Dinosaurs are the largest animals in the world. It appeared about 2. 1 100 million years ago and finally magically became extinct. Everything we know about dinosaurs today comes from dinosaur fossils.

There are many kinds of dinosaurs. According to the shape of their skeletal fossils, they can be divided into ornithosaurus and sauropods, and according to their tooth fossils, they can also be divided into carnivores and herbivores. Dinosaurs are not only varied, but also amazing in shape. Some of them fly in the sky, some swim in the water, and some crawl on land. A big one can be as big as dozens of elephants combined; Small, but almost like a chicken.

So far, the largest dinosaur we have found is Zhenlong, which is 39 to 52 meters long! The height can reach 18 meters! ! The weight reaches 130 tons! ! ! If such a behemoth walks on the night of January, every time its giant feet step on the ground, it will make the earth tremble, just like an earthquake, so it is called "Zhenlong".

Dinosaurs ruled the earth for a long time until they suddenly became extinct 65 million years ago. Scientists have been arguing endlessly about the reasons for the extinction of dinosaurs. There are two main viewpoints: one is "small celestial body impact theory". 65 million years ago, a meteorite hit the earth, which led to volcanic eruption and great changes in the earth's climate, and finally made dinosaurs extinct on the earth; The other is "volcanic eruption theory", that is, volcanic groups erupt, spewing lava slurry, and then the world of ice and snow comes, leading to the extinction of dinosaurs.

As for the real reason for the extinction of dinosaurs, there is no answer yet, which will be a mystery in human hearts. Let's explore the secrets of science! Come back to answer this secret later!

Why did dinosaurs become extinct?

One day 65 million years ago, the green jungle was bathed in the scorching sun and was peaceful. Some dinosaurs gathered near the jungle, some of them chased each other, some were quietly devouring fresh leaves, some triceratops snuggled together to rest, and two hadrosaurs walked around the nest, carefully guarding their unborn babies. In the shadow of the jungle not far away, there is a Tyrannosaurus Rex. Its fierce eyes stare at everything in front of it, looking for opportunities to pounce on the target it is interested in.

Suddenly, a dull thunder broke the peace of the jungle. Hadrosaurs first craned their necks warily, and their voices grew louder and louder. It shook the earth and brought an ominous omen. Triceratops jumped up quickly, but it was too late. The earth is shaking, like a mountain of boulders falling from the sky, surrounded by smoke, clouds of smoke rising from the ground. In an instant, the boundary between heaven and earth disappeared, darkness was everywhere, and the world seemed to come to an end. Within a few days, the earth's surface was completely covered with smoke and dust, covering the sky, the temperature plummeted and darkness enveloped the earth. Without sunshine, plants withered, a large number of dinosaurs suffocated and died, and those who survived by luck fell down one after another because there was no food to eat. The earth is full of dinosaur bodies and bones.

This is the story that scientists told us about the extinction of dinosaurs. At that time, many asteroids hit the earth. The strong impact not only left a crater with a diameter of about 200 kilometers on the earth's surface, but also caused the high temperature and high pressure generated during the impact to vaporize the material, thus making the earth's surface constantly full of dust, leading to a large number of animal and plant deaths and the disintegration of the biological chain. Dinosaurs died out after this sudden disaster. A few dinosaurs may have narrowly escaped a temporary disaster, but they won't last long, because the environment on which they live has been completely destroyed and it will take a long time to recover, and only death awaits them.

The theory that asteroids hit the earth is not a woven myth, and the enrichment of iridium in the stratum is an important scientific basis. It turns out that the content of iridium on the earth is very small, only concentrated in the depths of the core. Where does a small amount of iridium in the formation come from? Through in-depth study, scientists believe that these iridium should come from cosmic dust. In the late 1970s, a high concentration of iridium was found in the clay layer on the Cretaceous-Tertiary boundary in Italy, which coincided with the extinction time of dinosaurs. Subsequently, during this period, the iridium content in the strata was found to be abnormal in many parts of the world, so the hypothesis that whisperd hit the earth and made iridium exist in the strata was proved. According to this hypothesis, geologists began to look for iridium anomalies around the world, and more and more evidence supported this hypothesis. It has become an acceptable theory that asteroids hit the earth and led to the extinction of dinosaurs. Information from astronomical observations shows that more than 2,200 asteroids have been discovered and named in the solar system, and there is no doubt that they have the opportunity to "visit" the Earth. It is also calculated that when an asteroid falls to the earth, the energy released by the impact is equivalent to hundreds of atomic bombs and hydrogen bombs exploding at the same time, and hundreds of tons of soil and dust may be thrown into the air, leaving the earth in darkness and disorder for at least several months or even longer. It seems that the extinction of dinosaurs is an act of god.

