|
''Trachodon'' (meaning "rough tooth") is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S.A.〔Leidy, J. (1856). "Notice of remains of extinct reptiles and fishes, discovered by Dr. F. V. Hayden in the Bad Lands of the Judith River, Nebraska Territories." ''Proceedings of the Academy of Natural Science Philadelphia'', 8(March 25): 72-73.〕 It is a historically important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaur paleontologists.〔Creisler, B.S. (2007). Deciphering duckbills. in: K. Carpenter (ed.), ''Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs''. Indiana University Press: Bloomington and Indianapolis, 185-210. ISBN 0-253-34817-X〕 Despite being used for decades as the iconic duckbill dinosaur per antonomasia the material it is based on is composed of teeth from both duckbills and ceratopsids (their teeth have a distinctive double root〔Hatcher, J.B., Marsh, O.C. and Lull, R.S. (1907). ''The Ceratopsia''. Government Printing Office, Washington, D.C., 300 pp. ISBN 0-405-12713-8〕), and its describer, Joseph Leidy, came to recognize the difference and suggested limiting the genus to what would now be seen as ceratopsid teeth.〔 Restricted to the duckbill teeth, it may have been a lambeosaurine.〔Sternberg, C.M. (1936). The systematic position of ''Trachodon''. ''Journal of Paleontology'' 10(7):652-655.〕 ==History and classification== In 1856, Joseph Leidy received fragmentary remains from the Judith River Formation, collected by Ferdinand Vandeveer Hayden. From these bones, he provided the first names for North American dinosaurs: ''Deinodon'', ''Palaeoscincus'', ''Trachodon'', and ''Troodon'' (then spelled ''Troödon''), the latter being the only name still in use.〔 The type species of ''Trachodon'' is ''T. mirabilis''. The generic name is derived from Greek τραχυς, ''trakhys'', "rough", and όδον, ''odon'', "tooth", referring to the granulate inner surface of one of the teeth. The specific name means "marvelous" in Latin. ''Trachodon'' was based on ANSP 9260, seven unassociated teeth, one of which had double roots. With better remains from ''Hadrosaurus'', he began to reconsider his taxonomy, and suggested, at least informally, that ''Trachodon'' should refer to the double-rooted tooth, and the other teeth should be referred to ''Hadrosaurus''.〔Leidy, J. (1868). Remarks on a jaw fragment of ''Megalosaurus''. ''Proceedings of the Academy of Natural Science Philadelphia'' 20:197-200.〕 In the Bone Wars that followed, and their wake, the taxonomy of ''Trachodon'' and its relatives became increasingly confusing,〔 with one author going so far as to sink all known hadrosaur species into ''Trachodon'' except for ''Claosaurus agilis'',〔Hatcher, J.B. (1902). The genus and species of the Trachodontidae (Hadrosauridae, Claosauridae) Marsh. ''Annals of the Carnegie Museum'' 14(1):377-386.〕 but as new material was described from the Rocky Mountain region, Alberta, and Saskatchewan, later authors began progressively restricting the reach of this genus.〔〔Gilmore, C.W. (1915). On the genus ''Trachodon''. ''Science'' 41:658-660.〕 By 1942, and the publication of the influential Lull-Wright monograph on duckbills, its holotype was regarded as "typical of all the genera of hadrosaurian dinosaur", except for the roughened margin that gave it its name, and that they regarded as due to the tooth having not been used (p. 149).〔Lull, R.S., and Wright, N.E. (1942). Hadrosaurian Dinosaurs of North America. ''Geological Society of America Special Paper 40'':1-242.〕 The name is no longer in use, except in historical discussions, and is considered a ''nomen dubium''.〔Coombs, Jr., W.P. (1988). The status of the dinosaurian genus ''Diclonius'' and the taxonomic utility of hadrosaurian teeth. ''Journal of Paleontology'' 62:812-818.〕〔Weishampel, D.B., and Horner, J.R. (1990). Hadrosauridae. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). ''The Dinosauria.'' University of California Press:Berkeley, 534-561. ISBN 0-520-24209-2〕〔Horner, J.R., Weishampel, D.B., and Forster, C.A. (2004). Hadrosauridae. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). ''The Dinosauria (second edition)''. University of California Press:Berkeley, 438-463. ISBN 0-520-06727-4〕 In 1936, paleontologist Charles Sternberg compared the holotype teeth of ''Trachodon mirabilis'' to those of more completely known hadrosaurids and noted that they were most similar to those of lambeosaurines.〔 It has been reported that paleontologist John R. Horner also found that ''Trachodon'' teeth compare well with the teeth of lambeosaurines, specifically ''Corythosaurus'', though they also share similarities with the genus ''Prosaurolophus''.〔Olshevsky, G. (1997), ("Re: Ye Olde Duckbill Dinosaur" ), discussion group, The Dinosaur Mailing List, 8 August 1997. Accessed 6 April 2013.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Trachodon」の詳細全文を読む スポンサード リンク
|