Some knowledge of dinosaurs
since ancient times, there have been many different opinions about the real reason for the extinction of dinosaurs, but there is no certain argument, so it is still an unsolved puzzle. Here, only some well-known statements are described as follows:
1. Meteorite collision theory:
65 million years ago, a huge meteorite hit the earth, making the dinosaurs extinct for hundreds of millions of years. This theory was put forward by four scientists, including Dr. Louis Albales of the University of California, Berkeley.
This huge meteorite is about ten kilometers in diameter. The crater topography caused by the impact is 2 kilometers in diameter. The energy generated by the impact, if converted into yellow powder, is equivalent to one million tons (megaton). Dust diffuses into the stratified circle through the atmosphere. It led to the darkness of the earth for several months. During this period, many creatures, led by dinosaurs, became extinct.
2. The theory of comet collision:
The theory of comet collision began with the argument that the extinction of paleontology occurs once every 26 million years published by paleontologists David Laup and John Sepkowski. Louis Albalez gave this argument and his own theory to the astrophysicist-Charlie Murat, and later Murat thought that the comet was periodically pushed to the earth because of the gravity of the sun's nemesis.
Third, the orogeny said:
The orogeny at the end of Cretaceous dried up the swamp, and many dinosaurs who lived in the swamp could no longer live. Because of the post-qi change, 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 for 1-2 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 a huge climate change. The cold climate killed plants, and dinosaurs died because of lack of food.
5. Volcano spits fire:
Because of the eruption of volcano, a large amount of carbon dioxide is spewed out, which causes the greenhouse effect of the earth and causes food death. Moreover, the volcano spewed fire, which caused a large amount of salt to be released, the ozone layer was broken, and harmful ultraviolet rays irradiated the earth's surface, causing biological extinction.
VI. Ocean ebb theory:
According to Barker, when the ocean ebbs, when the land borders, creatures touch each other, thus causing certain species of creatures to become extinct. Kangaroos, for example, can live on the island continent of Europe, but they will die when they meet other animals on the South American continent.
In addition to this relationship between eating and being eaten, there are also infectious problems such as diseases and parasites.
7. Warm-blooded animals say:
Some people think that dinosaurs were warm-blooded animals, so they could not stand the cold weather in the late Cretaceous and could not survive. Because even if dinosaurs are warm-blooded, their body temperature is still not high, which may be similar to that of living sloths, and to maintain such a body temperature, they can only live in tropical climates. At the same time, the respiratory organs of dinosaurs were not perfect, and they could not fully replenish oxygen. They did not have thick hair to avoid body temperature loss, but they easily lost 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 enter the cave to avoid the cold, so if the cold days last for a few days, they may be frozen to death because of exhaustion of physical strength.
Eight. The theory of cannibalism:
Some people think that the real reason for the extinction of dinosaurs is the result of their cannibalism-carnivorous dinosaurs ate herbivorous dinosaurs, while 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 ended up mutually assured destruction.
9. Oppression theory:
The number of dinosaurs increased rapidly, which led to the extinction of herbivorous dinosaurs under the condition of limited plants, and then carnivorous dinosaurs who lived on herbivorous dinosaurs died because of lack of food. (Doubt: Why did dinosaurs suddenly increase after about 2 million years of ecological balance? The important key to the establishment of this theory has also directly caused many scholars to review the reasons for the abnormal increase in dinosaur production. )
1. Mammalian prisoners said:
In the second half of Mesozoic, ancestors of mammals existed. According to the records of fossils, the 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 omnivorous with insects as their staple food. After discovering dinosaur eggs, these small mammals kept eating them.
(My opinion: Is this really the case? If mammals beat dinosaurs, then with the increase of mammalian fossils, dinosaur fossils should be gradually reduced, but in fact there is no such phenomenon of fossil alternation. In other books, the real increase of mammalian fossils was after the end of the dinosaur era. Moreover, dinosaur fossils disappeared suddenly. Therefore, the theory that dinosaurs were wiped out by mammals cannot be established. )
11. The aging theory of species:
It is believed that dinosaurs' bodies were too large because of their prosperity for hundreds of millions of years. Moreover, horns and other bones are also extremely developed, which causes great inconvenience in life and finally leads to extinction.
