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anapsid
An anapsid is an amniote whose skull does not have openings near the temples.〔Pough, F. H. et al. (2002) ''Vertebrate Life'', 6th Ed. Prentice Hall Inc., Upper Saddle River, NJ. ISBN 0-13-041248-1〕 Traditionally, the Anapsida are the most primitive subclass of reptiles, the ancestral stock from which Synapsida and Diapsida evolved, making anapsids paraphyletic. It is however doubtful whether all anapsids lack temporal fenestra as a primitive trait, or whether all the groups traditionally seen as anapsids truly lacked fenestra.
==Anapsids and the turtles==
While "anapsid reptiles" or "anapsida" were traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related. Scientists still debate the exact relationship between the basal (original) reptiles that first appeared in the late Carboniferous, the various Permian reptiles that had anapsid skulls, and the Testudines (turtles, tortoises, and terrapins). However, it was later suggested that the anapsid-like turtle skull may be due to reversion rather than to anapsid descent. The majority of modern paleontologists believe that the Testudines are descended from diapsid reptiles that lost their temporal fenestrae. More recent morphological phylogenetic studies with this in mind placed turtles firmly within diapsids, some place turtles as a sister group to extant archosaurs〔.〕 or, more commonly within Lepidosauromorpha.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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