Continue to study the reasons for the extinction of dinosaurs. For a long time, the most authoritative view is that the extinction of dinosaurs 65 million years ago was a huge meteorite. According to research, when an asteroid with a diameter of 7- 10 km fell to the earth's surface, it caused a big explosion and threw a lot of dust into the atmosphere. The dust cloud formed by the clouds temporarily stopped the photosynthesis of plants and the extinction of dinosaurs.
? The asteroid impact theory was quickly supported by many scientists. In the KT boundary layer, some scientists found that iridium is rare on the earth and many other planets. 199 1 year, a very long period was found in the crater of Yucatan Peninsula in Mexico, which further confirmed this statement. Today, this view seems to be a foregone conclusion.
? However, many people are skeptical about this asteroid impact theory, because the fact is that frogs, crocodiles and many other temperature-sensitive animals endured and survived the Cretaceous period. This theory can't explain why only dinosaurs died. So far, scientists have put forward the reasons for the extinction of dinosaurs. There should be more than a dozen exciting and dramatic meteorite impacts, saying, "Only once.
? Say: "meteorite impact", the main point of view about dinosaur extinction, has the following contents:
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Climate change.
? 65 million years ago, the earth's climate changed suddenly and the temperature dropped, which led to the decrease of oxygen content in the atmosphere and dinosaurs could not survive. Some people think that dinosaurs were cold-blooded, but without hair and warm organs, they could not adapt to the temperature drop of the earth and froze to death.
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Species struggle.
? At the end of the dinosaur era, the first small mammals appeared. These animals were rodent carnivores and probably ate dinosaur eggs. Due to the lack of natural enemies of this small animal, more and more people end up eating dinosaur eggs.
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Third, continental drift theory.
? Geological research has proved that the only continent that existed in the dinosaur era was only one earth, namely "Pangea". Continental division and drift occurred in Jurassic. Due to the change of the earth's crust, the environment and climate eventually changed and dinosaurs became extinct.
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Geomagnetic variation.
? Modern biology has proved that the death magnetic field of some organisms. The change of magnetic field sensitive organisms in the earth's magnetic field may lead to extinction. It is inferred that the extinction of dinosaurs may be related to the change of the earth's magnetic field.
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Angiosperm poisoning.
At the end of the dinosaur era, gymnosperms on the earth gradually disappeared and were replaced by a large number of angiosperms. Gymnosperms do not contain toxins in these plants. Giant dinosaurs had a huge appetite. Where did the toxins accumulated in their bodies from eating angiosperms come from? Excessive and final poisoning.
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Acid rain.
? In the late Cretaceous, it may have suffered from strong acid rain, trace elements and strontium dissolution in the soil. Dinosaurs ingested strontium directly or indirectly through drinking water and food, were poisoned acutely or chronically, and the last batch died.
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Seven, meteorite impact.
? Cretaceous dinosaurs, because they were cold-blooded animals, the temperature dropped to night. At the end of Cretaceous, groups of small mammals ate collectively, could not move freely and died, and slowly entered the road.
? Chicxulub crater is located in chicxulub crater, Yucatan Peninsula. Like the extinction of dinosaurs 65 million years ago? The answer lies in the white rock layer.
? This layer of rock is called KT boundary by geologists, which means the marker line of Cretaceous-Tertiary boundary. The rocks at the bottom are rich in dinosaur fossils, but above the KT line, dinosaurs disappeared.
? The rocks at the KT boundary contain iridium, which is a rare metal, with an average content of only one billionth of the earth. However, the iridium content of the formation is 200 times of the normal content. Where can I find so much iridium? In space.
? The content of iridium is 1000 times higher than that of the earth. At the same time, evidence of shocked quartz was found on this white rock, which is the only imprint left by the asteroid. High concentrations of iridium and Shi Ying, tertiary boundary rocks in many parts of the earth. The trace of the world can only come from the most violent impact. Where is the influence now? Yucatan Peninsula in Mexico.
? 65 million years ago, this was a very violent impact, which was unmatched by any event in human history. The time when an asteroid or comet hit the earth was about 6 miles wide. Its propagation speed on the earth's surface is more than 40 times the speed of sound. This is a very large amount, so when it hits the earth, the front end meets the surface tail at a height of 300.05 million feet, which is equivalent to the flying height of the plane. A rock as big as a mountain hit the earth.
