Parareptilia

Parareptilia ("near-reptiles") is an extinct subclass of basal sauropsids ("reptiles"). Traditionally considered the sister taxon to Eureptilia (the group that likely contains all living reptiles and birds), its validity as a monophyletic clade has been disputed by modern cladistic analyses.

"Parareptiles" first arose near the end of the Carboniferous period and achieved their highest diversity during the Permian period. Several ecological innovations were first accomplished by "parareptiles" among reptiles. These include the first reptiles to return to marine ecosystems (mesosaurs), the first bipedal reptiles (bolosaurids such as Eudibamus), the first reptiles with advanced hearing systems (nycteroleterids and others), and the first large herbivorous reptiles, the pareiasaurs, the largest of which reached the sized of oxen. The only "parareptiles" to survive into the Triassic period were the procolophonoids, a group of small lizard-like generalists, omnivores, and herbivores. The largest family of procolophonoids, the procolophonids, rediversified in the Triassic, but subsequently declined and became extinct by the end of the period.