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

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 ...

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 ...

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

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

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 ...

. 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 (Antipovich) Yefremov, sometimes Efremov (; 23 April 1908 – 5 October 1972) was a Soviet paleontologist, science-fiction author and social thinker. He founded taphonomy, the study of fossilization patterns. Biography He ...

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 (; 27 January 1868 – 17 September 1928) was a Russian and Soviet based ornithologist who specialised on comparative anatomy, and evolution of birds, particularly of the birds of prey. Sushkin was born in Tula, Russia, in ...

. 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 ''Thoosuchus'' (meaning "active crocodile") is an extinct genus of basal trematosauroid trematosaurian temnospondyl. Fossils have been found from Russia and date back to the Early Triassic. It is the type genus of the family Thoosuchidae, form ...

''. Some recent

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

studies have removed ''Benthosuchus'' from Trematosauroidea entirely, placing it as a closer relative of

Mastodonsauroidea The Mastodonsauroidea are an extinct superfamily (zoology), superfamily of Temnospondyli, temnospondyl amphibians known from the Triassic. Fossils belonging to this superfamily have been found in North America, Greenland, Europe, Asia, and Austr ...

, 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 Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

grouping, not a valid clade. Benthosuchidae was widely considered to be 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 "unisp ...

family containing only ''Benthosuchus'', until the discovery of the related ''

Kwatisuchus ''Kwatisuchus'' (from the Tupi ''kwa 'tim'' for 'pointy nose' and the Greek ''suchus'' for crocodile) is a genus of benthosuchid temnospondyl amphibian from Early Triassic deposits of Brazil. It is represented by the type species, ''Kwatisuchus ...

'' in 2024.

Description

''Benthosuchus''

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

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 ''Wetlugasaurus'' (meaning "Vetluga River lizard") is an extinct genus of temnospondyl from the Early Triassic (Olenekian) Charkabozh, Kzylsaiskaya, Petropavlovka, Kamennyi Yar and Vetluga Series Formations of northern Russia and Greenland. ...

''. Many of the early large-scale phylogenetic analyses of temnospondyls place ''Benthosuchus'' within a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

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 t ...

. Occasionally it is grouped near the trematosaurid family

Trematosauridae Trematosauridae is a family of large marine temnospondyls with several included genera. Appearance and lifestyle Trematosaurids are one of the most derived families of the Trematosauroidea superfamily in that they are the only family that hav ...

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 language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

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

placement of ''Benthosuchus'': Cladogram after Novikov (2018) with only Early Triassic Eastern Europe taxa included:

References

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