Dinosaurs lived on the earth for about1.65 ~1.700 million years. Dinosaurs appeared in the middle and late Mesozoic Triassic about 240 million years ago. The earliest dinosaur found in the world is also the most primitive dinosaur, which lived 234 million years ago. Its fossils were found in Argentina, South America. Dinosaurs died out at the end of the Mesozoic Cretaceous about 65 million years ago after experiencing the Triassic, Jurassic and Cretaceous in Mesozoic. So * * * lived on the earth for about 1.65 million years.
Dinosaurs refer to all the descendants of the recent ancestors of Triceratops (Pterosaur) and modern birds (Diptera), all of which are extinct except birds. The biggest difference between dinosaurs and other reptiles lies in the posture of standing and the way of marching. Dinosaurs are completely upright, with their limbs directly under their bodies. This structure has advantages over other reptiles in walking and running.
Dinosaur extinction theory
1, continental drift theory: geological research proves that there was only one continent on the earth, namely Pangaea, when dinosaurs lived. Due to the change of the earth's crust, this continent split and drifted greatly in Jurassic, which eventually led to the change of environment and climate and the extinction of dinosaurs.
2. Geomagnetic change theory: Modern biology has proved that the death of some creatures is related to the magnetic field. When the earth's magnetic field changes, creatures sensitive to the magnetic field may lead to extinction. Scientists infer that the extinction of dinosaurs may be related to the change of the earth's magnetic field.
3. Gender imbalance theory: Due to the cold weather, most of the young male dinosaurs hatched by dinosaur mothers have caused a serious gender imbalance in the dinosaur world. With the gradual decrease of female dinosaurs, the dinosaur family went extinct.
4. Acid rain: There may be strong acid rain at the end of Cretaceous, which dissolved trace elements including strontium in the soil. Dinosaurs ingested strontium directly or indirectly through drinking water and food, causing acute or chronic poisoning and eventually dying in batches.
5. Theory of Species Struggle: At the end of the dinosaur era, the first small mammal appeared. These animals are rodent carnivores and may feed on dinosaur eggs. Due to the lack of natural enemies, more and more small animals eventually ate dinosaur eggs, leading to the extinction of dinosaurs.