Lei Long, the most representative dinosaur, was 25 meters long and weighed 3 tons. Because of his huge size, he was slow to move and lost his ability to live. In addition, Triceratops and others went to the road of self-destruction because of the ever-increasing three horns and the 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 whose bones are like deer and can run briskly. But why did this dinosaur become extinct at the same time? Moreover, in cold-blooded animals, abnormally developed bones and other parts are supposed to be able to absorb the outside temperature and release the heat in the body to adjust the body temperature, which has a very favorable function. Therefore, I doubt that dinosaurs became extinct because of the aging of species. )
12. Alkaloid theory:
This theory holds that flowering plants began to appear in the last period of dinosaurs' existence, that is, the Cretaceous period, and some of them contained toxic alkaloids. Dinosaurs died of poisoning due to large intake. Because mammals can distinguish poisonous plants by taste and smell, but dinosaurs have no such ability.
However, plants containing alkaloids did not suddenly appear in the late Cretaceous, and they were already seen five million years before dinosaurs became extinct. This theory does not explain why dinosaurs survived during this period.
In addition to the above twelve statements, there are other lesser-known statements, such as "infectious diseases", "explosion of radiation or supernovae from the universe", "not taking Noah's Ark" and "solar system vibration". As for which one is the best statement, it depends on everyone's ideas, and there is no certain right or wrong. After all, the mystery of dinosaur extinction has not really been solved!
The oldest reptile fossils can be traced back to the Paleozoic Pennsylvanian (31 million years ago-275 million years ago). Tracing back to the source, it was evolved from amphibians. Amphibian eggs need to develop in water. Reptiles have evolved egg shells to prevent water from escaping. This major reform has enabled reptiles to live without water.
from 225 million years ago to 65 million years ago, reptiles became the dominator on the earth, so the Mesozoic era was also called the reptilian era. Large reptilian dinosaurs appeared in the early Mesozoic. Herbivorous Liang Long and Lei Long are the largest terrestrial animals. Tyrannosaurus rex is a carnivorous dinosaur. There are also ichthyosaurs living in the sea and pterosaurs living in the air.
reptiles have flourished on the earth for about 15 million years. Among the animals of this era, dinosaurs are the most well-known ones. When people mention dinosaurs, they will see a huge and fierce animal. In fact, there are also small and tame dinosaurs among dinosaurs.
dinosaurs belong to vertebrate reptiles, which were once found in Mesozoic land swamps, with a long neck and tail. The hindlimb is longer than the forelimb and has a tail. Among them, several species are carnivorous and several species are herbivorous, which are huge and can be considered as the largest terrestrial animals. Its physique in the lower species, there are like the oldest crocodiles and beaks, in the higher species slightly similar to birds.
the study of dinosaurs depends entirely on fossils. Paleontologists infer their morphology and habits from their fossils. According to paleontologists, dinosaurs are like living animals: there are big ones and small ones; Some walk on two legs; Some walk on four legs; Some eat plants, some eat animals; Some skin is smooth, and some skin has scales or bone plates. Its similarity is that all dinosaurs have small brains and lay eggs on land (as do all reptiles).
(1) Lei Long:
Some dinosaurs have huge bodies, such as Lei Long. During the Jurassic period, the climate on the earth was warm and humid, and there were lush forests everywhere. Because of these rich plant foods, herbivorous dinosaurs flourished. After that, Lei Long was also active in the plains of North America.
Lei Long weighs about 35 to 5 metric tons, and its stout legs are like tree trunks. A long neck, standing as high as a seven-story building, can be said to be the largest animal in the world. Although Lei Long's body is surprisingly large, her temperament is very gentle. She usually feeds on plants in temperate forests and sometimes walks into swamps. Because of the buoyancy of water, she can reduce the heavy burden on her body and avoid the attack of a carnivorous dinosaur as fierce as Allosaurus.
(2) Three Chironosaurus:
Bone plates and fragments on Stegosaurus and Ceratosaurus can only be used for passive defense, but there is no way to fight back. It was only when Chironosaurus appeared that the situation gradually changed. Sansaurus is the largest of all sauropods, with two spear-like horns on its head and the other horn protruding between its eyes and nostrils. Such a sharp weapon, even the most terrible carnivorous dinosaur will make it three points.