? There are far more than a few hypothetical reasons for the extinction of dinosaurs. However, these hypotheses have more supporters in the scientific community. Of course, the above method is not perfect. For example, "climate change" does not specify the reasons for climate change. After examination, the osteophytes of some small dinosaurs competed with the early species of small mammals, saying, "There are loopholes to drill. Modern geology believes that "continental drift theory" itself is still a hypothesis. "Angiosperm poisoning" and "acid rain" said that "there is also a lack of sufficient evidence. Therefore, the real reason for the extinction of dinosaurs is further explored by the people of the whole country.
? Questioning and explaining the extinction of dinosaurs
? Many species on our planet appear and then disappear, which is an inevitable stage in the history of biological evolution. However, why such a huge dinosaur-dominated family suddenly disappeared from the earth has aroused our speculations. Scientists have been arguing about what happened at the end of Cretaceous 65 million years ago and what caused the mass deaths of all dinosaurs and other creatures. Some people say that the earth's geological orogeny took place at that time, because many mountains grew to the plains, and the reduction of swamps and wetlands made the climate less humid and warm. Breathing dinosaurs can't adapt to cold, dry, hot and dry air. A dinosaur brought winter food, so we walked into a dead end. Some people say that it caused a strong supernova explosion in the earth's climate change, and the temperature suddenly rose and then dropped very low. It was dinosaurs that ate many flowering plants. Many toxins in these flowers were eaten by dinosaurs, so they were poisoned. The evidence is that when flowering plants. Another wisdom believes that this is because dinosaurs, a huge animal, kept farting because they ate too much and released a lot of methane gas into the air. Because they live for too long, they destroy the destructive climate of the earth's ozone layer. Some people even say that as a result, aliens went to the earth to look for it because they thought dinosaur meat was particularly delicious. The evidence is the dinosaur bones they found in the North Pole, such as laser cutting marks. All kinds of miracles. However, it is generally believed that the meteorite impact theory.
? The history of iridium can be traced back to 65 million years ago. 1980, American scientists found high concentration of iridium, which exceeded the normal content by dozens or even hundreds of times. This concentration of iridium can be found in meteorites, so scientists associate it with the extinction of dinosaurs. According to the iridium content, 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. The calculated intensity of the earthquake is about 10 on the Richter scale, and the diameter of the impact crater exceeds 100 km. It took scientists 10 years to finally find the preliminary results of craters and Yucatan Peninsula formed in Central America. The estimated diameter of the pit is 180 km to 300 km. Now, scientists are still doing further research underground.
? The scene that scientists started 65 million years ago. One day, dinosaurs were a carefree paradise for the earth to enjoy food and drink. A dazzling white light appeared in the sky with a diameter of 10 km, which is equivalent to a big stone falling from the sky in a medium-sized city. This is an asteroid that fell into the sea. Its speed is 40 kilometers per second, and it falls into a huge pit at the bottom of the sea. Seawater vaporizes rapidly, and steam can reach hundreds of thousands of kilometers of high-altitude rapids. Immediately, the tsunami as high as 5 kilometers spread at a great speed, and the flood swept the ground and gathered on the back of the impact point. At the end of the year, the turbulent waves swept across the earth's surface, triggering a strong volcanic eruption. The huge sea water in Deccan Plateau forced the volcano there to erupt. At the same time,
? What a terrible disaster this is. Meteorites hit the ubiquitous dust on the earth, the polar snow melted, plants were destroyed and volcanic ash filled the sky. For a time, the sky was dark, the temperature plummeted, heavy rain, mountain torrents and mudslides swept away the dinosaurs and buried them. In the next few months or even years, the sky will be overcast and the earth will not see the sunny silence all the year round. The end of such an era in biological history.
? Of course, more importantly, the extinction of dinosaurs.
? The rest of the examples.
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Theory of orogeny;
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? The orogeny in the late Cretaceous dried up the swamp, and many families of dinosaurs were swamps and could not be copied alive. As a result of coping with climate change, factories also changed, and herbivorous dinosaurs could not adapt to new foods and died out one after another. The herbivorous dinosaurs became extinct, the carnivorous dinosaurs fell, and as a result, they became extinct. During this extinction process, 1000 to 20 million years ago. By the end of Cretaceous, it will be extinct on the earth.
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climate change
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When the plates move, the changes of ocean currents lead to great changes in the climate. ? The cold and dry climate led to the death of plant dinosaurs and the death of food shortage.
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Volcanic eruption
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? The carbon dioxide emitted by volcanic eruption caused a lot of greenhouse effect, which excited the earth and killed plants. Volcanic eruption and salt release rupture the ozone layer, harmful ultraviolet radiation on the earth's surface, leading to extinction.
