In Hand Museum - The Dinosaurs T he great dinosaurs roamed the Earth during the Mesozoic Era from 225 to 65 million years ago at which point a mass extinction took place leaving the only surviving dinosaurs, birds. This website provides background information on all the major dinosaur groupings, and has specific information on a typical representative of each major grouping.
Dinosaurs belong to a larger group of animals called the archosaurs .
They differ from the other archosaurs in that the joint between the leg and the hip forms a complete hole. The archosaurs, like their relatives the lepidosaurs , are diapsids . Oddly, Saurischian dinosaurs are the ancestors of extant birds, while the Ornithischians are now all extinct . The Saurischia includes all the meat-eating dinosaurs like Tyrannosaurus , as well as all the giant Sauropods like Apatosaurus . A List of Included Dinosaurs Selecting a species below will bring you to the page about that particular animal.