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''Ceratops'' (meaning "horn face") is a dubious genus of herbivorous ceratopsian dinosaur which lived during the Late Cretaceous. Its fossils have been found in Montana. Although poorly known, ''Ceratops'' is important in the history of dinosaurs, since it is the type genus for which both the Ceratopsia and the Ceratopsidae have been named. The material is too poor to be confidently referred to better specimens, and ''Ceratops'' is thus considered a ''nomen dubium''. ==History== The first remains referred to ''Ceratops'' — an occipital condyle and a pair of horn cores — were found by John Bell Hatcher (1861–1904) in the late summer of 1888 near the Cow Creek in Blaine County in the uppermost Judith River Formation of Montana. Hatcher was at the time employed by Professor Othniel Charles Marsh who the same year named the find as the type species ''Ceratops montanus''. The generic name was derived from Greek κέρας, ''keras'', "horn", and ὤψ, ''ops'', "face". The specific name referred to Montana. Marsh originally believed the animal to be similar to ''Stegosaurus'', but with two horns on the back of its head, a body length of twenty-five to thirty feet, horizontal plates on its back and bipedal. According to Marsh it would have "represented a very strange appearance".〔O.C. Marsh, 1888, "A new family of horned Dinosauria, from the Cretaceous", ''The American Journal of Science, series 3'' 36: 477-478〕 In his illustration of the horn pair, purportedly showing them from behind, Marsh had switched their position and rotated their outside to the rear to make them point inwards.〔J.B. Hatcher, O.C. Marsh, and R.S. Lull, 1907, ''The Ceratopsia''. Monographs of the United States Geological Survey 49 pp 198〕 The holotype, USNM 2411, was found in a layer dating from the Campanian. It consists, apart from the occipital condyle, of two supraorbital horn cores of about twenty-two centimetres length.〔 The right horn is attached to a part of the prefrontal. Marsh later referred two squamosals to the species, specimens USNM 4802 and USNM 2415. These however are more likely centrosaurine; they have also been referred to ''Avaceratops''.〔Penkalski, P.G., 1993, "The morphology of ''Avaceratops lammersi'', a primitive ceratopsid from the Campanian of Montana", ''Journal of Vertebrate Paleontology'' 13(3, supplement): 52A〕 In 1906 Richard Swann Lull noted that the name ''Ceratops'' had been preoccupied by a bird, ''Ceratops'' Rafinesque 1815, but also that this had been an undescribed ''nomen nudum'', causing the name to have been still available in 1888. He nevertheless provisionally proposed a replacement name: ''Proceratops''.〔R.S. Lull, 1906, "A new name for the dinosaurian genus ''Ceratops''", ''The American Journal of Science, series 4'' 21: 144〕 This is thus a junior synonym of ''Ceratops''. Already in the early twentieth century new finds made it increasingly difficult to distinguish the limited remains of ''Ceratops'' from several other related forms. Today, ''Ceratops'' is considered a ''nomen dubium''.〔P. Dodson and P. J. Currie, 1990, "Neoceratopsia". In: D.B. Weishampel, H. Osmolska, and P. Dodson (eds.), ''The Dinosauria''. First Edition. University of California Press, Berkeley pp 593-618〕 However, from time to time claims are made about discoveries that, also taking into regard their provenance, might have a provable connection with the ''Ceratops'' holotype. In 1995, David Trexler and F.G. Sweeney noted that complete material from a bonebed that had been found in Montana could enable ''Ceratops'' to be reexamined. The site, known as the Mansfield Bonebed, belongs to the same stratigraphic level as the one the yielded the original ''Ceratops'' remains. It had initially been interpreted as containing ''Styracosaurus'', but what earlier authors considered the frill spikes of ''Styracosaurus'' turned out to be chasmosaurine orbital horns. Trexler and Sweeney pointed out that these horns closely resembled those of ''Ceratops'', and could allow the genus to be rescued as a valid name.〔Trexler, D. and Sweeney, F.G. (1995). "Preliminary work on a recently discovered ceratopsian (Dinosauria: Ceratopsidae) bonebed from the Judith River Formation of Montana suggests the remains are of ''Ceratops montanus'' Marsh." ''Journal of Vertebrate Paleontology'', 15(3, Suppl.): 57A.〕 The ceratopsids in the bonebed were later referred to the genus ''Albertaceratops'', and later re-classified in their own genus, ''Medusaceratops''.〔Ryan, Michael J.; Russell, Anthony P., and Hartman, Scott. (2010). "A New Chasmosaurine Ceratopsid from the Judith River Formation, Montana", In: Michael J. Ryan, Brenda J. Chinnery-Allgeier, and David A. Eberth (eds), ''New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium'', Indiana University Press, 656 pp. ISBN 0-253-35358-0.〕 In 1999, Paul Penkalski and Peter Dodson concluded that ''Ceratops'', despite being is a ''nomen dubium'' because the material is too meager, appeared closely related to ''Avaceratops'' which even may be a juvenile ''Ceratops''; there is not enough material to prove it. In 2005, remarkably well preserved cranial and postcranial elements of a Judithian ceratopsian were discovered in Fergus County, Montana. Nicknamed "Judith", preliminary examination suggested a close affinity with ''C. montanus''. The locality has been determined to be on or in close proximity to the stratigraphic layer of ''C. montanus'', and not too many miles away. The fossils have since been meticulously prepared, studied and evaluated. A team of researchers consisting of Christopher Ott, Peter Larson, Joe Small, Edward Iuliano, Bill Shipp, Linda Shipp, and Kurt Spearing submitted a manuscript paper describing the specimen, with a projected publication date of late 2013.〔"(Judith the Dinosaur )". Accessed 17-AUG-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「Ceratops」の詳細全文を読む スポンサード リンク
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