Thoosuchus

{{Short description|Extinct genus of amphibians}} {{Automatic_taxobox | fossil_range = [[Early Triassic]] | image = Thoosuchus.jpg | image_caption = Life restoration of ''Thoosuchus yakovlevi'' | taxon = Thoosuchus | authority = [[Ivan Yefremov|Efremov]], 1940 | subdivision_ranks = Species | subdivision = *''T. abbasovi'' Novikov, 2021 *''T. acutirostris'' Efremov, 1940 ([[type species|type]]) *''T. yakovlevi'' (Ryabinin 1926) *''T. tardus'' Getmanov, 1989 *''T. tuberculatus'' Getmanov, 1989 }}

'''''Thoosuchus''''' (meaning "active crocodile") is an extinct [[genus]] of [[basal (phylogenetics)|basal]] [[Trematosauroidea|trematosauroid]] [[trematosauria]]n [[Temnospondyli|temnospondyl]]. [[Fossil]]s have been found from [[Russia]] and date back to the [[Early Triassic]]. It is the [[type genus]] of the [[Family (taxonomy)|family]] [[Thoosuchidae]], formerly called the [[subfamily]] Thoosuchinae and placed within [[Benthosuchidae]].<ref name=Efremov1940> Efremov, I. A. (1940). Preliminary description of the new Permian and Triassic Tetrapoda from U.S.S.R. ''Trudy Paleontologicheskogo Instituta'' '''10''':1–140.</ref><ref>Getmanov, S.N. (1982). A labyrinthodont from the Lower Triassic of the Obshchiy Syrt Region. ''Paleontological Journal'' '''1982''':102-106.</ref><ref>Damiani, R. J. and Yates, A. M. (2003). The Triassic Amphibian ''Thoosuchus yakovlevi'' and the Relationships of the Trematosauroidea (Temnospondyli: Stereospondyli). ''Records of the Australian Museum'' '''55''':331–342.</ref> The benthosuchids were originally composed of the majority of basal trematosaurian forms regarded as the ancestors of the trematosaurids.<ref>Hartmann-Weinberg, A. and Kuzmin, F. M. (1936). Untertriadische Stegocephalen der UdSSR ''Lyrocephalus acutirostris'' nov. sp. ''Problems of Paleontology'' '''1''':63–84.</ref><ref>Shishkin, M. A. (1964). Stereospondyli. ''In:'' Orlpv, I. A., ed. ''Fundamentals of Palaeontology: amphibians, reptiles and birds'' Moscow: Nauka. pp. 83–122.</ref><ref>Shishkin, M. A. (1980). The Luzocephalidae, a new Triassic labyrinthodont family. ''Paleontological Journal'' '''1980''':88–101.</ref><ref>Getmanov, S. N. (1989). Triassic amphibians of the East European platform (family Benthosuchidae Efremov). ''Trudy Paleontologicheskogo Instituta'' '''236''':1–102.</ref><ref>Shishkin, M. A. and Welman, J. (1994). A new find of ''Trematosuchus'' (Amphibia, Temnospondyli) from the Cynognathus Zone of South Africa. ''Palaeontologia africana'' '''31''':39–49.</ref>

== Discovery and naming == Although the genus was first named in 1940, material from one species, ''E. yakovlevi'', was originally tentatively referred to ''[[Trematosuchus]]'' in 1926.<ref>Riabinin, A. N. (1926). ''Trematosuchus (?) yakovlevi'' nov. sp. from the Lower Triassic deposits in the surroundings of Rybinsk. ''Izvestiya Geologicheskago Komiteta'' '''45''':519–527.</ref> Russian paleontologist [[Ivan Yefremov]] [Efremov] named it ''Thoosuchus'' "active crocodile" (from Ancient Greek θοός (thoos) "nimble, active" and σοῦχος (soukhos) "crocodile") in 1940, "in view of its obviously more active mode of life in water than the mode of life of ''[[Benthosuchus]]''" (page 13).<ref name=Efremov1940/>

== Description == [[File:Thoosuchus jakovlevi.JPG|thumb|left|''Thoosuchus jakovlevi'' skull]] For its family, ''Thoosuchus'' was fairly small, reaching a little over 60 cm with a 15 cm [[skull]].<ref>{{Cite web | url=http://www.angellis.net/Web/PDfiles/amphs.pdf | title=List of Genus/Species | website=www.angellis.net}}</ref>

