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, formerly called the subfamily Thoosuchinae and placed within Benthosuchidae.[1][2][3] The benthosuchids were originally composed of the majority of basal trematosaurian forms regarded as the ancestors of the trematosaurids.[4][5][6][7][8] Although the genus was first named in 1940, material from one species, E. yakovlevi, was originally tentatively referred to Trematosuchus in 1926.[9]

Thoosuchus
Temporal range: Early Triassic
Life restoration of Thoosuchus yakovlevi
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Amphibia
Order:
Temnospondyli
Infraorder:
Trematosauria
Superfamily:
Trematosauroidea
Family:
Thoosuchidae
Genus:
Thoosuchus

Efremov, 1940
Species
  • T. acutirostris Efremov, 1940 (type)
  • T. yakovlevi (Ryabinin 1926)
  • T. tardus Getmanov, 1989
  • T. tuberculatus Getmanov, 1989

For its family, Thoosuchus was fairly small, reaching a little over 60 cm with a 15 cm skull.[10]

Thoosuchus jakovlevi skull

Thoosuchus superficially resembles the more derived trematosaurids, but can be distinguished from them on the basis of a deep, narrowing otic notch.[11][12] It had widely spaced orbits and a moderately elongated skull roof that was well ornamented with ridges and grooves, especially on the parietals.[13] This ornamentation is also a characteristic of trematosaurids and has been described as representing a "zone of intensive growth".[14][15] The well developed lateral line system of Thoosuchus is indicative of its presumed aquatic lifestyle.

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).[1]


See also

References
  1. Efremov, I. A. (1940). Preliminary description of the new Permian and Triassic Tetrapoda from U.S.S.R. Trudy Paleontologicheskogo Instituta 10:1–140.
  2. Getmanov, S.N. (1982). A labyrinthodont from the Lower Triassic of the Obshchiy Syrt Region. Paleontological Journal 1982:102-106.
  3. 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.
  4. Hartmann-Weinberg, A. and Kuzmin, F. M. (1936). Untertriadische Stegocephalen der UdSSR Lyrocephalus acutirostris nov. sp. Problems of Paleontology 1:63–84.
  5. Shishkin, M. A. (1964). Stereospondyli. In: Orlpv, I. A., ed. Fundamentals of Palaeontology: amphibians, reptiles and birds Moscow: Nauka. pp. 83–122.
  6. Shishkin, M. A. (1980). The Luzocephalidae, a new Triassic labyrinthodont family. Paleontological Journal 1980:88–101.
  7. Getmanov, S. N. (1989). Triassic amphibians of the East European platform (family Benthosuchidae Efremov). Trudy Paleontologicheskogo Instituta 236:1–102.
  8. 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.
  9. Riabinin, A. N. (1926). Trematosuchus (?) yakovlevi nov. sp. from the Lower Triassic deposits in the surroundings of Rybinsk. Izvestiya Geologicheskago Komiteta 45:519–527.
  10. http://www.angellis.net/Web/PDfiles/amphs.pdf
  11. 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.
  12. Damiani, RJ (2001). A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli). Zoological Journal of the Linnean Society 133:379-482.
  13. 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.
  14. 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.
  15. Bystrow, A. P. (1935). Morphologische Untersuchungen der Deckknochen des Schädels der Wirbeltiere. Acta Zoologica 16:65–141.
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