Dinosaurs are Mesozoic reptiles, which appeared 245 million years ago and flourished 65 million years ago. Or both dinosaurs and plesiosaurs and pterosaurs. Dinosaurs suddenly disappeared in a certain period, which became a mystery in the evolution history of life on earth, and no one has solved it 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 dinosaur fossils at all. It can be inferred that dinosaurs died out together in Mesozoic.

There are many kinds of dinosaurs, and their shapes and habits are quite different. Among them, the big one can be as big as dozens of elephants combined; Small, but almost like a chicken. As far as food habits are concerned, dinosaurs have mild vegetarians and fierce carnivores, and there are omnivorous dinosaurs that eat both vegetarian and vegetarian foods.

The real reason for the extinction of dinosaurs has been debated since ancient times, but there is no definite statement, so it is still an unsolved mystery. Here are only some well-known statements as follows:

1. meteorite collision theory:

65 million years ago, a huge meteorite hit the earth, making the dinosaurs that lived in King's Landing 1 100 million years extinct. This theory was put forward by four scientists, including Dr. Luis Albales of the University of California, Berkeley.

This huge meteorite is about ten kilometers in diameter. The crater caused by the impact is 200 kilometers in diameter. The energy generated by the impact, if converted into a yellow explosion, is equivalent to one million tons. Dust diffuses into the stratosphere through the atmosphere. It caused the darkness of the earth for months. During this period, many creatures, led by dinosaurs, became extinct.

2. Comet collision theory;

The "comet collision theory" is based on paleontologist David? Rapp and John? Sepkovsky's argument that "the extinction of paleontology occurs every 26 million years" is the beginning. Louis? Albalez gave this argument and his own theory to the astrophysicist-Charlie? Milla, later believed by Milla, periodically pushed comets to the earth because of the gravitational force of Nemesis, the half star of the sun.

3. Theory of orogeny;

At the end of Cretaceous, the swamp was dried up by orogeny, and many dinosaurs whose home was swamp could no longer survive. Because of the changes in the post-Qi Dynasty, plants also changed, and herbivorous dinosaurs could not adapt to new foods and died out one after another. The herbivorous dinosaurs became extinct, and the carnivorous dinosaurs also lost their dependence. As a result, they also became extinct. This extinction process lasted 65,438+0,000-20 million years. By the end of Cretaceous, it was extinct on the earth.

4. Climate change theory:

As a result of plate movement, ocean currents change, which leads to great changes in climate. The cold climate killed plants and dinosaurs died for lack of food.

5. Volcanic fire theory:

Because the volcano erupts, it spews a lot of carbon dioxide, causing the global greenhouse effect and causing food death. Moreover, the volcano spewed fire, resulting in the release of a large amount of salt, the destruction of the ozone layer, harmful ultraviolet radiation on the surface, resulting in extinction.

The theory of ocean ebb tide with intransitive verb;

According to Barker, when the ocean ebbs and the land borders, creatures contact each other, which leads to the extinction of some species. Kangaroos, for example, can live in the island continent of Europe, but they will die if they meet other animals in South America.

In addition to this relationship between eating and being eaten, there are also infectious problems such as diseases and parasites.

Seven. Warm-blooded animals say:

Some people think that dinosaurs were warm-blooded animals, so they could not bear the cold weather in the late Cretaceous and could not survive. Because even if dinosaurs were warm-blooded, their body temperature was still not high, probably similar to that of living sloths, and to maintain such a body temperature, they could only live in a tropical climate. At the same time, the dinosaur's respiratory organs were not perfect and could not fully supplement oxygen. They don't have thick hair to avoid hypothermia, but they easily lose a lot of heat from their long tails and feet. The difference between warm-blooded animals and cold-blooded animals is that if the body temperature drops below a certain range, it will consume physical energy to raise the body temperature and the body will soon become weak. They are too big to go into caves to avoid the cold, so if the cold days last for a few days, they may freeze to death because of exhaustion.

Eight. Fratricidal theory:

Some people think that the real reason for the extinction of dinosaurs is the result of their killing each other-carnivorous dinosaurs ate herbivorous dinosaurs, carnivorous dinosaurs increased, herbivorous dinosaurs naturally became less and less, and finally disappeared. Carnivorous dinosaurs killed each other because they had no meat to eat, and finally died together.