Jurassic (about 208 million years ago ~ 654.38+440 million years ago) (era of reptiles and gymnosperms)

brief introduction

It belongs to the middle Mesozoic. The second period of Mesozoic. The stratum formed in this period is called Jurassic, which is located above Permian and below Cretaceous. Pangea, a super land mass, really began to split at this time. Cracks in the continental crust form the Atlantic Ocean. Africa began to split from South America, while India was ready to move to Asia.

Some important events in the history of biological development have attracted people's attention. For example, dinosaurs became the rulers of land, pterosaurs and birds appeared, and mammals began to develop. Terrestrial gymnosperms have reached their peak. The bivalves, gastropods, arachnids, ostracods and insects of freshwater invertebrates have developed rapidly. Marine ammonites, bivalves and arrow stones are still important members, and the six-coral has not changed much from Triassic to Jurassic. Echinoderm sea urchin has occupied an important position since Jurassic.

Reptiles developed rapidly in Jurassic. The lazy tooth is extinct, and so is the ocean magic dragon. The evolutionary type of dinosaurs-two of the four main bird hips flourished in Jurassic, and flying reptiles glided in the sky for the first time. The first appearance of birds is one of the important changes in the history of animal development. Another kind of dinosaur, sauropod dinosaur, flourished in the Jurassic period: one was a carnivorous dinosaur, and the other was a huge herbivorous dinosaur. Marine reptiles, mainly ichthyosaurs and plesiosaurs, have become members of the marine environment that cannot be ignored.

Some of the most primitive mammals that appeared in the late Triassic were on the verge of extinction in the late Jurassic. In the early Jurassic, other early types of mammals, Polyodon, were newly produced, which were considered to be herbivorous and extinct in the early Cenozoic. Ancient mammals that appeared in the Middle Jurassic are generally considered as the ancestors of marsupials and placental mammals.

Cartilaginous scleroderma began to decline in Jurassic and was replaced by whole bone fish. The earliest true bone fish discovered in Triassic developed greatly in the late Jurassic, and the number increased, but the species was less.

In Jurassic, there were many evolutions of ammonites, which were mainly manifested in the complex suture lines, diversified shell ornamentation and shell shapes, which may be caused by ammonites adapting to different marine environments and various lifestyles. The Jurassic marine bivalves were abundant, and the non-marine bivalves also developed rapidly, which played an important role in the division and correlation of continental strata.

Jurassic is the heyday of gymnosperms. The development of cycads and ginkgo reached a peak, and conifers also occupied a very important position.

source

The name of Jurassic originated from Jura Mountain (now translated as Jura Mountain) on the border between Switzerland and France, and was put forward by French paleontologist A. Browniar in 1829. Because the lithology of Jurassic in Europe is obviously divided into three parts, 1837, L.von Buch divided the Jurassic in southern Germany into three parts: lower, middle and upper. 1843, F.A. Kunsted called the lower black marl black Jurassic, the middle brown iron-bearing limestone brown Jurassic, and the upper white marl white Jurassic. The Jurassic can be divided into three periods: early, middle and late.

floor

The marine Jurassic strata are rich in fossils, especially ammonites, which have obvious characteristics and are well preserved. On this basis, in 18 15, W. Smith of Britain put forward the idea of using paleontological fossils to divide and correlate strata. 1842, French A.C. Daubigny proposed the chronostratigraphic unit order smaller than this series, and named most of the orders Jurassic. In 1856, German A. hooper proposed a more detailed division of the ammonite belt. Jurassic strata are officially divided into three series, 1 1 step, and 74 ammonite belt. The Lower Jurassic (rias) is divided into Hutang Stage, Sinnemuer Stage, Prinsbach Stage and Thor Stage. The Middle Jurassic (Doug System) is divided into Alin Stage, Balu Stage, Batumian Stage and Kaluonian Stage. The Upper Jurassic (Ma Meng) is divided into Oxford Stage, Kimberlite Stage, Tethyan Stage (Volga Stage) and beria Stage. The detailed zoning of ammonites provides a good foundation for the division and correlation of marine Jurassic in the world. At present, the international division of the top boundary and series of marine Jurassic has not been unified. The Jurassic strata in China are dominated by continental deposits. Because the evolution speed and distribution breadth of terrestrial organisms are not as fast as ammonites, the research accuracy of terrestrial Jurassic is relatively low.

