''Benthosuchus'' (meaning "deep water crocodile") is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

temnospondyl Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carbo ...

amphibian from 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 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...

. It was primarily aquatic, living in rivers and lakes. Multiple species are known, with the largest reaching about 2.5 meters in length. Russian paleontologist

Ivan Yefremov Ivan Antonovich (real patronymic Antipovich) Yefremov ( ru , Ива́н Анто́нович (Анти́пович) Ефре́мов; April 23, 1908 – October 5, 1972; last name sometimes transliterated as Efremov) was a Soviet paleonto ...

fremovcalled the genus ''Benthosaurus'' "deep water lizard" (from Ancient Greek βένθος (''benthos'') "depth, deep water") in his original 1929 description, "in view of its clearly indicated adaptation to life in deep water" shown by "the position of the orbits and the flatness of the skull." The type species ''B. sushkini'' honored his late teacher

Petr Sushkin Petr Petrovich Sushkin (russian: Петр Петрович Сушкин; 27 January 1868 – 17 September 1928) was a Russian ornithologist who specialised on comparative anatomy, and evolution of birds, particularly of the birds of prey. Sushkin ...

. The generic name was preoccupied by ''Benthosaurus'' Goode & Bean, 1886, a fish, and he renamed the genus ''Benthosuchus'' ("deep water crocodile") in 1937.Efremov, I. A. (1929). ''Benthosaurus sushkini'', ein neuer Labyrinthodont der permotriassischen Ablagerungen der Sharschenga Flusses. ''Bulletin of the Academy of Sciences of the USSR'' 8:747-770. nglish translation: https://paleoglot.org/files/Efremov%201929b.pdf/ref>Efremov, I.A. (1937). On the Stratification of Continental Permian and Triassic the Soviet Union Based on the Terrestrial Vertebrate Fauna. ''Doklady Akademii Nauk SSSR. Nov. Ser. 16(2)'': 125–132. ''Benthosuchus'' has traditionally been considered a member of the temnospondyl superfamily

Trematosauroidea Trematosauroidea are an important group of Triassic temnospondyl amphibians. They flourished briefly during the Early Triassic, occurring worldwide before declining at the start of the Middle Triassic, although the group continued until the Late ...

, and the family Benthosuchidae was established in 1940 to include ''Benthosuchus'' and the related trematosauroid '' Thoosuchus''. Some recent

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

studies have removed ''Benthosuchus'' from Trematosauroidea entirely, placing it as a closer relative of Mastodonsauroidea, another group of Triassic temnospondyls. Other studies retain ''Benthosuchus'' within Trematosauroidea, but since ''Benthosuchus'' and ''Thoosuchus'' have successively basal positions on these trees they form a paraphyletic grouping, not a valid clade. In either case, Benthosuchidae is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

family containing only ''Benthosuchus''.

Description

''Benthosuchus''

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

is about 0.75 m long (it is comparatively short in young individuals but lengthens with age), and the overall body length is about 2.5 m. It existed in widely overflowing rivers of the East Russian Depression.

Phylogeny

''Benthosuchus'' is traditionally considered a close relative of a group of temnospondyls called capitosaurids. In particular, it bears a close resemblance to the capitosaurid '' Wetlugasaurus''. Many of the early large-scale phylogenetic analyses of temnospondyls place ''Benthosuchus'' within a clade called

Capitosauria Capitosauria is an extinct group of large temnospondyl amphibians with simplified stereospondyl vertebrae. Mainly living as piscivores in lakes and rivers, the Capitosauria and its sister taxon Trematosauria were the only major labyrinthodonts ...

. However, more recent analyses such as that of Fortuny ''et al.'' (2011) recover ''Benthosuchus'' within another clade called

Trematosauria Trematosauria is one of two major groups of temnospondyl amphibians that survived the Permian-Triassic extinction event, the other (according to Yates and Warren 2000) being the Capitosauria. The trematosaurs were a diverse and important group ...

. Occasionally it is grouped near the trematosaurid family

Trematosauridae Trematosauridae are a family of large marine temnospondyl amphibians with many members. They first appeared during the Induan age of the Early Triassic, and existed until around the Carnian stage of the Late Triassic, although by then they wer ...

as a basal member of the group

. Fortuny ''et al.'' found that ''Benthosuchus'' positioned outside Trematosauroidea as a more basal trematosaurian. Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

from Fortuny ''et al.'' (2011) showing the

placement of ''Benthosuchus'':

References

{{Taxonbar, from=Q2395740 Trematosaurs Triassic temnospondyls Extinct animals of Russia Fossil taxa described in 1937 Taxa named by Ivan Yefremov