Clade of reptiles characterized by a skull that lacks apertures in the temple regions behind the eyes. This was the condition in the earliest reptiles, the Cotylosauria or ‘stem reptiles’. Four groups flourished in the late Palaeozoic: the Captorhinomorpha; the Mesosauria; the Pareiasauridae; and the Procolophonia, which survived into the Triassic. The only living representatives are the turtles (Chelonia).

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