''Thoosuchus'' superficially resembles the more derived [[Trematosauridae|trematosaurids]], but can be distinguished from them on the basis of a deep, narrowing [[otic notch]].<ref>Yates, A. M. and Warren, A. A. (2000). The phylogeny of the 'higher' temnospondyls (Vertebrata: Choanata) and its implications for the monophyly and origins of the Stereospondyli. ''Zoological Journal of the Linnean Society'' '''128''':77-121.</ref><ref>Damiani, RJ (2001). A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli). ''Zoological Journal of the Linnean Society'' '''133''':379-482.</ref> It had widely spaced orbits and a moderately elongated skull roof that was well ornamented with ridges and grooves, especially on the [[Parietal bone|parietals]].<ref>Shishkin, M. A., Novikov, I. V. and Gubin, Y. M. (2000). Permian and Triassic temnospondyls from Russia. ''In:'' Benton, M. J., Shishkin, M. A., Unwin, D. M. and Kurochkin, E. N. (eds.), ''The Age of Dinosaurs in Russia and Mongolia''. Cambridge University Press, pp. 35-59.</ref> This ornamentation is also a characteristic of trematosaurids and has been described as representing a "zone of intensive growth".<ref>Säve-Söderbergh, G. (1937). On the dermal skulls of ''Lyrocephalus'', ''Aphaneramma'', and ''Benthosaurus'', labyrinthodonts from the Triassic of Spitsbergen and N. Russia. ''Bulletin of the Geological Institution of the University of Uppsala'' '''27''':189–208.</ref><ref>Bystrow, A. P. (1935). Morphologische Untersuchungen der Deckknochen des Schädels der Wirbeltiere. ''Acta Zoologica'' '''16''':65–141.</ref> The well developed lateral line system of ''Thoosuchus'' is indicative of its presumed aquatic lifestyle.

== Phylogeny == ''Thoosuchus'' in a [[cladogram]] after Novikov (2018) with only Early Triassic Eastern Europe taxa included:<ref name=Novikov2018>{{cite book|author=Novikov A.V.|year=2018|url=https://new.ras.ru/upload/iblock/7de/j85vtubof3mlf81izrqq9u9oh9eb5lrh.pdf|title=Early Triassic amphibians of Eastern Europe: evolution of dominant groups and peculiarities of changing communities|publisher=Moscow: RAS|page=138|lang=ru|isbn=978-5-906906-71-7|access-date=February 8, 2024|archive-date=December 8, 2023|archive-url=https://web.archive.org/web/20231208092959/https://new.ras.ru/upload/iblock/7de/j85vtubof3mlf81izrqq9u9oh9eb5lrh.pdf|url-status=dead}}</ref>

{{cladex| style=font-size:100%;line-height:100% |label1=[[Temnospondyli]] |1= {{Barlabel|size=24|at=2|label=[[Lydekkerinidae]]|colour=green|style=font-size:100% |cladogram= {{cladex |1=''[[Luzocephalus]]'' |barbegin1 = green |barend1 = green |2={{cladex |label1=[[Capitosauridae]] |1={{cladex |1={{cladex |1=''[[Samarabatrachus]]'' |2={{cladex |1=''[[Poryolosuchus]]'' |2=''[[Parotosuchus]]'' }} }} |2={{cladex |1=''[[Selenocara]]'' |2={{cladex |1=''[[Wetlugasaurus]]'' |2=''[[Vladlenosaurus]]'' }} }} }} |2= {{Barlabel|size=13|at=1|label=[[Qantasidae]]|colour=violet|style=font-size:100% |cladogram= {{clade |1=''[[Qantas (genus)|Qantas]]'' |barbegin1 = violet |barend1 = violet |2={{clade |label1=[[Trematosauridae]] |1={{clade |1=''[[Prothoosuchus]]'' |2={{clade |1='''''Thoosuchus''''' |2={{clade |1=''[[Trematotegmen]]'' |2={{clade |1=''[[Angusaurus]]'' |2={{clade |1=''[[Inflectosaurus]]'' |2=''[[Trematosaurus]]'' }} }} }} }} }} |2= {{Barlabel|size=4|at=1|label=[[Benthosuchidae]]|colour=blue|style=font-size:100% |cladogram= {{cladex |1=''[[Syrtosuchus]]'' |barbegin1 = blue |2={{cladex |1=''[[Benthosuchus]]'' |barend1 = blue |2={{cladex |label1=[[Yarengiidae]] |1={{cladex |1=''[[Vyborosaurus]]'' |2=''[[Yarengia]]'' }} }} }} }} }} }} }} }} }} }} }} }}

==See also== {{Portal|Paleontology}} * [[Prehistoric amphibian]] * [[List of prehistoric amphibians]]

==References== {{Reflist}}

==External links== *[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=37092 Thoosuchus] in the [[Paleobiology Database]]

[[Category:Extinct animals of Russia]] [[Category:Triassic temnospondyls]] [[Category:Taxa named by Ivan Yefremov]] [[Category:Fossil taxa described in 1940]] [[Category:Prehistoric amphibian genera]] [[Category:Early Triassic life]]