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Ichthyostegalia is an order of extinct amphibians, representing the earliest landliving vertebrates. The group is thus an evolutionary grade rather than a clade. While the group are recognized on having feet rather than fins, most, if not all, had internal gills in adulthood and lived primarily as shallow water fish and spent minimal time on land. The group evolved from elpistostegalian fish in early or middle Devonian.〔Uppsala University (2010, January 8). Fossil footprints give land vertebrates a much longer history. ScienceDaily. Retrieved January 8, 2010, from http://www.sciencedaily.com /releases/2010/01/100107114420.htm〕 They continued to thrive as denizens of swampland and tidal channels throughout the period. They gave rise to the Temnospondyli and then disappeared at the transition to the Carboniferous. ==Classification== *Ichthyostegalia * *Acanthostegidae * * *Acanthostega * *Densignathidae * * *Densignathus * *Elginerpetontidae * * *Elginerpeton * * *Obruchevichthys * *Ichthyostegidae * * *Hynerpeton * * *Ichthyostega * *Jakubsonidae * * *Jakubsonia * *Metaxygnathidae * * *Metaxygnathus * *Sinostegidae * * *Sinostega * *Tulerpetontidae * * *Tulerpeton * *Ventastegidae * * *Ventastega * *Ymeridae * * *Ymeria 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「Ichthyostegalia」の詳細全文を読む スポンサード リンク
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