any cold-blooded vertebrate of the class Reptilia including tortoises, turtles, snakes, lizards, alligators, crocodiles, and extinct forms

probably warm-blooded; considered direct ancestor of mammals

intermediate in form between the therapsids and most primitive true mammals

large primitive reptile having a tall spinal sail; of the Permian or late Paleozoic in Europe and North America

heavy-bodied reptile with a dorsal sail or crest; of the late Paleozoic

carnivorous dinosaur of the Permian in North America having a crest or dorsal sail