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''Uktenadactylus'' is a genus of pterodactyloid pterosaurs from the Lower Cretaceous Paw Paw Formation of Texas. In 1994 Yuong Nam-Lee named a new species within the genus ''Coloborhynchus'': ''Coloborhynchus wadleighi'', based on a partial snout found in 1992 in Albian layers in Tarrant County, holotype SMU 73058 (Shuler Museum of Paleontology, Southern Methodist University at Dallas). The specific name honours the collector of the fossil, Chris Wadleigh. The reference of the species to the genus ''Coloborhynchus'' was based on the fact that both ''C. wadleighi'' and the type species of ''Coloborhynchus'', ''Coloborhynchus clavirostris'', share the trait of having three pairs of teeth laterally placed within a broad snout tip. This would distinguish both from the species ''Criorhynchus simus'' and justify a revival of the genus ''Coloborhynchus'' that since an analysis by Reginald Walter Hooley in 1914 had generally been considered identical to the genus ''Criorhynchus'' or the genus the latter had again been sunk into, ''Ornithocheirus''. As a result of the reappearance of the concept European workers referred many species discovered in South-America to ''Coloborhynchus'', a practice rejected by most South-American researchers. In 2009 a study by the Brazilian paleontologists Taissa Rodrigues and Alexander Kellner concluded that ''Coloborhynchus'' comprised only a single species, its type species ''C. clavirostris''. Accordingly, in the same publication they created a new genus for ''C. wadleighi'': ''Uktenadactylus''. The genus name is derived from Uktena, a giant horned snake from the mythology of the Cherokee and Greek ''daktylos'', "finger", a common element in the names of pterosaurs since ''Pterodactylus'', referring to their typical wing finger. The fossil has a length of about fifteen centimetres and consists of the front end of the skull, containing the premaxilla and a small part of the maxilla. On top the base of a crest is present, gradually curving upwards and ending at a height of 7.5 centimetres, having attained at that point a thickness of four millimetres. The snout broadens towards the front. On the left side eight tooth sockets or alveoli are visible, on the right side six. The first pair of teeth was located in the flat tip of the snout, pointing forwards. The alveoli at first increase in size from the tip towards the back, the third pair being the largest with a diameter of 17.6/17.7 millimetres. The fourth pair is much smaller; to the back gradually the tooth sockets again increase in size. Thus a "prey grab" is formed. According to Rodrigues and Kellner the species has two unique traits: the presence of an oval depression above and in between the first pair of teeth and of a ventral medial depression between the second pair of teeth, a circular hollow positioned on the lower edge of the snout tip that Lee had interpreted as a possible pneumatic foramen. Rodrigues and Kellner base the distinction between ''Uktenadactylus'' and ''Coloborhynchus clavirostris'' on several stratigraphical, methodological and phylogenetic considerations. There is a possible age difference of perhaps over thirty million years between the Berriasian-Valanginian British and the younger Albian-Cenomanian American form. Because both taxa are based on very limited remains, that however, even within these limits are clearly distinguishable on the species level, they reject a rash assumption of generic identity. Also the uncertain affinity with the closely related form ''Siroccopteryx'' would make such an assumption problematical. Rodrigues and Kellner identify only one shared derived trait for ''Uktenadactylus'' and ''Coloborhynchus clavirostris'': an extreme enlargement of the second and third pairs of teeth. Differences between the taxa include the more forward position of the crest with ''C. clavirostris'', beginning at the very tip of the snout; a deeper palatal groove and shallow grooves running parallel to the ridge of the front part of the palate; a depression located below the first alveoli and a more lateral position of the second, third and fourth tooth pairs whereas the fifth and sixth pair are to the contrary much closer to the midline of the skull. Both forms share some derived traits with ''Siroccopteryx'': the second and third teeth pairs are larger than the fourth; the tip of the snout is flat causing the "prey grab" to be rectangular in cross-section and a similar thickness of the crest. The authors conclude from this that the three taxa likely formed an, as yet unnamed, clade together within the Anhangueridae. ==See also== * List of pterosaurs 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「Uktenadactylus」の詳細全文を読む スポンサード リンク
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