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© 2004 Patricia Holroyd, UCMP
Pleurocoelus and Acrocanthosaurus
© 1998 Karen Carr
© 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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