Tsylmosuchus

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Tsylmosuchus
Temporal range: Early Triassic Induan–Olenekian
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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: Tsylmosuchus
Sennikov, 1990
Species
  • T. jakovleviSennikov, 1990 (type)
  • T. samarensisSennikov, 1990
  • T. donensisSennikov, 1990
Synonyms [1]

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. [2] [3] [4] 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. [5] In 2023, Tsylmosuchus was reinterpreted as a proterosuchid, specifically a member of the subfamily Chasmatosuchinae. [6]

Discovery

The genus is named after the Tsilma River, near where fossils have been found. Three species were named along with the original genus in 1990, their holotypes each comprising a single cervical (neck) vertebra and all of them only tentatively differentiated by their ages. [3] [2] The holotype of the type species T. jakovlevi was found near Ust'-Tsylma in the Komi Republic. This specimen and other referred material (such as ilia) come from the Mezen' and Pechora river basins, which preserve sediments of the Sludkian and Ustmylian gorizonts (early Olenekian). Some material once referred to the proterosuchid Chasmatosuchus magnus has since been referred to this species. [3] [2] T. donensis comes from the Donskaya Luka site in Volgograd Oblast, which preserves the Lipovskaya Formation of the Yarenskain Gorizont (Upper Olenekian).

Tsylmosuchus samariensis, described from a single site in Borskoi (Samara Oblast, along the Obshchy Syrt) dating to the Rybinskian Gorizont (Induan), was synonymized with Chasmatosuchus rossicus by Ezcurra (2016), who also made the Tsylmosuchus type species a nomen dubium. [7] However, in 2023, Ezcurra reversed this decision and placed all three species in Tsylmosuchus again, and found the genus to be a proterosuchid. [6]

Description

Tsylmosuchus is known primarily from vertebrae. These vertebrae have been compared to "rauisuchid" vertebrae, from the Manda Beds of Tanzania, which are now referred to Mandasuchus . Like several contemporary "rauisuchians" ( Energosuchus and Vytshegdosuchus ), Tsylmosuchus has elongated cervical vertebrae. This would have given it a relatively long neck. [3]

Nesbitt (2009) suggested that elongated cervical vertebrae were present in numerous archosauriform clades, and that the length of the cervical vertebrae depended on the position in the presacral column, as seen in the poposauroid Arizonasaurus and the non-archosaurian archosauriform Guchengosuchus . The holotypes of each of the three species consist of a single cervical vertebra, which does not bear any other clear autapomorphies. Furthermore, the material referred to these species cannot be shown to belong to the same taxa as the holotypes. Thus, Nesbitt (2009) considered all three species to represent invalid archosauriforms. [5]

Sennikov (2022) interpreted Tsylmosuchus as a member of the Ctenosauriscidae and also suggested that Scythosuchus may have been the same animal as Tsylmosuchus. [1] In contrast, it was recovered as a member of the Proterosuchidae by Ezcurra (2023), who reversed some of his previous reclassifications of the genus. [6]

Paleobiology

Along with small proterosuchids such as Chasmatosuchus , Tsylmosuchus and other large archosauriforms were the top predators in Early Triassic European Russia. Tsylmosuchus was part of what are referred to as the Benthosuchus - Wetlugasaurus fauna (a.k.a. the Ustmylian and Rybinskian gorizonts) and the Parotosuchus fauna (a.k.a. the Yarenskian Gorizont). These faunas extend through the early and late Olenekian stage. They are known from hundreds of sites throughout eastern Europe and preserve a wide array of temnospondyls (primarily trematosaurids), procolophonids, and early archosauriforms. They correspond to a massive river basin, which likely experienced a trend of increasing humidity during the later part of the Olenekian. [3]

Related Research Articles

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

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. 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.

<span class="mw-page-title-main">Proterosuchidae</span> Extinct family of reptiles

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, China, Australia, Brazil and possibly Argentina. The name comes from Greek πρότερο- ("first") and σοῦχος ("crocodile").