Geological and biological events

There are some obvious geological and biological events in Jurassic. The largest transgression occurred in the Kimberly period of the late Jurassic, which was consistent with the event of joint continental division and the increase of new ocean expansion rate. The Nevada movement in the Pacific Rim also occurred during the Kimberly period, which may indicate that there is some connection between the intensified division of the United ancient land and the accelerated subduction of the ancient Pacific plate. Since the late Kimberly period, there has been an obvious separation of marine animals between the Tethys region and the northern region, reflecting the strengthening of paleoclimate zoning and paleogeographic isolation. The cooling events at the end of the Middle Jurassic were reflected in many places in Eurasia. In recent years, rare anomalies of iridium and osmium have been found in the boundary layer of Middle-Upper Jurassic in Poland and Spain. Some people think that this is the result of small extraterrestrial stars hitting the earth.

Paleoclimate and minerals

At this time, the weather around the world is very warm, and the seawater flowing into the cracks produces humid winds, and the inland desert brings rainfall. Plants extended to previously barren areas to provide food for dinosaurs (including the largest land animals) which were widely distributed and numerous. The earliest birds flew over them; These birds may have evolved from small dinosaurs. The ocean is shared by large swimming new reptiles and bony fish with [modern] lines.

The climate is warmer and more uniform than modern times, but there are also differences among tropical, subtropical and temperate zones. In the early and middle Jurassic, the arid climate zone represented by evaporite and aeolian sand dunes appeared in North America, South America and southern Africa, which combined the central and western parts of the ancient land, and extended to central and southern Asia in the late Jurassic. South China was in a tropical-subtropical humid climate in the early Jurassic, and gradually became a dry-hot environment in the middle and late Jurassic. The climate in northern China was warm and humid in the early and middle Jurassic, and the warm and humid area decreased in the late Jurassic. The strong tectonic changes around the Pacific Ocean are closely related to the subduction of the Pacific plate to the surrounding continental plates. With the strong tectonic movement and magmatic activity, minerals such as tungsten, tin, molybdenum, lead, zinc, copper and iron were formed, which became the main part of the Pacific metal metallogenic belt.

Life on land

The main herbivorous vertebrates are protosauropods and pterosaurs, as well as small reptiles similar to mammals. But in the later period, the giant dragon-footed dinosaurs dominated. These animals can eat both higher plants and lower plants; Dragon feet grind food mainly by swallowing stones.

Large theropod dinosaurs preyed on herbivores; However, small theropods, such as bonobos and Micrognathus, preyed on small prey and may also feed on carrion.

Creatures in the air

Pterosaurs with leather wings are the dominant creatures in the air. Early birds also appeared, the most famous being primitive birds. Their bones, teeth and claws were similar to those of small theropods dinosaurs, but they also had long bones. Feather wings and tail, can fly.

Jurassic —— Dinosaur Age

Jurassic is the heyday of dinosaurs, and the dinosaurs that appeared and began to develop in Triassic have quickly become the rulers of the earth. All kinds of dinosaurs came together to form a world of dragons with different shapes. At that time, besides Lei Long and Liang Long having huge bodies on land, ichthyosaurs and pterosaurs flying in the water also had great development and evolution.

bird

The appearance of birds represents another important event in the evolution of vertebrates. 186 1 the archaeopteryx fossil found in the late Jurassic strata in Sorenhofen, Bavaria, Germany, is recognized as the oldest representative of birds. In recent years, the fossil "Sinosauropteryx" discovered by paleontologists in China in Liaoning Province has attracted extensive attention from international academic circles, providing new important data for studying the origin of feathers and the origin and evolution of birds. With the appearance of birds, vertebrates occupied the three ecological fields of land, sea and air for the first time.

insect

The Jurassic insects were more diverse, with about 1000 species living near forests, lakes and swamps. Besides cockroaches, dragonflies and beetles, there are grubs, tree lice, flies and moths. Most of these insects still exist in modern times.

plant

Coniferous forest is a close relative of Chilean pine, which stands out among the big forests composed of tree fern, cycad palmatum and cycad. The ground is covered with dense plants composed of ferns and equisetum.

