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Natronasaurus
''Natronasaurus'' is a genus of stegosaur that lived in the Late Jurassic Morrison Formation of Natrona County, Wyoming, United States. The type species is ''Stegosaurus longispinus''.
==Taxonomy==
It was originally named ''Stegosaurus longispinus'' by Charles Whitney Gilmore on the basis of UW 20503 (originally UW D54), a partial postcranial skeleton consisting of 42 vertebrae, fragmentary sacrum, two ischia, portion of one pubis, right femur, several ribs and four dermal tail spines. Gilmore diagnosed ''S. longispinus'' from other ''Stegosaurus'' species by the presence of very long dermal spikes, distal caudal vertebral centra rounded in anterior/posterior view, vestigial transverse processes on distal caudal vertebrae, and centra with mushroom-shaped dorsal extensions.〔Gilmore, C.W. 1914. Osteology of the armoured Dinosauria in the United States National Museum, with special reference to the genus ''Stegosaurus''. United States National Museum Bulletin 89: 1–143.〕 Due to the presence of very long tail spines, ''S. longispinus'' was treated as valid by subsequent authors.〔O. Kuhn. 1964. Pars 105. Ornithischia (Supplementum I). In F. Westphal (ed.), Fossilium Catalogus. I: Animalia. IJssel Pers, Deventer, The Netherlands 1-80〕〔P. M. Galton. 1990. Stegosauria. The Dinosauria, D. B. Weishampel, P. Dodson, & H. Osmólska (editors), University of California Press, Berkeley 435-455〕〔P. M. Galton and P. Upchurch. 2004. Stegosauria. In D. B. Weishampel, H. Osmolska, and P. Dodson (eds.), The Dinosauria (2nd edition). University of California Press, Berkeley 343-362〕 At one point, ''S. longispinus'' was seen as a North American species of the African ''Kentrosaurus''.〔Olshevsky, G., and Ford, T. L., 1993. The origin and evolution of the stegosaurs: Gakken Mook, Dinosaur Frontline, v. 4, p. 65-103.〕
Unfortunately, the type specimen of this species was damaged when the water pipes of the University of Wyoming's museum burst.〔Southwell, E. & Breithaupt, B. 2007. The tale of the lost Stegosaurus longispinus Tail. 67th Annual Meeting. Society of Vertebrate Paleontology. Journal of Vertebrate Paleontology, 27, 3, 150A.〕 For this reason, the whereabouts of the type specimen were mistakenly considered to be lost,〔S. C. R. Maidment, D. B. Norman, P. M. Barrett and P. Upchurch. 2008. Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). Journal of Systematic Palaeontology 6(4):367-407〕 although a femur catalogued as part of UW 20503 is still extant, suggesting that parts of the type specimen may have survived.〔Foster, J. (2007). Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. 389pp. ISBN 978-0-253-34870-8.〕〔Galton, P. M. 2010. Species of plated dinosaur Stegosaurus (Morrison Formation, Late Jurassic) of western USA: new type species designation needed. Swiss Journal of Geosciences 103, 187-198.〕
Although the validity of ''Stegosaurus longispinus'' was disputed because the long dermal spines were likely to be a product of ontogeny or sexual dimorphism,〔 the amateur freelance paleontologist Roman Ulansky decided that the long tail spines were sufficient to remove ''S. longispinus'' from ''Stegosaurus'' and place it in a new genus, ''Natronasaurus''. Ulansky interprets ''Natronasaurus '' as a close relative of ''Kentrosaurus'' in accordance with the hypothesis of Olshevsky and Ford (1993).〔Ulansky, R. E., 2014. Evolution of the stegosaurs (Dinosauria; Ornithischia). Dinologia, 35 pp. (Russian ). (PDF ) http://dinoweb.narod.ru/Ulansky_2014_Stegosaurs_evolution.pdf.〕
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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