There are many other hypotheses about the extinction of dinosaurs. For example, the "Nemesis Hypothesis", that is, the theory of comet impact. It is believed that when a comet in the solar system is disturbed by the gravity of a companion star, it will produce thousands of "storms", and some of these "storms" will spread to the earth, so that the earth will suffer a trauma every once in a while (about 26-30 million years), and dinosaurs will die because of this continuous blow. Related to the hypothesis that the universe brings disaster, there are supernova explosion theory and solar flare hypothesis. In recent years, some new hypotheses have emerged, such as the "canceration theory" that dinosaurs were caused by the penetration of neutrinos in outer space, and dinosaurs were probably collectively extinct after suffering from various cancers. All these hypotheses are dinosaur extinction theories that emphasize extraterrestrial factors, but the causes of dinosaur extinction can not be ignored. The earth entered the late Mesozoic, and the living environment changed greatly. The development of dinosaurs has reached its limit and it can't adapt well to new conditions. Although dinosaurs ruled for a while, with the arrival of a new era, they had to give way to emerging mammals.

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The extinction of dinosaurs was 65 million years ago. Moreover, at that time, not only all kinds of dinosaurs that ruled the earth for more than 100 million years were extinct, but also the tragic fate came to many other creatures living on the earth's land, sea and sky. Also extinct in this disaster are marine reptiles such as plesiosaur, flying reptiles such as pterosaurs, relatives of terrestrial reptiles such as colorful lizards, and marine invertebrates such as ammonites and arrowheads. As for the micro-phytoplankton in the ocean, calcareous planktonic foraminifera and calcareous micro-phytoplankton have also been almost swept away. After this catastrophe, about 50% of the biological genera and almost 75% of the biological species on the earth disappeared from the earth forever. This is really a mass extinction and catastrophe. Due to the extinction of species, the face of the biological world on earth changed fundamentally about 65 million years ago. This extinction marks the end of Mesozoic era, and the geological history of the earth has entered a new era-Cenozoic era. Through unremitting efforts, scientists have analyzed and studied all the clues that can be found at present and put forward various theories to explain this extinction phenomenon. But so far, there is still no 100% correct answer about the cause of this extinction. Perhaps, such an answer is waiting for you to find. 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, only some well-known statements are described as follows: meteorite collision theory: 1980, American scientists found high concentration of iridium in the strata 65 million years ago, and its content exceeded the normal content by dozens or even hundreds of times. Therefore, scientists linked it to the extinction of dinosaurs. According to the content of iridium, it is calculated that the impact object is an asteroid with a diameter of 10 km. Such a large meteorite hit the earth, which is definitely an unparalleled blow. According to the earthquake intensity, it is about Richter scale 10. The crater produced by the impact will be more than 65,438+000 kilometers in diameter. It took scientists 65,438+00 years to finally get 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 between180km and 300km. Now, scientists are still doing further research on this big pit. _ _ _ Scientists began to describe the heroic scene 65 million years ago for us. One day, dinosaurs were still eating and drinking in paradise on earth, and suddenly a dazzling white light appeared in the sky. A boulder with a diameter of 10 km fell from the sky. It is an asteroid with a speed of 40 kilometers per second. The seabed was knocked out of a huge pit, and the seawater was rapidly gasified, and the steam was sprayed into the sky for tens of thousands of meters. 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 met at the back end of the impact point, where the huge sea power triggered a strong volcanic eruption on the Deccan Plateau. At the same time, it changed the movement direction of the earth's plates. What a terrible disaster this is. Meteorites hit the earth and produced overwhelming dust, polar snow melted, plants were destroyed and volcanic ash filled the sky. For a time, it was dark and the temperature plummeted. Heavy rain, flash floods and mudslides swept away the dinosaurs and buried them. In the next few months or even years, the sky is still full of dust and clouds, and the earth is buried all the year round. The vast land was silent for some time. Thus an era in the history of biology ended. The orogeny said: The orogeny at the end of Cretaceous dried up the swamp, and many dinosaurs whose home was the swamp could no longer survive. Because of climate change, plants have also changed, and herbivorous dinosaurs were unable to 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. Climate change theory: due to plate movement, ocean currents change, which causes great changes in climate. The cold climate killed plants and dinosaurs died for lack of food. 4. Volcanic eruption theory: Due to volcanic eruption, a large amount of carbon dioxide is ejected, which impacts the global greenhouse effect and causes 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. Antonio Cikic, a famous Italian physicist, recently suggested that the extinction of dinosaurs was probably caused by a large-scale submarine volcanic eruption. Professor Qi Jichi believes that at the end of Cretaceous, a series of large-scale volcanic eruptions occurred on the earth under the ocean, which affected the thermal balance of seawater, and then caused the change of land climate, thus affecting the survival of dinosaurs and other animals that needed a lot of food to survive. His reason is that the impact of modern submarine volcanic eruption on the ocean and atmosphere is well known, but its impact is far less than that of submarine volcanic eruption 65 million years ago. Professor Qi Jichi believes that in the past, the scientific community knew very little about submarine volcanic eruption, and now it is necessary to conduct in-depth research on this phenomenon that seriously affects the earth's environment. For example, he said that Greenland once had dense vegetation, but when the global ocean water temperature balance changed, the cold ocean current changed direction and crossed Greenland, thus turning this big island into a land covered with snow and ice. This is a typical example that the change of ocean water temperature balance has a great influence on climate. Submarine volcanic activity is an important factor affecting the balance change of ocean water temperature. Therefore, Professor Zichichi believes that the change of ocean water temperature balance caused by large-scale eruption of submarine volcano should be taken as an important reference factor for studying dinosaur extinction. Ocean ebb tide theory: According to Barker, when the ocean ebbs and the land borders, creatures contact each other, leading 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. Warm-blooded animals said: Some people think that dinosaurs are warm-blooded animals, so they may not be able to resist the cold weather in the late Cretaceous and thus cannot 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. Killing each other said: because of the climate problem, a large number of flowers and plants died out, leading to the gradual death of herbivores, while carnivores died because of lack of food.

