How did dinosaurs disappear?

When an asteroid hit the earth 66 million years ago, the dinosaur ecosystem was in a fragile period, and the environment changed dramatically because of the asteroid impact. After living for 65.438+600 million years, dinosaurs became extinct.

Dinosaurs are diverse and dominant terrestrial vertebrates in Mesozoic. The word "dinosaur" is a biologist's translation of English Dinosauria, that is, "scary lizard", rather than "dragon" in China's traditional culture. Dinosaurs once ruled the global terrestrial ecosystem for more than 65.438+0.6 billion years. Dinosaurs first appeared in the late Triassic 230 million years ago and stood out in the Great Extinction. They died at the end of Cretaceous about 65 million years ago. 186 1 The archaeopteryx fossils found are very similar to the megagnathus fossils, but the difference is that the archaeopteryx fossils have feather traces [1], indicating that birds may be descendants of dinosaurs.

Since 1970s, many studies have pointed out that modern birds are probably the direct descendants of theropod dinosaur Deinonychus. Most scientists regard birds as the only dinosaurs that have survived and developed to this day, and a few even advocate that they be classified into the same category.

Crocodiles are modern close relatives of another kind of dinosaurs, but their relationship is farther than that between dinosaurs and birds. Dinosaurs, birds and crocodiles all belong to the main evolutionary branches of reptiles, which first appeared in the late Permian and became the dominant groups of amphibians in the middle Triassic.

Dinosaurs (excluding birds) are a main group of dragon reptiles living on land. Their limbs stand upright under their bodies instead of extending to their sides. [2] Many prehistoric reptiles are often informally identified as dinosaurs by the general public, such as pterosaurs, ichthyosaurs, plesiosaurs, black dragon and Panlong (Allosaurus and pterosaurs), but from a scientific point of view, these are not dinosaurs.