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Leptoceratopsidae is an extinct family of neoceratopsian dinosaurs from Asia and North America. They resembled, and were closely related to, other neoceratopsians, such as the families Protoceratopsidae and Ceratopsidae, but they are more primitive and generally smaller. Definitive leptoceratopsids have so far been found exclusively in the Late Cretaceous period (late Santonian - late Maastrichtian stages) of Asia and Western North America,〔 however material referred to leptoceratopsids from the early Campanian of North Carolina and possibly Sweden extends their geographic range into Eastern North America and potentially Europe. A possible leptoceratopsid ulna, named ''Serendipaceratops'', has been found in Victoria, Australia. However, a 2010 study showed that it could not be confidently referred to any ornithischian family, and is considered a ''nomen dubium''.〔Agnolin, F.L., Ezcurra, M.D., Pais, D.F. and Salisbury, S.W. (2010). "A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: Evidence for their Gondwanan affinities." ''Journal of Systematic Palaeontology'', 8(2): 257-300.〕 Leptoceratopsids range in age from ''Gryphoceratops'', of the late Santonian, to ''Leptoceratops'', right at the end of the Cretaceous in the late Maastrichtian. ''Gryphoceratops'' is the first definitive record of Santonian leptoceratopsid. It was named based on a partial left dentary from Alberta, Canada. ''Gryphoceratops'' represents the oldest known leptoceratopsid and probably the smallest adult-sized ceratopsian known from North America.〔 Leptoceratopsids are known from Eastern North America by a partial maxilla dated to the early Campanian of North Carolina, whilst the European material referred to Leptoceratopsidae consists of isolated teeth and vertebrae from the early Campanian of Sweden. The former represents the first known ceratopsian from Eastern North America, and its specialised maxillary anatomy supports the hypothesis that Appalachia was isolated from Western Europe and Laramidia for an extended period during the Late Cretaceous, resulting in an endemic Late Cretaceous fauna.〔 The shared presence of leptoceratopsids in Appalachia and Western Europe has implications for their biogeographic dispersal, suggesting the possibility that leptoceratopsids entered Appalachia through either Western Europe or Laramidia, however it is also possible that the European leptoceratopsids also represented a distinct endemic assemblage, as the Fennoscandian Shield was also an isolated landmass during the Late Cretaceous. == Phylogeny == Leptoceratopsidae was originally named by Franz Nopcsa von Felső-Szilvás in 1923 as a subfamily Leptoceratopsinae, and its type species is ''Leptoceratops gracilis''. Mackovicky, in 2001, defined it as a stem-based taxon and a family consisting of ''Leptoceratops gracilis'' and all species closer to ''Leptoceratops'' than to ''Triceratops horridus''.〔Makovicky, P.J. 2001. A ''Montanoceratops cerorhynchus'' (Dinosauria: Ceratopsia) braincase from the Horseshoe Canyon Formation of Alberta, In: Tanke, D.H. & Carpenter, K. (Eds.). ''Mesozoic Vertebrate Life''. Bloomington: Indiana University Press. Pp. 243-262.〕 The cladogram below follows the topology from a 2012 analysis by Michael J. Ryan, David C. Evans, Philip J. Currie, Caleb M. Brown and Don Brinkman. }} }} }} }} }} |2= }} }} }} }} }} }} }} }} }} }} ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:1900 till:2060 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:50 start:1900 ScaleMinor = unit:year increment:10 start:1900 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR 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「Leptoceratopsidae」の詳細全文を読む スポンサード リンク
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