Dinosaur divisions

Dinosaurs are divided into two groups based on the shape of their hips: saurischians (lizard-hipped) and ornithischians (bird-hipped). Saurischians had one lower hipbone pointing downward and forward, and the other downward and backward. ornithischians had their two lower hipbones pointing downward and backward.

Period

Millions of years ago

Examples of dinosaurs from each period

Cretaceous

65-145

Jurassic

145-208

Stegosaurus

Triassic

208-245

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