How many years did dinosaurs live?

The life span of animals is often related to their growth patterns. Animals with unlimited growth live longer than animals with limited growth. If the unlimited growth mode of living animals is applied to the study of dinosaurs, the time required for some groups of dinosaurs to hatch from eggs to adulthood is 26 -38 years in protoceratops, 82- 1 18 years in medium sauropods and more than 100 years in giant sauropods, such as brachiosaurus. Then, if you grow into an adult dinosaur and live for the same time, Brachiosaurus can live for about 300 years.

Dinosaurs are Mesozoic reptiles, which appeared 245 million years ago and flourished 65 million years ago. Or both dinosaurs and plesiosaurs and pterosaurs. 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 dinosaur fossils at all. It can be inferred that dinosaurs died out together in Mesozoic.

Reasons for the extinction of dinosaurs

Since ancient times, there have been different opinions about the real cause of dinosaur extinction, 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:

1980, American scientists found a high concentration of iridium in the stratum 65 million years ago, which was dozens or even hundreds of times higher than the normal content. Such a high concentration of iridium can be found in meteorites, so scientists associate it with the extinction of dinosaurs. According to the content of iridium, it is also calculated that the impact object is an asteroid with a diameter of 10 km. Such a large meteorite hit the earth. It's definitely an unparalleled blow. According to the earthquake intensity, it is about Richter scale 10, and the diameter of the crater produced by the impact will exceed 100 km. It took scientists 65,438+00 years and finally got the preliminary results. They found this crater in the stratum of Yucatan Peninsula in Central America. According to the calculation, the diameter of this crater is 65438+.

_ _ _ Scientists began to describe the heroic scene 65 million years ago for us. One day, dinosaurs were still eating and drinking carefree in paradise on earth. Suddenly, a dazzling white light appeared in the sky, and a boulder with a diameter of 10 km fell from the sky. It was an asteroid that fell into the sea at a speed of 40 kilometers per second and hit a huge one at the bottom of the sea. Steam sprayed tens of thousands of meters into the sky, and then the tsunami was as high as 5 kilometers and spread at an extremely fast speed. The turbulent sea swept everything that landed on land, and the turbulent waves swept the earth's surface, and then merged at the back end of the impact point. The huge sea power triggered a strong volcanic eruption in Deccan Plateau here, which changed the movement direction of the earth plate. What a terrible disaster this is. Meteorites hit the earth and produced a lot of dust. The polar snow melts, plants are destroyed and volcanic ash fills the sky. For a time, the sky was dark, the temperature plummeted, and it rained heavily. Mountain torrents and mudslides swept away the dinosaurs and buried them. In the next few months or even years, the sky is still dusty and overcast, and the earth enters a low temperature because it has not seen the sun all the year round, and the vast land is silent for a while. Therefore, an era in the history of biology is over.

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:

Because of the climate problem, a large number of flowers and plants died out, so that herbivores gradually died, while carnivores died out because of lack of food.

Nine. Oppression theory:

The rapid increase in the number of dinosaurs led to the extinction of herbivorous dinosaurs with limited plants, and then carnivorous dinosaurs that ate herbivorous dinosaurs died because of lack of food. (Doubt: Why did dinosaurs suddenly increase after about 200 million years of ecological balance? The key to the establishment of this theory has also directly caused many scholars to review the reasons for the abnormal increase in dinosaur production. )

10. The mammalian prisoner said:

In the second half of Mesozoic, the ancestors of mammals existed. According to fossil records, mammals at that time were very small and the number was very limited. It was not until the late Cretaceous that the number began to increase rapidly. It is speculated that they are omnivores whose main food is insects. These small mammals have been eating dinosaur eggs since they found them.

1 1. The aging theory of species;

People think that the dinosaur's body was too big because it flourished for hundreds of millions of years. Moreover, bones such as horns are also extremely developed, which causes great inconvenience to life and eventually leads to extinction.

The most representative dinosaur brontosaurus is 25 meters long and weighs 30 tons. Because of his huge size, he lost his ability to survive. In addition, Triceratops and others also went to the road of self-destruction because of their expanding three horns and unusually developed bones to protect their heads.

My opinion: not all dinosaurs are so huge, but there are also small dinosaurs with a body length of only about one meter. In addition, there are dinosaurs with bones like deer that can run briskly. But why did this dinosaur die out at the same time? Moreover, in cold-blooded animals, abnormally developed bones and other parts are considered to be able to absorb external temperature and release internal heat to regulate body temperature, which has very favorable functions. Therefore, I suspect that the extinction of dinosaurs was due to the aging of species. )

Twelve. Alkaloid theory:

According to this theory, flowering plants began to appear in the last period of dinosaur existence, that is, the Cretaceous period, and some of them contained toxic alkaloids. Dinosaurs died of poisoning because of eating a lot of food. Because mammals can distinguish poisonous plants through taste and smell, but dinosaurs don't have this ability.

However, plants containing alkaloids did not suddenly appear in the late Cretaceous, but were already visible five million years before the extinction of dinosaurs. This theory can't explain why dinosaurs survived during this period.

In addition to the above twelve statements, there are other less well-known statements, such as "infectious diseases", "radiation from the universe or supernova explosion", "not taking Noah's Ark" and "vibration theory of the solar system". As for which is the best statement, it depends on everyone's ideas, and there is no right or wrong. After all, the mystery of dinosaur extinction has not really been solved!

In the dinosaur extinction hypothesis, the asteroid impact theory is the most popular. According to this theory, asteroids (later scholars thought comets were more likely) were the culprit in killing dinosaurs. The asteroid impact theory was put forward by American physicist Alvarez and others in 1979. They believe that 65 million years ago, an asteroid with a diameter of about 10 km collided with the earth, causing a violent explosion. A lot of dust was thrown into the atmosphere, which blocked the sun for several months. The earth was dark and cold, plants died, the food chain was interrupted, and many animals, including dinosaurs, became extinct.

The main evidence of asteroid impact theory is:

1。 Iridium anomalies have been found in the clay layer at the boundary between Cretaceous and Tertiary, which has been studied all over the world, and its content is several tens to hundreds times higher than that in the crust. Iridium is rare in the earth's crust, but it is abundant on asteroids. Therefore, it has been suggested that the iridium-containing clay layer on the boundary is formed by the rapid fall of dust raised by asteroids when they hit the earth.

2。 Micro-glass spherulites and shocked quartz caused by impact are found in the boundary clay layer.

3。 A huge crater was discovered in Yucatan Peninsula of Mexico, the United States and Siberia. Their age is about 65 million years old. 1995, it is reported that a larger crater was found in India. It is estimated that the diameter of the small celestial body that caused this crater should be not less than 40 kilometers.

4。 1995, a scientist found a huge dinosaur tomb on the Cretaceous-Tertiary boundary in Khhoda, India, where countless different kinds of dinosaur fossils piled up together. It is speculated that this is the dinosaur remains that died suddenly when a small celestial body hit the earth.

But in recent years, there is a lot of evidence that there may have been an asteroid impact 65 million years ago, but dinosaurs were extinct in most areas before the arrival of asteroids. In some areas, a small number of dinosaurs may have survived after the impact, but they soon became extinct. At best, the asteroid impact made the last group of extinct dinosaurs worse.