Classification of the Dinosaurs

Updated May 8, 2019 | Infoplease Staff

Dinosaurs (“terrible lizards”) belong to a large group of reptiles called Archosauria (“ruling reptiles”). They are classified into two distinct orders, which are distinguished by their pelvic differences.

Saurischia

All Saurischian (“lizard-hipped”) dinosaurs had modern lizardlike pelvises and clawed feet. Saurischians roamed Earth from the Middle Triassic to the end of the Cretaceous period. They included carnivores and herbivores. Members of the order included Allosaurus (“different lizard”), Apatosaurus (“deceptive lizard”), which was formerly called Brontosaurus, and Tyrannosaurus (“tyrant lizard”). The group is divided into two suborders: Theropoda (“beast footed”) and Sauropodomorpha (“lizard-footed forms”). Velociraptor (“swift robber”) was a theropod.

Ornithischia

All Ornithischian (“bird-hipped”) dinosaurs had pelvises similar to those of modern birds, and hoofed toes. All were herbivores. These dinosaurs lived throughout the world from the Middle Triassic to the end of the Cretaceous period. Members of the order included Iguanodon (“iguana tooth”), Stegosaurus (“plated lizard”), and Triceratops (“three-horned face”). The order is divided into four suborders: Ornithopoda (“bird footed”), Stegosauria (“plated lizards”), Ankylosauria (“armored lizards”), and Certopsia (“horned faces”).