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Dongusuchus
''Dongusuchus'' (meaning ''Donguz River crocodile'' in Greek, for the area where the type specimen was found〔Sennikov, A. G. (1988) Novyye rauizukhidy iz triasa yevropeyskoy chasti SSSR. ''Paleontol. Zhurn.'' 1990 (2): 124-128 Moscow.〕) is an extinct genus of archosauriform. Fossils have been found from the Donguz Formation outcropping on the banks of the Donguz River in the Orenburg Oblast of Russia. They are associated with a fossil assemblage called the ''Eryosuchus'' Fauna, named after the capitosaurid ''Eryosuchus'', the most common organism found from the assemblage. The locality dates back to the Anisian and early Ladinian stages of the Middle Triassic.〔Gower, D. J. and Sennikov, A. G. (2000). Early archosaurs from Russia. In M. J. Benton, E. N. Kurochkin, M. A. Shishkin, D. M. Unwin (eds.), ''The Age of Dinosaurs in Russia and Mongolia''. Cambridge University Press, Cambridge. pp. 140-159〕
Sennikov (1988) and Gower and Sennikov (2000) suggested that ''Dongusuchus'' was a gracile rausuchian with a long, sigmoidally curved neck, unlike the more typical robust short-necked rauisuchians that appear later in the Triassic.〔〔 More recently, Nesbitt (2009) argued that ''Dongusuchus'' represent most probably a non-archosaurian archosauriform. According to Nesbitt (2009) the poorly defined crista tibiofibularis and the absence of a distinct anteromedial tuber of the proximal portion in ''Dongusuchus'' suggest that it is not a member of Archosauria. Although Gower and Sennikov (2000) suggested that the distinct sigmoidal shape of ''Dongusuchus'' femur is unique, a similar shape is present in the femora of some phytosaurs. A paratype tibia was also found to be more closely related to ''Euparkeria'' and phytosaurs, on the basis of its convex and rounded distal surface. Additionally, the proximal surface of the tibia lacks a trait present in nearly all pseudosuchians, a depression on its lateral condyle. Nesbitt assigned ''Dongusuchus'' to Archosauriformes on the basis of the following traits: its femur has a low fourth trochanter, and the distal condyles do not expand markedly beyond the shaft. These traits suggest that ''Dongusuchus'' was an archosauriform more derived than ''Erythrosuchus''.
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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