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Anapsida

(Subclass)

Overview

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An anapsid is an whose skull does not have openings near the temples.1]

While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a coherent 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 which first appeared in the late Carboniferous, the various Permian reptiles which had anapsid skulls, and the Testudines (turtles, tortoises, and terrapins). Many modern paleontologists believe the Testudines are descended from diapsid reptiles which lost their temporal fenestrae, although that view is not generally accepted yet (see Parareptilia for details and references).

Anapsid skull of Caretta caretta (Loggerhead sea turtle) -- a Testudine

The only living reptiles with anapsid skulls are the Testudines. The earliest fossil testudines are from the Triassic, but they were already too like modern turtles to be near the start of their lineage - in particular they already had limb joints within the rib cage. The main article about Testudines covers the debate about their ancestry.

Most of the other reptiles with anapsid skulls, including the millerettids, nyctiphrurets, and pareiasaurs, became extinct in the late Permian period by the Permian-Triassic extinction event. But the procolophonids managed to survive into the Triassic.

Photos

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Taxonomy

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The Subclass Anapsida is a member of the Class Sauropsida. Here is the complete "parentage" of Anapsida:

The Subclass Anapsida is further organized into finer groupings including:

Orders

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Captorhinida

[more]

Cotylosauria

[more]

Mesosauria

[more]

Testudines

, Tortoises, and Terrapins are ectothermic reptiles, most of whose body is shielded by a special bony or cartilagenous shell developed from their ribs. They belong to an anapsid lineage, as can be seen from their solid skullcap. About 300 species are alive today; some are highly endangered. [more]

At least 1,083 species and subspecies belong to the Order Testudines.

More info about the Order Testudines may be found here.

References

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  1. ^ Pough, F. H. et al. (2002) Vertebrate Life, 6th Ed. Prentice Hall Inc., Upper Saddle River, NJ. ISBN 0130412481

Sources

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Last Revised: November 18, 2008