12 constellation dinosaur distribution area _ 12 constellation dinosaur ranking

What is the status of dinosaurs in nature?

The earth is alive! -Lovelock.

1. After studying ancient rocks, mobile continental geophysicists know that the earth is at least 4.6 billion years old. Long years have made the earth's surface undergo vicissitudes. Scientists have found that the main driving force of these changes comes from the mantle inside the earth-a layer of liquid rock flow under the continental crust, which drives the movement of the solid continental crust floating on it.

In 1960s, geological science experienced a revolution in concept. Traditionally, most geologists mainly analyze the history of the earth from the perspective of vertical movement, and think that the appearance of mountains is the result of the subsidence and bending of the crust. The mountain was denuded and the debris was transported and piled up into a plain; The sea level drops, raising the mainland area; The magma was squeezed and changed the face of the earth. After 1960s, the research and progress of marine geology and paleomagnetism produced a new concept of the earth, and it was recognized that besides vertical movement, large-scale horizontal movement played an important role in the whole evolution of the earth. This is the geological science (12) that today's continent is composed of many landmasses, which is called "plate theory". Collisions between plates can cause earthquakes; The movement caused the accumulation of strata and the formation of mountains.

Jurassic red rocks containing dinosaur fossils in Turpan basin. The rocks are stacked layer by layer, and the layers spread in the east-west direction. The red rock formation is like a burning flame in the setting sun. This is the "Flame Mountain" in the famous The Journey to the West.

If you are interested, you can find a globe and take a closer look at the shapes of the continents. The edges of some continents can be spliced together, such as the northeast corner of South America and the Golden Bay of Africa, and the east edge of North America and the west coast of Europe can be spliced into a whole. The continents on the earth were originally a whole more than 200 million years ago, which geologists called Pangea, also known as Pangea.

Moving continent-the process of continental drift

230 million years ago (late Triassic), dinosaurs appeared on Pangea. Because there is no vast ocean barrier, Triassic dinosaurs are distributed all over the world, and dinosaurs found on all continents look very similar. At the end of Triassic, Pangu began to split into two continents, one called Gondwana ancient continent in the south and the other called Lauya continent in the north. Gondwana is the name of an ancient tribe in central India. Austrian geologist Ai Du de? Theseus borrowed it to call the southern hemisphere continent. Therefore, this can satisfactorily explain why Australia, Africa, Antarctica and the Indian Peninsula are so similar in many aspects such as ancient glaciers, rocks and paleontology in sediments more than 200 million years ago.

During the Jurassic period (about 65438+600 million years ago), the northern continent (Lauya continent) and Gondwana continent drifted gradually, but they did not drift completely. Some molecules in dinosaur fauna are still related, such as the discovery of giant brachiosaurus in East Africa and North America. By the early Cretaceous/kloc-0.2 billion years ago, the cracks between continents were widening, the Atlantic began to widen from east to west, and Antarctica and Australia drifted away from South America and Africa. By the end of Cretaceous, India drifted from south to north and collided with the southern tip of the Asian continent. The huge collision and compression caused the edges of India and ancient Asia to uplift, and gradually formed the Himalayas, which is the roof of the world today. By the end of the dinosaur era, the mainland had moved to its present position. Nowadays, the zonal distribution of earthquakes and volcanoes and their frequent occurrence prove that the mainland is still moving and squeezing.

2. History of the Earth

People often ask the question: When did dinosaurs live? Did our human ancestors ever see dinosaurs? Of course, some people think it is difficult to understand that there are grotesque dinosaurs on the earth. In fact, dinosaurs are the product of natural history, and they have a unique position in the time and space of nature. So it is necessary to find out the age of dinosaurs. But to understand this problem, we must start from the history of the earth. Living on the earth, we always want to know the past of the earth. In order to use its resources and protect its environment, we also need to know its age.