? Antonio, a famous Italian physicist, refuted the reason that the recent large-scale submarine volcanic eruption of dinosaurs is likely to cause mass extinction.
? The professor retorted that in the late Cretaceous, a series of large-scale volcanic eruptions occurred on the earth under the ocean, which affected the changes of sea water and land climate in heat balance, and then affected the survival of dinosaurs and other animals that needed a lot of food to survive. His reason is that, as we all know, the modern submarine volcanic eruption, the ocean and atmosphere, is only more influential than the submarine volcanic eruption 65 million years ago.
? The professor refuted the phenomenon that the scientific community knew little about submarine volcanic eruption in the past and seriously affected the earth's environment. For example, he said that Greenland once had lush vegetation, but then the sea temperature was balanced and the global cold ocean current changed direction, from the big island Greenland to the snow-covered land. This is a typical example. The change of ocean water temperature balance has great influence on climate. Submarine volcanic activity is an important factor affecting the balance change of ocean water temperature. Therefore, the change of submarine volcano should be taken as an important reference to study the ocean water-temperature balance caused by large-scale explosion caused by dinosaur extinction.
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When the sea ebbs,
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? Robert Barker believes that during the low tide, the creatures on the land edge contact or influence each other, which leads to the extinction of a certain kind of creatures in the ocean. Such as kangaroos, kangaroos can live in the island's mainland Oceania, meeting the declaration of extinction of other animal species, but in the South American continent. In addition to this relationship between eating and being eaten, dinosaurs are in danger of extinction because they are infected and spread diseases and parasites.
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Theory of warm-blooded animals
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? In the past, all scientists thought that dinosaurs were cold-blooded or warm-blooded animals like other reptiles, but with more and more fossil data, their consciousness changed. Some people think that some dinosaurs may be warm-blooded animals. First of all, they think that some dinosaurs are extremely agile and don't crawl on the ground like snakes, but their hind legs can run on the ground at a speed of 20 to 90 kilometers per hour. This requires a strong heart and a high metabolism, which is obviously impossible for cold-blooded animals. Secondly, the intake of dinosaurs in food is quite large. It is speculated that sauropods weighing 30 tons may have nearly two tons of food to eat every day, and only warm-blooded animals need so much energy. It is also reasonable that it is far lower than the view that herbivorous dinosaurs were separated from carnivorous dinosaurs. In addition, there are some smaller dinosaurs whose bodies are covered with feathers or hair to prevent body temperature loss. Other aspects, such as bones, preliminary research shows that some dinosaurs were warm-blooded animals. The parameters of warm-blooded dinosaurs have been strongly criticized, but the final conclusion is how to draw a conclusion.
? Some people think that dinosaurs were warm-blooded animals, so they probably could not resist the cold climate and could not survive in the late Cretaceous. Even though dinosaurs were warm-blooded, their body temperature was still very high. It may be a sloth with a similar temperature and life span, and it can only survive in a tropical climate at this temperature. Dinosaurs' respiratory organs were not perfect. They couldn't supply enough oxygen and didn't have thick hair to avoid hypothermia, but they easily lost a lot of heat from their long tails and feet. What warm-blooded animals and cold-blooded animals don't like is that if the temperature drops within a certain range, it will affect the ability of the body, increase the temperature of the body, and the body will soon become weak. They are too big to take refuge in caves in cold weather. In the last few days, it is better to run out of the fate of freezing to death. However, the suspicion of this theory, that is, this is a huge dinosaur, and it is impossible to take refuge in caves. This principle has always been imperfect.
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Fratricidal theory
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? Plant extinction, because of climate problems, makes herbivores gradually extinct, while carnivores, because of lack of food, become crazy cannibals and become extinct. (Question: The extinction of plants led to the extinction of dinosaurs. Why are omnivorous dinosaurs that feed on insects on the verge of extinction, while other animals are safe and sound? )
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Oppression theory
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? The number of dinosaurs has soared. In the case of limited factories, if herbivorous dinosaurs have become extinct, living, herbivorous dinosaurs and carnivorous dinosaurs will also die because of lack of food. Question: Why did dinosaurs suddenly increase their ecological balance after about 200 million years? The establishment of this theory directly led to the increase of many scholars' interest in dinosaurs.
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Mammalian evolutionary theory
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? In the second half of Mesozoic, the ancestors of living mammals tried to survive. According to fossil records, there were very few species and limited numbers of mammals at that time. Until the late Cretaceous, the number began to increase rapidly. It is speculated that they are omnivores, mainly eating dinosaur eggs found by insects and other small mammals, and continue to eat them. The breeding crisis eventually led to dinosaurs and led to their extinction.
