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Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defined by Michel Laurin (2001) and Vallin and Laurin (2004) as the largest clade that includes ''Homo sapiens'', but not ''Ascaphus truei''. The informal variant of the name, "reptiliomorphs", is also occasionally used to refer to stem-amniotes, i.e. a grade of reptile-like labyrinthodont tetrapods that are more closely related to amniotes than they are to lissamphibians, but are not amniotes themselves; the name is used in this meaning e.g. by Ruta, Coates and Quicke (2003). An alternative name, "Anthracosauria", is also commonly used for the group, but is confusingly also used for the more primitive grade of reptiliomorphs by Benton.〔Benton, M. J. (2000), ''Vertebrate Paleontology'', 2nd Ed. Blackwell Science Ltd 3rd ed. 2004 – see also (taxonomic hierarchy of the vertebrates ), according to Benton 2004〕 As the exact phylogenetic position of Lissamphibia within Tetrapoda remains uncertain, it also remains controversial which fossil tetrapods are more closely related to amniotes than to lissamphibians, and thus, which ones of them were reptiliomorphs in any meaning of the word. ==Changing definitions== The name Reptiliomorpha was coined by Professor Gunnar Säve-Söderbergh in 1934 to designate amniotes and various types of late Paleozoic tetrapods that were more closely related to amniotes than to living amphibians. In his view, the amphibians had evolved from fish twice, with one group composed of the ancestors of modern salamanders and the other, which Säve-Söderbergh referred to as Eutetrapoda, consisting of anurans (frogs), amniotes and their ancestors, with the origin of caecilians being uncertain. Säve-Söderbergh's Eutetrapoda consisted of two sister-groups: Batrachomorpha, containing anurans and their ancestors, and Reptiliomorpha, containing anthracosaurs and amniotes. Säve-Söderbergh subsequently added Seymouriamorpha to his Reptiliomorpha as well. Alfred Sherwood Romer rejected Säve-Söderbergh's theory of a biphyletic amphibia and used the name Anthracosauria to describe the labyrinthodont lineage from which amniotes evolved. In 1970, the German paleontologist Alec Panchen took up Säve-Söderberghs name for this group as having priority,〔Panchen, A. L. (1970). ''Handbuch der Paläoherpetologie - Encyclopedia of Paleoherpetology Part 5a - Batrachosauria (Anthracosauria),'' Gustav Fischer Verlag - Stuttgart & Portland, 83 pp., ISBN 3-89937-021-X.〕 but Romer's terminology is still in use, e.g. by Carroll (1988 and 2002) and by Hildebrand & Goslow (2001).〔Carroll, R. L., (1988): ''Vertebrate paleontology and evolution''. W. H. Freeman and company, New York.〕 Some writers preferring phylogenetic nomenclature use Anthracosauria.〔Gauthier, J., Kluge, A.G., & Rowe, T. (1988): "The early evolution of the Amniota". In ''The phylogeny and classification of the tetrapods, no 1: amphibians, reptiles, birds''. Edited by M.J. Benton. Clarendon Press, Oxford, pp. 103–155.〕 In 1956, Friedrich von Huene included both amphibians and anapsid reptiles in the Reptiliomorpha. This included the following orders: Anthracosauria, Seymouriamorpha, Microsauria, Diadectomorpha, Procolophonia, Pareiasauria, Captorhinidia, Testudinata.〔Von Huene, F., (1956), ''Paläontologie und Phylogenie der niederen Tetrapoden'', G. Fischer, Jena.〕 Michael Benton (2000, 2004) made it the sister-clade to Lepospondyli, containing "anthracosaurs" (in the strict sense, i.e. Embolomeri), seymouriamorphs, diadectomorphs and amniotes.〔 However, when considered in a Linnean framework, Reptiliomorpha is given the rank of superorder and includes only reptile-like amphibians, not their amniote descendants.〔''Systema Naturae'' (2000) / Classification (Superorder Reptiliomorpha )〕 Several phylogenetic studies indicate that amniotes and diadectomorphs share a more recent common ancestor with lepospondyls than with seymouriamorphs, ''Gephyrostegus'' and Embolomeri (e.g. Laurin and Reisz, 1997, 1999; Ruta, Coates and Quicke, 2003;〔 Vallin and Laurin, 2004;〔 Ruta and Coates, 2007). Lepospondyls are one of the groups of tetrapods suggested to be ancestors of living amphibians; as such, their potential close relationship to amniotes has important implications for the content of Reptiliomorpha. Assuming that lissamphibians aren't descended from lepospondyls but from a different group of tetrapods, e.g. from temnospondyls,〔〔 it would mean that Lepospondyli belonged to Reptiliomorpha ''sensu'' Laurin (2001), as it would make them more closely related to amniotes than to lissamphibians. On the other hand, if lissamphibians are descended from lepospondyls,〔〔〔 then not only Lepospondyli would have to be excluded from Reptiliomorpha, but seymouriamorphs, ''Gephyrostegus'' and Embolomeri would also have to be excluded from this group, as this would make them more distantly related to amniotes than living amphibians are. In that case, the clade Reptiliomorpha ''sensu'' Laurin would contain, apart from Amniota, only diadectomorphs and possibly also ''Solenodonsaurus''.〔 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「Reptiliomorpha」の詳細全文を読む スポンサード リンク
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