Chemistry Science
The dinosaurs roamed the earth in the Mesozoic era, until they became extinct 65 million years ago, many millions of years before the first human was born. Most of today's animals did not exist then, with the exception of crocodiles, tortoises and insects. Dinosaur skeletons and fossils allow us to reconstruct what dinosaurs looked like. The largest complete dinosaur skeleton ever found was that of a brachiosaurus, which was 13m tall and 23m long. The dangerous, flesh-eating tyrannosaurus was a frightening 5m tall and 13m long. There were swimming dinosaurs and even flying dinosaurs. Today's birds are descended from the flying dinosaurs.