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

Teleocrater is a genus of avemetatarsalian archosaur from the Middle Triassic Manda Formation of Tanzania. The name was coined by English paleontologist Alan Charig in his 1956 doctoral dissertation, but was only formally published in 2017 by Sterling Nesbitt and colleagues. The genus contains the type and only species T. rhadinus. Uncertainty over the affinities of Teleocrater have persisted since Charig's initial publication; they were not resolved until Nesbitt et al. performed a phylogenetic analysis. They found that Teleocrater is most closely related to the similarly enigmatic Yarasuchus, Dongusuchus, and Spondylosoma in a group that was named the Aphanosauria. Aphanosauria was found to be the sister group of the Ornithodira, the group containing dinosaurs and pterosaurs.

<i>Proterosuchus</i> Extinct genus of reptiles from the Early Triassic of South Africa

Proterosuchus is an extinct genus of archosauriform reptiles that lived during the Early Triassic. It contains three valid species: the type species P. fergusi and the referred species P. alexanderi and P. goweri. All three species lived in what is now South Africa. The genus was named in 1903 by the South African paleontologist Robert Broom. The genus Chasmatosaurus is a junior synonym of Proterosuchus.

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

Archosaurus is an extinct genus of carnivorous proterosuchid archosauriform reptile. Its fossils are dated to the latest Permian of Russia and Poland, it is one of the earliest known archosauriforms. The type and only species is Archosaurus rossicus, known from several fragmentary specimens which cumulatively represent parts of the skull and cervical vertebrae. It would have been 3 metres (9.8 ft) long when fully grown.

Yarasuchus is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. The genus was named and described in 2005 from a collection of disarticulated but fairly complete fossil material found from the Middle Triassic Yerrapalli Formation. The material is thought to be from two individuals, possibly three, with one being much more complete and articulated than the other. The type and only species is Y. deccanensis. Yarasuchus was a quadruped roughly 2–2.5 metres (6.6–8.2 ft) long, with an elongated neck and tall spines on its vertebrae. Unlike other quadrupedal Triassic reptiles, the limbs and shoulders of Yarasuchus were slender, and more like those of ornithodirans.

Dongusuchus is an extinct genus of archosaur. Fossils have been found from the Donguz Formation outcropping on the banks of the Donguz River in the Orenburg Oblast of Russia. They are associated with a fossil assemblage called the Eryosuchus Fauna, named after the capitosaurid Eryosuchus, the most common organism found from the assemblage. The locality dates back to the Anisian and early Ladinian stages of the Middle Triassic.

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.

Scythosuchus is an extinct genus of rauisuchid. Remains have been found from Olenekian-age Lower Triassic beds in Russia, hence the name meaning 'Scythian crocodile'. The type and only species is S. basileus, described in 1999. Scythosuchus was between 2 and 3 metres long, and relatively heavily built. It is known from a partial skull, much of the spine, a fragment of the humerus and most of the hind leg and foot. It may have been the same animal as Tsylmosuchus donensis.

Vjushkovisaurus is an extinct genus of Middle Triassic archosauriform. It is known from the Anisian-aged Donguz Gorizont in Sol-Iletsk, Orenburg Oblast, Russia. The genus was named in 1982, with the type species being V. berdjanensis. Material has been collected in the Berdyanka II locality from a fossil assemblage called the Eryosuchus Fauna along the Berdyanka River, specifically in a sand-carbonate concretion in the upper part of the main river channel. Vjushkovisaurus is known only from the holotype PIN 2865/62, a partial postcranial skeleton which consists of 12 presacral vertebrae, left humerus, ribs, a fragment of the coracoid and a fragment of the fibula.

Vytshegdosuchus is an extinct genus of paracrocodylomorph archosaur known from the Early Triassic Yarenskian Gorizont of the Komi Republic of the European section of Russia. It contains a single species, Vytshegdosuchus zheshartensis. Vytshegdosuchus was named by Andreii Sennikov in 1988.

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

Youngosuchus is an extinct genus of archosaur from the Middle Triassic of China. The type species is Y. sinensis. Y. sinensis was first described in 1973 as a new species of the erythrosuchid Vjushkovia. In 1985, it was reassigned as its own genus of rauisuchid. A 1992 study supported the original classification of Youngosuchus sinensis as an erythrosuchid, but more recent studies classify it as a "rauisuchian"-grade loricatan archosaur completely unrelated to Vjushkovia, which is most likely a synonym of Garjainia.