In the Jurassic plant community, gymnosperms include Cycas, conifers and Ginkgo biloba. Extremely prosperous Equisetum equisetum, true fern and dense pine, cypress, ginkgo and tree fern form a lush forest, while herbaceous ferns and other grasses cover the whole lower ground. Cycas and ferns grow in relatively dry areas, forming a large evergreen Yuan Ye. Before Jurassic, the flora division on the earth was obvious. Due to migration and evolution, the appearance of Jurassic flora tends to be similar in all regions of the earth, indicating that the climate of Jurassic is generally similar.

Creatures in water

Pseudosaurus and hadrosaurs were extinct, but ichthyosaurs survived. Animals living in shallow water also include a group of sea crocodiles and bony fish whose limbs have evolved into flippers. Other marine life includes plesiosaurs and short dragons. In the later period, ichthyosaurs and sea crocodiles gradually declined.

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Dinosaur information:

Dinosaurs are Mesozoic reptiles, which appeared 245 million years ago and flourished 65 million years ago. Or both dinosaurs and plesiosaurs and pterosaurs. Dinosaurs suddenly disappeared in a certain period, which became a mystery in the evolution history of life on earth, and no one has solved it so far. In the past, all living things on the earth were recorded in fossils. Many dinosaur fossils have been found in Mesozoic strata. A large number of bones or various shapes can be seen in it. However, in the subsequent Cenozoic strata, there were no dinosaur fossils at all. It can be inferred that dinosaurs died out together in Mesozoic.

There are many kinds of dinosaurs, and their shapes and habits are quite different. Among them, the big one can be as big as dozens of elephants combined; Small, but almost like a chicken. As far as food habits are concerned, dinosaurs have mild vegetarians and fierce carnivores, and there are omnivorous dinosaurs that eat both vegetarian and vegetarian foods.

The real reason for the extinction of dinosaurs has been debated since ancient times, but there is no definite statement, so it is still an unsolved mystery. Here are only some well-known statements as follows:

1. meteorite collision theory:

65 million years ago, a huge meteorite hit the earth, making the dinosaurs that lived in King's Landing 1 100 million years extinct. This theory was put forward by four scientists, including Dr. Luis Albales of the University of California, Berkeley.

This huge meteorite is about ten kilometers in diameter. The crater caused by the impact is 200 kilometers in diameter. The energy generated by the impact, if converted into explosives, is equivalent to one million tons. Dust diffuses into the stratosphere through the atmosphere. It caused the darkness of the earth for months. During this period, many creatures, led by dinosaurs, became extinct.

2. Comet collision theory;

The "comet collision theory" is based on paleontologist David? Rapp and John? Sepkovsky's argument that "the extinction of paleontology occurs every 26 million years" is the beginning. Louis? Albalez gave this argument and his own theory to the astrophysicist-Charlie? Milla, later believed by Milla, periodically pushed comets to the earth because of the gravitational force of Nemesis, the half star of the sun.

3. Theory of orogeny;

At the end of Cretaceous, the swamp was dried up by orogeny, and many dinosaurs whose home was swamp could no longer survive. Because of the changes in the post-Qi Dynasty, 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 65,438+0,000-20 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 great changes in climate. The cold climate killed plants and dinosaurs died for lack of food.

5. Volcanic fire theory:

Because the volcano erupts, it spews a lot of carbon dioxide, causing the global greenhouse effect and causing 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.

The theory of ocean ebb tide with intransitive verb;

According to Barker, when the ocean ebbs and the land borders, creatures contact each other, which leads 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.

Seven. Warm-blooded animals say:

Some people think that dinosaurs were warm-blooded animals, so they could not bear the cold weather in the late Cretaceous and could not 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.

