Dinosite header

The earliest dinosaurs and mammals date back to the late Triassic period, about 225 million years ago. Most of the first Triassic dinosaurs were small and quick meat-eaters that walked on their hind legs. By the end of the Triassic period (about 20 million years ago), larger prosauropods (20-foot-long plant-eating dinosaurs) were beginning to appear.

Triassic Period

The Jurassic period began about 200 million years ago and lasted about 55 million years. Many new types of dinosaurs, mammals, and reptiles emerged during the Jurassic, including the plated dinosaurs and the sauropods heavy, long-necked dinosaurs that walked on four legs. There were also large theropods, or meat-eating dinosaurs, roaming the Earth. The first birds (and bird-like dinosaurs) also appeared during the Jurassic period.

Jurassic Period

The Cretaceous period began about 145 million years ago and ended 65 million years ago with the extinction of the dinosaurs. Flowering plants and modern insects appeared. Dinosaurs of all shapes and sizes walked the land, including duckbills, armored, horned, and dome-headed dinosaurs. There were new forms of giant meat-eaters, as well as a deadly new breed of hunter, the "raptor" dinosaur, known for its sharp teeth and curved claw on each hand and foot.

Cretaceous Period