Xilousuchus is an extinct genus of poposauroid from lower Triassic deposits of Fugu County of northeastern Shanxi Province, China. It is known from the holotype, IVPP V 6026, a single well-preserved partial skeleton including the skull. It was found from the Heshanggou Formation of the Ordos Basin, Hazhen commune. It was first named by Xiao-Chun Wu in 1981 and the type species is Xilousuchus sapingensis. Wu (1981) referred Xilousuchus to the Proterosuchia. Gower and Sennikov (1996) found it to be an erythrosuchian based strictly on the braincase. A more detailed re-description of the genus was provided by Nesbitt et al. (2010) and found poposauroid affinities. In his massive revision of archosaurs which included a large cladistic analysis, Sterling J. Nesbitt (2011) found Xilousuchus to be a poposauroid which is most closely related to Arizonasaurus. Xilousuchus is the oldest archosaur to date, although Ctenosauriscus and Vytshegdosuchus might be even older by less than one million year. Since Xilousuchus is a suchian archosaur, its early age suggests that most of the major groups of archosaurs developed by the Early Triassic, soon after the appearance of the first archosaur.

Vonhuenia is an extinct genus of proterosuchid, a basal archosauriform from the Early Triassic of Russia. Fossils have been found in the Vokhminskaya Formation, along the Vetluga River that are Induan in age, making Vonhuenia one of the earliest archosauriforms.

Dongusia is an extinct genus of rauisuchid reptile from the Middle Triassic of Russia. The type species D. colorata was named by German paleontologist Friedrich von Huene in 1940 on the basis of a single vertebra. This bone was found in the Sol-Iletsky District of Orenburg Oblast. Huene thought Dongusia was a primitive archosauriform. In the 1960s, D. colorata was included in the early archosauriform genus Erythrosuchus. In 1970, similarities were noted between the Dongusia vertebra and those of the rauisuchid "Mandasuchus" from Tanzania. The vertebra is now thought to belong to a rauisuchid, but the genus Dongusia is considered a nomen dubium because there are no diagnostic features in the single bone that distinguish it from other rauisuchids.

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.

Bystrowisuchus is an extinct genus of ctenosauriscid pseudosuchian archosaur from the Early Triassic of European Russia. Fossils have been found in the Olenekian-age Lipovskaya Formation in Ilovlinsky District. The type species is Bystrowisuchus flerovi.

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.

Scolotosuchus is an extinct genus of rauisuchid from the Early Triassic of Russia. The only known species, Scolotosuchus basileus, has been discovered at the Donskaya Luka Locality. It differs from all other rauisuchids in the morphology of its spine, which allowed it to both resist great stress and gave it a great range of mobility. Additionally, it may have lacked osteoderms, with its spine instead being supported in a similar manner as in dinosaurs. At 3 m (9.8 ft) it was likely the apex predator of its ecosystem.

References

  1. 1 2 Sennikov AG (2022). "On pseudosuchians Tsylmosuchus donensis and Scythosuchus basileus from the Early Triassic of Eastern Europe". Paleontological Journal. 56 (1): 91–96. doi:10.1134/S0031030121060113. S2CID   248132677.
  2. 1 2 3 Sennikov, A.G. (1990). "New data on the rauisuchids of Eastern Europe". Paleontological Journal. 1990 (3): 3–16.
  3. 1 2 3 4 5 Gower, D.J.; Sennikov, A.G. (2003). "Early archosaurs from Russia". In Benton, M.J.; Shishkin, M.A.; Unwin, D.M. (eds.). The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge University Press. pp. 140–159.
  4. Borsuk−Białynicka, M.; Sennikov, A.G. (2009). "Archosauriform postcranial remains from the Early Triassic karst deposits of southern Poland" (PDF). Palaeontologica Polonica. 65: 283–328.
  5. 1 2 Sterling J. Nesbitt (2009). "The early evolution of archosaurs: Relationships and the origin of major clades". Columbia University (Open Access Dissertation): 1–632.
  6. 1 2 3 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). doi:10.1098/rsos.230387. ISSN   2054-5703. PMC   10598453 . PMID   37885992.
  7. Ezcurra, M.D., 2016. The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ 4:e1778;DOI10.7717/peerj.1778