believed to be a proterosuchid archosauriform, a 2016 analysis found that it also shared features with tanystropheids, and thus is currently classified as Archosauromorpha incertae sedis. Due to the small amount of preserved material, this genus is sometimes considered a nomen dubium.

Gamosaurus is an extinct genus of proterosuchid archosauriform. It contains a single species, Gamosaurus lozovskii, named by Vitalii Georgievich Ochev in 1979.

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

Eorasaurus is an extinct genus of archosauromorph reptile known from the middle Late Permian of Tatarstan, European Russia. It contains a single species, Eorasaurus olsoni. When originally described by Sennikov (1997), Eorasaurus was identified as an early archosauromorph and assigned to the family Protorosauridae, Ezcurra et al. (2014) and Ezcurra (2016) later reclassified Eorasaurus and placed it within the group Archosauriformes. Eorasaurus is based solely on scant fossil material from the neck region, and is thus considered an unstable taxon in phylogenetic analyses. If Eorasaurus is an archosauriform, it would be the oldest known member of the group and would pre-date the previous record holder.

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References

  1. Paleobiology Database. PaleoDB. Accessed April 7, 2012.
  2. Chasmatosuchus Archived 2015-05-18 at the Wayback Machine . Vionto.com. Accessed April 7, 2012.
  3. 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
  4. Ezcurra, Martín D.; Bandyopadhyay, Saswati; Sengupta, Dhurjati P.; Sen, Kasturi; Sennikov, Andrey G.; Sookias, Roland B.; Nesbitt, Sterling J.; Butler, Richard J. (25 October 2023). "A new archosauriform species from the Panchet Formation of India and the diversification of Proterosuchidae after the end-Permian mass extinction". Royal Society Open Science. 10 (10). Bibcode:2023RSOS...1030387E. doi:10.1098/rsos.230387. ISSN   2054-5703. PMC   10598453 . PMID   37885992.
  5. Sennikov AG, 1995. Early thecodonts of Eastern Europe. Trudy Paleontologischeskogo Instituta RAN 263:1–141(in Russian).