Triassic: About 250 million to 200 million years ago, serrated reptiles slowly developed into the earliest dinosaurs. By the late Triassic, dinosaurs were already a variety of ethnic groups, known as the "dawn of dinosaurs."
Jurassic: about 65.438+99.6 million years BC (with an error of 600,000 years) to 65.438+45.5 million years BC (with an error of 4 million years).
Cretaceous: It started 6.5438+45 million years ago and ended 66 million years ago.
brief introduction
The sudden disappearance of dinosaurs at the end of Cretaceous 65 million years ago became a mystery in the evolutionary history of life on earth. This mystery has not been solved so far. In the past, all living things on the earth were recorded in fossils.
Many dinosaur fossils have been found in Mesozoic strata. A large number of bones or various shapes can be seen in it. However, in the subsequent Cenozoic strata, there were no fossils of non-bird dinosaurs at all, thus inferring that non-bird dinosaurs died out together in Mesozoic, and now only birds are left. Most scientists agree that "birds belong to dinosaurs".