How to determine the age of the earth? People have come up with many ways to guess the age of the earth. At present, the commonly used paleontological method is to determine the age of the earth by comparing fossils. The principle of this method is very simple, that is, according to the principle of biological evolution. Biology always develops in two ways, from simple to complex, from low to high. Different geological ages have different biota. When organisms are buried and turned into fossils after death, generally, low-grade fossils are in an older age, while high-grade fossils are in a newer age. In this way, the relative order of the development history of the earth can be established according to fossils in different geological periods. But the earth history established by this method can only be a relative sequence in time, and can't tell the quantitative figures of many years ago. Moreover, fossils appeared in the late stage of the earth's history, and some rocks (such as granite) formed by deep magmatism in the earth's crust do not contain fossils, so it is impossible to determine their geological age by fossil method. In recent years, through the efforts of many scientists, a "clock" for measuring geological time, that is, radioactive isotopes, has been discovered. All the elements that make up a substance have different amounts of isotopes, including stable isotopes and radioactive isotopes. Radioisotopes are not affected by external temperature and pressure when they change (decay). They decay constantly, and the time required to reduce them to half is called "half-life". Minerals and rocks in the earth's crust contain radioactive elements from the time they are formed, and decay according to the law of decay, from parent isotopes to daughter isotopes. If we know its half-life and determine the number of parent isotopes and daughter isotopes, we can calculate the geological age of minerals or rocks. The age determined in this way is called "absolute age".

According to the determination of radioactive isotopes, the earth is at least 4.6 billion years old. In addition, according to the discovered fossils and crustal movement, scientists divide the history of the earth into Archean, Proterozoic and Phanerozoic. Under Zhou, it can be divided into several generations. Archean is divided into Archean, Archean, Middle Archean and NeoArchean, Proterozoic is divided into Proterozoic, Mesoproterozoic and Neoproterozoic, and Phanerozoic is divided into Paleozoic, Mesozoic and Cenozoic. Instead, it can be divided into several periods, instead, it can be divided into several periods. Dinosaurs lived in three periods of Mesozoic-Triassic, Jurassic and Cretaceous.

In order to find out the ins and outs of dinosaurs, let's briefly review the evolutionary history of biology.

The beginning of biological evolution is a gestation and germination stage of primitive life. At present, the earliest known biological fossil in the world is the 3.2 billion-year-old Bacillus fossil found in South Africa. It is a prokaryote without a nucleus. By 654.38+0.8 billion ~ 654.38+0.3 billion years ago, nucleated eukaryotes, namely blue-green algae fossils, appeared. /kloc-From 0/100 million to 542 million years ago, in the Neoproterozoic, in addition to unicellular blue-green algae, multicellular filaments appeared, which was a leap in biological development.

By the early Cambrian of Paleozoic 542 million years ago, higher invertebrates had appeared in addition to lower invertebrates such as bacteria, algae, sponges and brachiopods, and trilobites were the most invertebrates in this period. The spark of life in the past has already started a prairie fire and the living things have exploded. More than 500 million years ago, the earliest vertebrate-jaw appeared. The jawless class is a fish-shaped animal. In the early Silurian 440 million years ago, the earliest jaw fish appeared. It is generally believed that primitive fish evolved into two branches, namely cartilaginous fish and bony fish. During the heyday of Devonian 400 million years ago, Devonian was called "the age of fish". At the same time, a large number of primitive terrestrial plants-naked ferns have appeared on the lakeshore and seaside, which makes mountains and deserts wear green clothes for the first time, which is a leap from aquatic to terrestrial.

The history of the earth is developing, and the huge flow of biological evolution is slowly advancing. In the late Devonian, 350 million years ago, amphibians differentiated from primitive teleost fish appeared. Its appearance has opened up a vast world for vertebrates to further conquer land.

In the Late Paleozoic-Carboniferous and Permian, the climate of the whole earth was hot and humid, and the descendants of gymnosperms-arthropods, true ferns, lycopodium and so on. Has been fully developed. For example, the scales of lycopodium can be as high as 40 meters, forming a huge tree. The vast continent is full of lush virgin forests. However, at this time, there are neither birds nor flowers, and the earth looks monotonous and quiet. Only some slow-moving amphibians wander in the swamp of the jungle, and occasionally large dragonflies with a body length of about 1 m can be seen flying at low altitude. In the Carboniferous, the evolution of vertebrates underwent a major qualitative change, and reptiles appeared. Reptiles lay eggs directly on land, completely getting rid of the dependence on water, making vertebrates complete the leap from aquatic to terrestrial. However, the great development of reptiles occupied all fields of land, sea and air, and became the master of the earth, which was still in the Mesozoic era.

