(Science: zoology) A class of air-breathing oviparous vertebrates, usually covered with scales or bony plates. The heart generally has two auricles and one ventricle. The development of the young is the same as that of birds.
It is nearly related in many respects to aves, or birds. The principal existing orders are Testidunata or chelonia (turtles), Crocodilia, Lacertilla (lizards), ophidia (serpents), and rhynchocephala; the chief extinct orders are dinosauria, Theremorpha, mosasauria, pterosauria, plesiosauria, Ichtyosauria.