Tsylmosuchus
   HOME

TheInfoList



OR:

''Tsylmosuchus'' is an extinct
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of proterosuchid archosauriform reptile known from Western
Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
. Fossils referred to ''Tsylmosuchus'' occurred over a wide area in sediments corresponding to the
Induan The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.9 Ma and 249.9 Ma (million years ago). The Induan is so ...
and
Olenekian In the geologic timescale, the Olenekian is an age (geology), age in the Early Triassic epoch (geology), epoch; in chronostratigraphy, it is a stage (stratigraphy), stage in the Lower Triassic series (stratigraphy), series. It spans the time betw ...
stages of the
Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...
. Most of these fossils are fragmentary neck vertebrae which were originally reported as sharing similarities with crocodile-line archosaurs (
pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...
ns) 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 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 ...
.


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. The holotype of the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
''T. jakovlevi'' was found near Ust'-Tsylma in the
Komi Republic The Komi Republic (; ), sometimes simply referred to as Komi, is a republics of Russia, republic of Russia situated in the northeast of European Russia. Its capital city, capital is the types of inhabited localities in Russia, city of Syktyvka ...
. This specimen and other referred material (such as ilia) come from the Mezen' and
Pechora Pechora (; ) is a types of inhabited localities in Russia, town in the Komi Republic, Russia, located on the Pechora (river), Pechora River, west of and near the northern Ural Mountains. The area of the town is . Population: History Pechor ...
river basins, which preserve sediments of the Sludkian and Ustmylian gorizonts (early
Olenekian In the geologic timescale, the Olenekian is an age (geology), age in the Early Triassic epoch (geology), epoch; in chronostratigraphy, it is a stage (stratigraphy), stage in the Lower Triassic series (stratigraphy), series. It spans the time betw ...
). Some material once referred to the proterosuchid '' Chasmatosuchus magnus'' has since been referred to this species. ''T. donensis'' comes from the Donskaya Luka site in
Volgograd Oblast Volgograd Oblast ( rus, Волгоградская область, p=vəɫɡɐˈgratskəjə ˈobɫəsʲtʲ) is a federal subjects of Russia, federal subject (an oblast) of Russia, located in the Volga region, lower Volga region of Southern Russia ...
, 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 Obshchy Syrt (, ) is a highland ridge, or plateau ('' syrt''), in the European part of Russia. It starts north of Orenburg as a branch of the Ural Mountains and runs in a southwesterly direction to the east bank of the Volga River. River Shagan, ...
) dating to the Rybinskian Gorizont (
Induan The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.9 Ma and 249.9 Ma (million years ago). The Induan is so ...
), was synonymized with ''Chasmatosuchus rossicus'' by Ezcurra (2016), who also made the ''Tsylmosuchus'' type species a ''nomen dubium''.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 However, in 2023, Ezcurra reversed this decision and placed all three species in ''Tsylmosuchus'' again, and found the genus to be a proterosuchid.


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 ''Vytshegdosuchus'' is an extinct genus of paracrocodylomorph archosaur known from the Early Triassic (latest Olenekian stage) Yarenskian Gorizont of the Komi Republic of the European section of Russia. It contains a single species, ''Vytshegdo ...
''), ''Tsylmosuchus'' has elongated cervical vertebrae. This would have given it a relatively long neck. Nesbitt (2009) suggested that elongated
cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...
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
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
s of each of the three species consist of a single
cervical vertebra In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sauropsid s ...
, 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. Sennikov (2022) interpreted ''Tsylmosuchus'' as a member of the Ctenosauriscidae and also suggested that '' Scythosuchus'' may have been the same animal as ''Tsylmosuchus''. In contrast, it was recovered as a member of the Proterosuchidae by Ezcurra (2023), who reversed some of his previous reclassifications of the genus.


Paleobiology

Along with small proterosuchids such as ''
Chasmatosuchus ''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 t ...
'', ''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 ''Parotosuchus'' is an extinct genus of capitosaurian temnospondyls within the family Mastodonsauridae. Fossils are known from the Early Triassic of Europe, Africa, Australia, and Antarctica. It was about long and likely lived in aquatic envir ...
'' fauna (a.k.a. the Yarenskian Gorizont). These faunas extend through the early and late
Olenekian In the geologic timescale, the Olenekian is an age (geology), age in the Early Triassic epoch (geology), epoch; in chronostratigraphy, it is a stage (stratigraphy), stage in the Lower Triassic series (stratigraphy), series. It spans the time betw ...
stage. They are known from hundreds of sites throughout eastern Europe and preserve a wide array of
temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...
s (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.


References


External links


''Tsylmosuchus''
in the
Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...
{{Taxonbar, from=Q3335923 Proterosuchidae Early Triassic reptiles of Europe Prehistoric reptile genera Fossil taxa described in 1990