Hips

• All dinosaurs are classified in one of two large groups, according to the design and shape of their hip bones.

• One of the two large groups of dinosaurs is the Saurischia, meaning "reptile-hipped."

• In a saurischian dinosaur, the lower front pair of rod-shaped bones in the pelvis project down and forward.

• All meat-eating dinosaurs belonged to the Saurischia.

• The biggest dinosaurs, the plant-eating sauropods, belonged to the Saurischia.

• The second of the two groups of dinosaurs
is the Ornithischia, meaning "bird-hipped."

• In an ornithischian dinosaur, the lower front pair of rod-shaped bones in the pelvis, called the pubis bones, project down and backward, lying parallel with another pair, the ischium bones.

• All dinosaurs in the group Ornithischia, from small Heterodontosaurus to huge Triceratops, were plant-eaters.

• In addition to hips, there are other differences between the Saurischia and Ornithischia, such as an "extra" bone called the predentary at the front tip of the lower jaw in ornithischians.

STAR FACT
One way experts assign a dinosaur to a main group is by the structure of its hip bones.

By: Parker, Steve, Dinosaurs