n. Phylum Chordata, Class Reptilia The common name given to any of certain extinct archosaur reptiles, often very large, that thrived worldwide for some 150 million years and died out at the end of the Mesozoic Era, about 65 million years ago.
extinct archosaurian reptiles which lived from Upper Triassic times to the end of the Cretaceous period. Mostly large or very large animals, dinosaurs included flesh- and plant-eating types. The two main groups of dinosaurs, the Saurischia and Ornithischia, are recognized on the basis of their pelvic structure.
The general name given to describe the land-dwelling reptiles which lived between during the Triassic, Jurassic and Cretaceous period (248 - 65 million years ago).