Compared with Paleozoic, the earth landscape of Mesozoic is very different. The most prominent change in plants is that gymnosperms, such as Cycas, Ginkgo biloba and conifers, have replaced the position of late Paleozoic pteridophytes (plants that reproduce with seeds are called seed plants, gymnosperms whose seeds are not covered by pericarp, and angiosperms whose seeds are covered by pericarp). The most prominent change in the animal kingdom is that reptiles have reached their peak and become rulers. There are dinosaurs on the land, ichthyosaurs, plesiosaurs, magic dragon and black dragon in the water, and pterosaurs in the air. So people call the Mesozoic "the age of dragons". In the late Triassic, mammals evolved from primitive reptiles appeared. In the late Jurassic, archaeopteryx, a transitional type of birds evolved from reptiles, also appeared. At the end of Mesozoic, drastic environmental changes took place on the earth, and many reptiles could not adapt to this change. Many reptiles, including dinosaurs, were extinct, but the newborn mammals withstood the severe test of this great change and laid the foundation for the great development of a new generation.

The history of life on earth

The natural environment and biological features of the Cenozoic era are basically similar to those of modern times. Angiosperms have made great progress, and mammals have reached unprecedented prosperity, especially in the late Cenozoic. Human activities have changed the earth, so the history of the earth has turned a new page.

As can be seen from the above description, dinosaurs developed after a long period of gestation, which is the product of the development of the earth and biological evolution. We humans appeared on the earth more than 60 million years after the extinction of dinosaurs, and even our ancestors could not have seen dinosaurs. Some people think that "Beijingers" who live in Zhoukoudian, Beijing, once struggled with dinosaurs, which is a misunderstanding caused by not knowing the survival time of dinosaurs and the history of the earth.

3. The position of dinosaurs in the animal kingdom

We already know that dinosaurs were extinct vertebrates that lived in Mesozoic era, and they were closely related to other reptiles. So, what is the status of dinosaurs in the animal kingdom, especially in reptiles? What does it have to do with other reptiles?

From the smallest single-celled protozoa that can only be seen under a microscope to the largest cetaceans, they are all members of the animal kingdom. Although they vary in size, they can be divided into invertebrates and vertebrates according to anatomical characteristics, especially according to whether there is a spine (that is, spine) composed of multiple vertebrae in the body. There are many kinds of invertebrates, ranging from the most primitive protozoa (such as plasmodium, amoebic dysentery and paramecium) to higher arthropods (such as shrimps, crabs, insects, spiders and trilobites) and echinoderms (such as starfish and sea cucumbers).

As mentioned above, the lowest vertebrate is jawless, which evolved from jawless to shield fish with jaws, from fish to amphibians, and then from amphibians to complete terrestrial reptiles. Modern turtles, snakes, crocodiles and lizards are all "descendants" left by ancient reptiles, and dinosaurs have many similarities with these four remaining reptiles. Dinosaur bones, especially skulls, are similar to crocodiles in structure, with a pair of temporal holes at the back of the head. Their teeth are implanted in a similar way, and they have more slots; Some of them are covered with scaly bone plates. These characteristics tell us that dinosaurs and crocodiles are closely related, and both belong to Ampodactyla.

