Dinosaurs were a class of vertebrates, which evolved 230 million years ago. They lived during the Mesozoic era. They diversified into a huge variety of shapes and sizes, from long-necked giants to speedy, agile carnivores like the raptors. They died out 66 million years ago, probably as a result of an asteroid impact. it is widely believed that theropod dinosaurs, mainly raptors, evolved into birds, and so dinosaurs are not in fact extinct but still alive, and survive into the future as well.