Dinosaurs and Birds

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Plateosauria indet.
© 2005 Yale Peabody Museum

Ankylosauridae, Dromaeosauridae, Hadrosauridae
© 2005 George E. Phillips, Mississippi Museum of Natural Science

Hypacrosaurus
© 2008 Royal Tyrrell Museum

What are Dinosaurs and Birds? The dinosaurs, which means “terrible lizards,” are a very diverse group of reptiles that have been divided into two groups based on the arrangement of bones in their hips.

The Ornithischia, meaning “bird-hipped” dinosaurs, include, among others, Triceratops, Stegosaurus, and the various “duck-billed” dinosaurs. The Saurischia, or “lizard-hipped” dinosaurs, include the herbivorous sauropods (like brontosaurs and diplodocids) and carnivorous theropods, such as Velociraptor, Dilophosaurus, and Gallimimus of "Jurassic Park" fame.

Birds evolved from theropods— a group of small, predatory dinosaurs, some of which had feathers. Dinosaurs first appeared in the Triassic, and except for the birds, went extinct at the end of the Cretaceous.

First known fossil occurrence: Triassic.

Last known fossil occurrence: Quaternary. This group has living relatives.

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