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Theory of species aging
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? Dinosaurs reached1100,000, and the meat was too big. In addition, abnormal phenomena such as bone angle bring great inconvenience to daily life and eventually lead to extinction.
? The puzzled dinosaur was 25 meters long and weighed 30 tons. The most representative organizations are too large, so they move slowly and lose their viability. The protection devices for the growing triangular bones and other parts of the head are extremely developed, but the way of self-destruction comes from Triceratops.
? (Question: Not all dinosaurs are so huge. They are small dinosaurs with a body length of only about 1 meter. In addition, there are dinosaur bones that can run as fast as deer. But why did this dinosaur become extinct? Extremely developed, bones and other parts, in cold-blooded animals, must be able to absorb external temperature and release heat in the body to regulate body temperature, which has very favorable characteristics. Accordingly, due to the extinction of old dinosaurs, they are skeptical. )
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Alkaloid theory
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? Theoretically speaking, the last stage of dinosaur's vigorous development-Cretaceous, including some types of flowering plants, contained toxic alkaloids and died of poisoning caused by a large number of dinosaurs. Because of the distinction between poisonous plants, mammals, taste and smell, there are no dinosaurs.
However, it suddenly appeared in the late Cretaceous, showing that the plants extinct by dinosaurs 50 million years ago contained alkaloids. This theory does not explain why dinosaurs spent this period. So this statement is not isolated.
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Breeding frustration theory
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? Many ancient reptile egg fossils, dinosaur eggs, have been found in the world. According to the morphological structure, dinosaur eggs can be divided into short round eggs, oval eggs and slender eggs. For large-scale dinosaur eggs, the eggshell thickness and its internal and external "decoration", the structure of spine eggshell and the proportion range of its shell-like columnar layer are different. In order to make dinosaur eggs with internal functions, scientists have adopted new technologies and various methods, such as scanning tunneling microscope, X-ray diffraction (XRD), polarizer and CT scanner. In recent years, Chinese scientists first discovered the damaged fossils of dinosaur eggs in Laiyang City, Shandong Province by using CT technology. The discovery of dinosaur eggs in Laiyang and other methods can't observe dinosaur embryos.
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Climate catastrophe theory
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? According to the information obtained by deep-sea geological drilling, some scientists believe that the abnormal changes on the earth 65 million years ago, the climate and temperature suddenly rose. Cold-blooded dinosaurs with weak cooling ability could not adapt to the environment well, which made their endocrine system dysfunctional, especially causing serious damage to the male reproductive system. As a result, dinosaurs could not reproduce and eventually became extinct.
? There is also a theory that climate change also led to the extinction of dinosaurs, but the process of speculation is different. Scholars of this school believe that about 700,000 years ago, the land between the Arctic Ocean and other oceans was completely separated. In the last days, due to various factors, salt water gradually turned into fresh water. Until 65 million years ago, the separated Arctic Ocean and other ocean "dikes" suddenly broke out. A lot of different light is desalinated in the Arctic Ocean, and water flows into the ocean. The water temperature in the Arctic Ocean is low, and these "overflowing" cold water forms a layer of cold current, which makes the sea water temperature of the earth drop rapidly to about 20 degrees. Ocean temperature and continental climate have a serious influence on the cooling of continental air. At the same time, the rapid reduction of water vapor in the air has caused a large area of arid land. Climate change is the comprehensive influence of dinosaur extinction on land structure.
? A possible way of climate change leading to the extinction of dinosaurs has seriously affected dinosaur eggs. Some scientists have found that before the extinction of dinosaurs in the late Cretaceous, the eggshells of dinosaur eggs became thinner. Because of the rapid climate change, dinosaurs became extinct on a large scale. Our paleontologists also found that dinosaur eggs exported from some fossil sites are on the verge of extinction, and the pores of dinosaur egg eggshells are less than those of other periods, which is probably related to cold and dry climate change.
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Changes of atmospheric composition theory
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? The extinction of dinosaurs in the late Cretaceous is an eternal mystery in the history of biology. Scientists have put forward a theory to explain why, but there has never been a conclusion acceptable to everyone. The popular saying is that the disaster caused by the asteroid hitting the earth led to the extinction of dinosaurs, but this theory is not perfect. Dinosaurs are the most successful animals on earth, with different sizes, shapes and sizes, rich expressions and lifestyles. If the asteroid that caused the extinction of dinosaurs hit the earth and caused disaster, then why did birds escape the disaster and survive to the present? This can't help but urge people to look for other ideas and analyze the reasons for the extinction of dinosaurs.
