dinosaur

There are many kinds of dinosaurs, including pterosaurs, Tyrannosaurus Rex and Stegosaurus. What is a dinosaur? A long time ago, there lived a big family on the earth. Their offspring hatch from eggs, and their skin is covered with scales and impervious to water. They rule the sea, land and sky, and all other animals can't compete with them. They are veritable overlords. This is a dinosaur. Dinosaurs ruled the earth for 654.38+0.6 billion years from their appearance to extinction.

Dinosaurs generally lived in three periods in the history of the earth: Triassic, Jurassic and Cretaceous. Different kinds of dinosaurs survived and became extinct in these three periods. Each dinosaur may only live for 2-3 million years. At that time, the climate of the earth was warm and humid, and there were dense forests everywhere. There are all kinds of animals living in the forest. Therefore, no matter whether dinosaurs ate plants or animals, they could not finish eating them. Because of such a good environment, dinosaurs generally grew huge. It is speculated that the largest dinosaur was 30 meters long and weighed more than 50 tons, and now the largest bus can't pull. Of course, there are smaller dinosaurs, such as Palatosaurus, which is only 60 cm long and weighs 3 kg, which is similar to the chicken we see. Dinosaurs usually reproduce in the same way as existing reptiles. China is rich in dinosaur eggs, which is of great significance to the classification of dinosaurs and stratigraphic division and correlation. Dinosaur eggs are often produced in nests, with as many as 20-30 eggs in a nest, overlapping several layers and arranged in concentric circles. The bigger the egg, the closer it is to the center of the circle. Eggs are round and oval in shape, the small diameter is only 50-60 mm, and the big one can reach more than 500 mm. The eggshell is smooth, granular and wrinkled. They represent different dinosaur remains.

But dinosaurs are also doomed to extinction. Tens of millions of years ago, asteroids collided with the earth, triggering a volcanic eruption. Today, we can only see dinosaur fossils.

; ; ;

Chapter II: Dinosaurs

In the Mesozoic era more than 200 million years ago, a large number of reptiles lived on land, so the Mesozoic era was also called the "reptile era", and the earth was widely occupied by vertebrates for the first time. At that time, the earth's climate was warm and there were dense forests everywhere. Reptiles have enough food, and gradually flourish, with more and more kinds. They constantly differentiate into various reptiles, some become turtles today, some become crocodiles today, some become snakes and lizards today, and some evolve into mammals all over the world today.

Dinosaurs are the largest reptiles. They are very suitable for living in swamps and shallow lakes. At that time, the air was warm and humid, and food was easy to find. So dinosaurs ruled the earth for tens of millions of years, but for some reason, they suddenly became extinct in a short time 65 million years ago. Today, people only see a large number of dinosaur fossils left at that time.

People are still studying the reasons for the extinction of dinosaurs. For a long time, the most authoritative view is that the extinction of dinosaurs was related to a big meteorite 65 million years ago. According to research, an asteroid with a diameter of 7- 10 km once fell on the earth's surface, causing a big explosion, throwing a lot of dust into the atmosphere, forming dust fog that covered the sun, leading to the temporary suspension of plant photosynthesis and the extinction of dinosaurs.

The asteroid impact theory quickly gained the support of many scientists. 199 1 year, a meteorite impact crater was discovered in Yucatan Peninsula, Mexico, which further confirmed this view. Today, this view seems to be conclusive.

However, many people are skeptical about this asteroid impact theory, because the fact is that frogs, crocodiles and many other temperature-sensitive animals survived the Cretaceous period. This theory can't explain why only dinosaurs died. So far, scientists have put forward more than a dozen hypotheses about the causes of dinosaur extinction, and the more exciting and dramatic "meteorite impact theory" is just one of them.

In addition to the "meteorite impact theory", the main viewpoints about the extinction of dinosaurs are:

First, the theory of climate change. 65 million years ago, the earth's climate changed suddenly and the temperature plummeted, which led to the decrease of oxygen content in the atmosphere and dinosaurs could not survive. Some people think that dinosaurs were cold-blooded, without hair and warm organs, unable to adapt to the decline of the earth's temperature, and all of them froze to death.

Second, the theory of species struggle. At the end of the dinosaur era, the first small mammals appeared. These animals are rodent carnivores and may feed on dinosaur eggs. Due to the lack of natural enemies, more and more small animals finally ate dinosaur eggs.