(3) Stegosaurus:
Stegosaurus, which appeared 15 million years ago, is characterized by two ribs on its back and sharp spines on its tail. Stegosaurus was a herbivorous dinosaur, and it moved slowly. Its bone plate and sharp spines on its tail became the best defense against carnivorous dinosaurs.
(4) Ankylosaurus:
Stegosaurus was protected by a bone plate, but it was still vulnerable where the bone plate could not cover it. When stegosaurus gradually disappeared, Ankylosaurus (Armadillosaurus) covered with bone plates took its place. Ankylosaurus is like an invulnerable tank car, and even Tyrannosaurus Rex can't help it.
(5) Tyrannosaurus Rex:
Tyrannosaurus Rex (Tyrannosaurus Rex) is the largest and most brutal carnivorous dinosaur. Tyrannosaurus Rex appeared at the last stage of the dinosaur era, about 8 million years ago. Tyrannosaurus rex's body is 14 meters high and weighs about 1 metric tons. Its hind feet are so thick and strong that it can even support a rhinoceros.
From the fossils of Tyrannosaurus Rex, it is found that every tooth is as big as an adult's palm, and even its eyes are bigger than a human head. Although most of the body is surprisingly large, the forelimbs of Tyrannosaurus rex are so small and short that it is impossible to send food into the mouth. The killer dragon has the same habits as Tyrannosaurus rex and is a fierce animal.
[6] Archaeosaurus:
Like Tyrannosaurus Rex, Archaeosaurus appeared at the end of the dinosaur era. The most special thing about the duck-crested dragon is its head. Its flat and long jawbone looks like a duck's mouth, so it has the name of the duck-crested dragon. In the past, people thought that the life of the duck-crowned dragon was similar to that of a duck. It swam in the water and lived on plants in the water. Later, when scientists studied the fossils of the duck-crested dragon, they found that they did not eat aquatic plants for a living, but lived on trees on the shore, and the goose-crested dragon had the same habit.
Who first discovered dinosaurs
Mr. and Mrs. Mantels
There is a small place called Lewis in Sussex, in the south of England. 18 years ago, there lived a village doctor named Mantel. This Mr Mantel is full of curiosity about nature, and especially likes collecting and studying fossils. In addition to practicing medicine and treating diseases, he often takes his wife climbing mountains and wading together to find and collect fossils, and his footprints have traveled all over the gullies and ridges with rock formations exposed around him. Over time, Mrs Mantell has also become a "friend of nature" and a master of fossil collection.
Iguanodon
One day in March p>1822, the weather was very cold, but Mr. Mantel went out to see the patient as usual. The lady is waiting for her husband to come back at home, and she is always worried about whether he will catch cold. Later, Mrs Mantell couldn't sit still, so she took her husband's clothes and went out to meet him in the direction of his house calls. She was walking on a road under construction, and the newly cut steep walls on both sides of the road exposed layers of rocks. She habitually walked and observed the newly exposed rock formations on both sides. Suddenly, something shiny caught her attention. "What is this?" As she talked to herself, she stepped forward to watch carefully. Wow! It turned out to be some strange-looking animal tooth fossils. These fossil teeth are so big that Mrs Mantell has never seen such big teeth. The excitement of discovery made Mrs. Mantell forget about sending clothes to her husband. She carefully took these fossils out of the rocks and brought them home.
later, Mr mantel returned home. He was shocked when his wife presented the newly collected fossils to him. He has seen many fossil teeth of ancient animals, but none of them can be similar to such large and strange teeth.
Not long after, Mr. Mantel found many such tooth fossils and related bone fossils near the place where the fossils were found. In order to find out what animals these fossils belong to, Mr Mantell took them to Ju Weiye, a French naturalist, and asked the most famous scholar in the world at that time to identify them.
To tell the truth, Ju Weiye has never seen such fossils, and all the books and papers written by senior scientists he has read have never mentioned such fossils. However, Ju Weiye made a judgment based on his rich knowledge of zoology. He thought that the teeth belonged to rhinoceros and the bones belonged to hippopotamus, and their ages were not too old.
Mr mantel is very skeptical about Ju Weiye's appraisal. He thinks Ju Weiye's conclusion is too hasty. He decided to continue his research. From then on, whenever he had the chance, he went to museums around the country to compare specimens and consult data.