Modern scientific analysis, we know that in the distant era, the earth has just formed, there is basically no oxygen in the air, and the carbon dioxide content is high. Later, the photosynthesis of autotrophs absorbed carbon dioxide and produced oxygen, which changed the atmospheric environment of the earth. At the same time, on the one hand, through the biological fixation of carbon dioxide on coal, oil is deposited in the stratum, on the other hand, through the process of various organic or inorganic carbonates deposition. This testimony has been completed.
There is evidence that dinosaurs lived in Mesozoic, but the concentration of carbon dioxide in the subsequent Cenozoic was low. ? Changes of atmospheric composition and extinction of dinosaurs?
As we all know, every living thing needs to be able to live normally in an appropriate environment, and environmental changes can often lead to the rise and fall of a species. When the environment is beneficial to this species, it will flourish, otherwise, it will decline or even become extinct. Environmental factors include temperature, water and other factors, including the composition of the atmosphere. Will the change of atmospheric composition affect the life span of living things? The answer is yes. For example, people with high carbon dioxide concentration in the environment will be in danger, and some animals are even more sensitive to the change of carbon dioxide concentration than people.
? Mesozoic dinosaurs lived in an environment with high carbon dioxide content in the atmosphere, and dinosaurs adapted to the atmosphere with high carbon dioxide concentration. Maybe only in that atmosphere can they live a good life. Although mammals have appeared, they have not developed greatly, probably because the environment such as atmospheric composition is not ideal, so they have been in a weak position and developed slowly in Mesozoic. With the passage of time, by the end of Cretaceous, great changes had taken place in the atmospheric environment, with the decrease of carbon dioxide and the increase of oxygen content. This bad environment of dinosaurs may be reflected in two aspects: 1, dinosaurs are unwell, and in a new environment, they are easy to get sick, and diseases will spread like a plague. As shown in Figure 2, mammals are more suitable for survival in the atmospheric environment, and mammals become more advanced and adaptable competitors. Under the influence of these two factors, dinosaurs eventually became extinct. Some remaining reptiles can adapt not only to the old environment, but also to the new environment.
? The theory that the change of atmospheric composition led to the extinction of dinosaurs has two starting points, one is the Mesozoic atmospheric composition, and the other is modern. Modern science has proved this. The other is that every living thing needs a suitable atmospheric environment to survive. Modern science is not difficult to verify this.
? In the ancient atmosphere, there was almost no high content of oxygen and carbon dioxide. Later, due to the appearance of biological photosynthesis, the content of carbon dioxide in the atmosphere gradually decreased and the content of oxygen increased, which can explain many phenomena in the history of biological evolution. For example, the CAMBRIAN Big Bang is a mystery in evolutionary history. The change of atmospheric composition can also be explained, because animals can not directly use inorganic substances for photosynthesis, and its origin is behind the origin of plants, which must occur in a considerable degree of oxygen content in the atmosphere. Therefore, the oxygen content in the atmosphere of the CAMBRIAN Big Bang reached a certain degree of protection, which is scientifically proved.
? The asteroid impact of dinosaur extinction may play a role, but it will not appear is the most critical factor.
In addition to 22 famous sayings, there are many small famous sayings (such as electromagnetic interference caused by sunspots, the direction and changing intensity of the earth's magnetic field), which are the best refutation. Look at everyone's thoughts, there is no certain right or wrong. After all, the mystery of dinosaur extinction has not really been solved!
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Comprehensive cause theory
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Due to the interaction of various internal and external factors, the extinction of dinosaurs is a complicated process, and one of the reasons leading to the extinction of dinosaurs is that it is difficult? The extinction of dinosaurs was caused by many factors.
? But no matter what happens, at least one thing is undeniable. It can't adapt to or change the events of dinosaurs. If they can adapt to or change the environment, will they mysteriously become extinct?
Enlightenment from the extinction of dinosaurs
? Whether these things really happened or not, the extinction of dinosaurs is a strange thing. Fortunately, we now have some rare dinosaur fossils for scientists to study. We hope that this mystery will be solved in the near future. At the same time, we should know that any form of life has to go through the process of emergence, development, prosperity and extinction. This is a natural law and will not change because of the great prosperity of this species. After the extinction of dinosaurs, a new era appeared, the biological world was more advanced and the earth was better decorated.