Saurischia (Saur-is'-chi-a). One of the two orders of archosaurian reptiles commonly treated as dinosaurs, characterized by a triradiate pelvis. It includes bipedal predators (Carnosauria, Coelurosauria), quadrupedal long-necked herbivores (Sauropods), and presumptive ancestors of the latter (Prosauropoda). Range, Middle Triassic to Upper Cretaceous. Cf: Ornithischia.