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I will give you an explanation about dinosaur eggs. I hope you like the Paleontology Expo-dinosaur egg dinosaur is a reptile, and it lays eggs like most other reptiles. It is obviously more difficult to preserve eggs as fossils than bones and teeth, because eggshells are too brittle to be broken when touched, let alone preserved in rock formations for 60 to 70 million years! However, the size of the world is amazing. Some dinosaur eggs were preserved as fossils after all, which were reported as early as 1920s. Because it was still rare at that time, it was extremely precious! Later, new discoveries were made all over the world, and China became richer. As far as we know, China is from Guangdong in the south, Inner Mongolia in the north, Xinjiang in the west and Zhejiang and Anhui in the east, so that dinosaur eggs are produced in more than a dozen provinces. Its wide distribution and large quantity make it the first in the world. We not only have an egg fossil, but also a bird's nest. Sometimes there are as many as twenty or thirty birds in a nest, and the upper and lower floors overlap and are arranged in concentric circles. It's really beautiful! I remember when the author rambled about dinosaur eggs with my teacher Professor Yang in his early years, he asked: Does a dinosaur lay dinosaur eggs at one time or accumulate them many times? Did dinosaurs lay their eggs from the center of concentric circles or from the outside? Because there was no real evidence, the author handed in a blank sheet of paper. I wonder if readers can answer? There is also an interesting phenomenon about dinosaur eggs, that is, the places where dinosaur skeleton fossils are produced often have no dinosaur egg or a small number. On the contrary, where there are many oviparous fossils, there are often no dinosaur fossils or not many. Why is this? Some people explained that these egg fossils have not yet broken their shells, and they are "bad guys" who can't hatch small dinosaurs, so there are more eggs and fewer dragons. On the other hand, all the eggs that hatched small dinosaurs have been broken, and it is impossible to preserve them as complete egg fossils. So there are more dragons and fewer eggs. Naturally, this is just a "family statement", which is right and wrong, and it remains to be confirmed. The study of dinosaur eggs, like dinosaur footprints, is a branch of vertebrate paleontology. It mainly focuses on the exploration of the shape and structure of the egg itself, and pays less attention to what kind of dinosaur laid the egg. Because eggs and dinosaurs are usually preserved as fossils, even eggs without dinosaurs, it is difficult to determine the owner of eggs. Just like how many chickens you have at home, if you didn't see them with your own eyes, can you tell exactly which chicken laid an egg? Therefore, in paleontology, the genus and species identification of egg fossils is self-contained, which is not consistent with the genus and species of dinosaurs. China's research on dinosaur eggs began with Professor Yang. According to the morphological structure of egg fossils, he ordered several genera and species such as long eggs, round eggs and coarse preserved eggs. Only at the end of the paper, he discussed that an egg might have been laid by some kind of dinosaur. With the development of science and technology, the research on dinosaur eggs has moved from the outside to the inside. Scholars not only pay attention to the external structure of eggs, but also observe the fine structure of egg skins at all levels through grinding and photomicrography. Found different egg fossils, egg skin structure is different, indicating that it was produced by different dinosaurs. More significantly, according to the change of the thickness and microstructure of the egg skin, we can discuss the adaptability and hatching success rate of different egg fossils to the environment at that time, and then clarify the reasons for the decline and extinction of dinosaurs. In recent years, there have been new discoveries of dinosaur eggs in China, especially in Xixia County, Henan Province. According to recent reports, tens of thousands of dinosaur eggs have been produced, which is really a "world miracle"! Even more exciting, it is said that life science scholars in China obtained the DNA of dinosaur gene fragment from a broken dinosaur egg. As soon as the news spread, newspapers and magazines publicized it one after another, which became one of the hottest topics in the scientific and technological circles at that time. Some people compare its importance to the discovery of the first skull in Beijing, and some people hope to copy dinosaurs! However, some people suspect that this DNA is really in this egg? Now that the egg is broken, it is difficult to guarantee that it will be "polluted" by other creatures! What is the result? Science will definitely give us a correct answer.