In order to deeply understand the living habits of dinosaurs, let's briefly introduce the main characteristics of reptiles. When it comes to reptiles, people immediately think of familiar snakes. Many people know an old fable: a poisonous snake froze to death on the side of the road. When a kind farmer saw it, he felt sorry for it and put it on his chest. When the snake woke up, it recovered its nature and killed its benefactor in one bite. This story warns us not to pity the wicked like poisonous snakes, and also tells us a common sense: snakes are afraid of cold, and their body temperature changes with the temperature of the external environment. This animal is called "warm-blooded" or "cold-blooded". The existing reptiles are all warm (cold-blooded) animals. Mammals are very different. Their body temperature is constant. If the adult's body temperature exceeds 37 degrees Celsius, it is generally a fever. Mammals' body temperature is not affected by the external environment temperature, and they can adjust their body temperature. This kind of animal is called "warm-blooded" or "warm-blooded". Modern reptiles can only live in tropics, subtropics and temperate zones because of their unstable body temperature. The farther away from the poles of the earth, the fewer kinds and numbers of reptiles there are. Because the polar climate is cold, they can't find an effective way to keep warm and will soon freeze to death. Still taking the snake as an example, when the outside temperature drops to 10 degrees Celsius, its action is not very flexible; When the temperature drops to 3 degrees Celsius to 2 degrees Celsius, general paralysis may occur; It will die when its body temperature drops to MINUS 4 degrees Celsius to MINUS 6 degrees Celsius. Similarly, if the weather is too hot, they must hide in the shade, crevices in rocks or other places in summer, otherwise they will die because they can't stand the high temperature. Generally speaking, reptiles can only tolerate the "high temperature" of 38 degrees Celsius. Because they are far less tolerant to temperature than mammals, their geographical distribution is limited. About the temperature of dinosaurs, there is still a dispute between warm blood and cold blood.

Why can't reptiles regulate their body temperature? Mainly because their circulatory system is not fully developed. The heart of a reptile has two atria and one ventricle. Although ventricles tend to distinguish between left and right ventricles, they are not completely separated, and arterial blood and venous blood in ventricles are mixed. They have no temperature control function in their bodies and no warm fur outside their bodies. Reptiles are naked, covered with decks or scales, and there is no fat layer under the skin like mammals.

Reptiles breed by laying eggs directly on land and then incubating their offspring. An egg not only has a thick eggshell, but also has an amniotic membrane that nourishes, protects the fetus and prevents dryness. We call it "chorionic egg", so it doesn't need to undergo metamorphosis like amphibians (hatching larvae in water), so reptiles are land animals that really leave water. Some special groups, such as lizards, hatch eggs in the body cavity of the mother and produce small animals. This way of reproduction is also different from viviparous in mammals, because they have no placenta and do not absorb the nutrition of the mother, so they are called "viviparous", and ichthyosaurs are viviparous.

Another characteristic of reptiles is that they grow all their lives, that is, they grow all their lives, while the growth of mammals stops at a certain stage. For this reason, although turtle eggs, snake eggs and crocodile eggs are small, they can grow into big bodies after breaking their shells. Dinosaurs are also oviparous, which has been proved by the small dinosaur skeleton fossils preserved in the egg fossils found. So dinosaur eggs are small, but they can grow into big dinosaurs.

Dinosaur bones are like living reptiles. Reptiles are often classified according to the structure of the skull, that is, whether there are "temporal holes" on the skull and the location and number of holes. Temporal foramen refers to the foramen located on the side of reptile skull and behind the eyes. It is generally believed that temporal foramen has two functions: one is to reduce the weight of skull; The other is that when the strong temporomandibular muscles of the upper and lower jaws contract, the muscles on the skull contract more strongly. Especially those meat eaters have the most developed caves. This is the result of reptiles adapting to land life. Amphibians have no temporal foramen. According to this temporal foramen, biologists divide reptiles into four categories.

The first category: foraminifera without temporal foramen. It is an ancient reptile, and the turtles that are still alive today belong to this category. This is a primitive feature of evolution.

Nonporous class

The second type: the skull has only a pair of temporal holes, but the position of the holes is low, which is located below the scales and retroorbital bone at the outer edge of the ear fossa, and is called the inferior hole. Among ancient reptiles, this kind of animals is very similar to mammals in structure, and people call it "mammal-like reptiles".

Lower pore grade

The third type: there is a pair of temporal foramen, located on the upper side, above the scalene bone and the retroorbital bone, called the adjustable foramen skull. Magic dragon and plesiosaur all belong to this type. In recent years, researchers believe that the skull with adjustable hole is changed from the double-hole type without the lateral temporal hole, so magic dragon is classified as the double-hole type.

Hole-adjusting class

The fourth type: there are two temporal holes on both sides of the skull, which are located above and below the scalene bone and the retroorbital bone, respectively, called double holes. This is the most diverse group. Snakes, lizards, crocodiles, pterosaurs and dinosaurs all belong to this category.

Double pore class