Third, the theory of continental drift. Geological research has proved that there was only one continent on the earth when dinosaurs lived, and that was Pangea. Due to the change of the crust, the Jurassic continent split and drifted, which eventually led to the change of environment and climate and the extinction of dinosaurs.

Fourth, the theory of geomagnetic variation. Modern biology has proved that the death of some creatures is related to magnetic fields. When the earth's magnetic field changes, creatures sensitive to the magnetic field may lead to extinction. It can be inferred that the extinction of dinosaurs may be related to the change of the earth's magnetic field.

Five, angiosperm poisoning theory. At the end of the dinosaur era, gymnosperms on the earth gradually became extinct, replaced by a large number of angiosperms, which contained toxins that gymnosperms did not have. Giant dinosaurs ate a lot, and a large number of angiosperms led to excessive accumulation of toxins in the body and finally poisoning.

Sixth, the theory of acid rain. There may have been strong acid rain at the end of Cretaceous, which dissolved trace elements including strontium in the soil. Dinosaurs ingested strontium directly or indirectly through drinking water and food, which led to acute or chronic poisoning and eventually died in batches.

There are many hypotheses about the extinction of dinosaurs. However, these hypotheses have more supporters in the scientific community. Of course, each of the above statements has some imperfections. For example, the "climate change theory" does not clarify the reasons for climate change. After investigation, it was found that some small osteophytes in dinosaurs could compete with early small mammals, so there were loopholes in the theory of species struggle. In modern geology, the "continental drift theory" itself is still a hypothesis. "Angiosperm poisoning theory" and "acid rain theory" also lack sufficient evidence. Therefore, the real reason for the extinction of dinosaurs remains to be further explored.

Article 3: Dinosaurs

Do you know who was the overlord of Jurassic? Let me tell you, that's Tyrannosaurus rex. The following is its information:

Tyrannosaurusrex, also known as Tyrannosaurus Rex, is the only effective species in the model species, or Tyrannosaurus Rex. It is a large carnivorous Tyrannosaurus rex, about 13 meters long and weighing about 7 metric tons. It lived in the last 3 million years of the Maastricht stage at the end of Cretaceous, about 68.5 million to 65.5 million years ago, and was the last dinosaur before the Cretaceous-Tertiary extinction event. Fossils are distributed in North America, the United States and western Canada, and the distribution range is wider than other Tyrannosaurus rex.

It's my favorite dinosaur.

Below is the hadrosaur, which lived in the late Cretaceous 65438+ billion years ago and was the peak of dinosaur development, so it was abundant, accounting for about 75% of herbivorous dinosaurs. They are a large bird-buttock dinosaur. At present (2008), it is found that the maximum length exceeds 2 1 m. Due to the extension and lateral expansion of the maxillary and odontoid bones, the snout of the hadrosaurs formed a wide duckbill-shaped snout, hence the name.

I think it's cute.

Omnivorous dinosaurs, I prefer earthquake dragons. Earthquake dragon means "lizard of earthquake". It was first discovered in 1979, New Mexico, USA, in the late Jurassic. It has been found that the body has a tail; Back; Hips and hind limbs. At first glance, it looks like Liang Long, but the earthquake dragon has a longer tail and a thick pelvis. According to preliminary estimates, its length is at least 35 meters, even more than 40 meters. But now it has shrunk to 32 meters long and weighs 22-27 tons. Zhenlong has a long neck, a small head and a slender tail. The nose grows on the top of the head. Its head and mouth are small, with flat round teeth in front and no teeth in the back. The front legs of zhenlong are shorter than the rear legs. Each foot has five toes, one of which has claws. The earthquake dragon walks on four feet and walks very slowly. They live in groups. Zhenlong is a herbivore. When eating, Zhenlong swallowed all the leaves without chewing. Seismosaurus is one of the largest dinosaurs, but some scientists believe that the dinosaur fossils found belong to an oversized Liang Long. It was once recognized that the longest dinosaur was zhenlong.

The next one is a long-necked dragon living in the sea. Tanystropheus is a reptile that lived in the Middle Triassic, and its length is about 6 meters (20 feet). The main feature is an extremely long neck, which is as long as 3 meters (10 feet), which is longer than the body and tail combined. Although the neck is so long, it has only 12 vertebrae, and each vertebra is quite long. Fossils of long-necked dragons have been found in Europe and the Middle East.

Many complete young specimens of sauropod were found in the Besano Formation in Italy, and the geological age was Latin period of Middle Triassic, about 232 million years ago [1]. The common name of long-necked dragon means "long spine"

This is the end of the introduction. Goodbye.