Eight. Fratricidal theory:

Some people think that the real reason for the extinction of dinosaurs is the result of their killing each other-carnivorous dinosaurs ate herbivorous dinosaurs, 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 died together.

Nine. Oppression theory:

The rapid increase in the number of dinosaurs led to the extinction of herbivorous dinosaurs with limited plants, and then carnivorous dinosaurs that ate herbivorous dinosaurs died because of lack of food. (Doubt: Why did dinosaurs suddenly increase after about 200 million years of ecological balance? The key to the establishment of this theory has also directly caused many scholars to review the reasons for the abnormal increase in dinosaur production. )

10. The mammalian prisoner said:

In the second half of Mesozoic, the ancestors of mammals existed. According to fossil records, 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 omnivores whose main food is insects. These small mammals have been eating dinosaur eggs since they found them.

My opinion: Is this really the case? If mammals beat dinosaurs, then with the increase of mammalian fossils, dinosaur fossils should gradually decrease, but in fact there is no such phenomenon of fossil alternation. In other books, the real increase in mammalian fossils was after the end of the dinosaur era. Moreover, dinosaur fossils suddenly disappeared. Therefore, the theory that dinosaurs were extinct by mammals cannot be established. )

1 1. The aging theory of species;

People think that the dinosaur's body was too big because it flourished for hundreds of millions of years. Moreover, bones such as horns are also extremely developed, which causes great inconvenience to life and eventually leads to extinction.

The most representative dinosaur brontosaurus is 25 meters long and weighs 30 tons. Because of his huge size, he lost his ability to survive. In addition, Triceratops and others also went to the road of self-destruction because of their expanding three horns and 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 with bones like deer that can run briskly. But why did this dinosaur die out at the same time? Moreover, in cold-blooded animals, abnormally developed bones and other parts are considered to be able to absorb external temperature and release internal heat to regulate body temperature, which has very favorable functions. Therefore, I suspect that the extinction of dinosaurs was due to the aging of species. )

Twelve. Alkaloid theory:

According to this theory, flowering plants began to appear in the last period of dinosaur existence, that is, the Cretaceous period, and some of them contained toxic alkaloids. Dinosaurs died of poisoning because of eating a lot of food. Because mammals can distinguish poisonous plants through taste and smell, but dinosaurs don't have this ability.

However, plants containing alkaloids did not suddenly appear in the late Cretaceous, but were already visible five million years before the extinction of dinosaurs. This theory can't explain why dinosaurs survived during this period.

In addition to the above twelve statements, there are other less well-known statements, such as "infectious diseases", "radiation from the universe or supernova explosion", "not taking Noah's Ark" and "vibration theory of the solar system". As for which is the best statement, it depends on everyone's thoughts, and there is no right or wrong. After all, the mystery of dinosaur extinction has not really been solved!

Who first discovered dinosaurs?

The story of prout-Garon-Garon

Mrs Mantell found the story of dinosaurs really romantic. Mr Mantell was able to explore the ownership of dinosaurs with a rigorous and realistic attitude, which was indeed the first step for human beings to study dinosaurs scientifically and understand them.

But in history, humans have long discovered dinosaur fossils, but at that time, due to limited knowledge, they could not explain them correctly.

As early as 1000 years ago, during the Jin Dynasty in China, dinosaur fossils were discovered in Wucheng County, Sichuan Province. But people at that time did not know that it was the remains of dinosaurs, but regarded them as the bones left by the legendary dragons.

Based on the clues found in a historical novel "Mr. milken's Wife", a researcher named Huster at the University of Reading in England recently announced that he had finally discovered the following fact: 1677, an Englishman named prout-Garonne-Garonne wrote a natural history book about Oxford. In this book, prout Gallon Gallon describes a huge fossil leg bone found in a quarry in the parish of Karovilla. Prout-Garonne-Garonne drew a good illustration of this fossil, and pointed out that this thigh bone is neither cow's, horse's, nor elephant's, but belongs to a giant bigger than them.

Although prout-Garonne Province-Garonne Province didn't realize that this fossil was a dinosaur, or even associated it with reptiles, the specimen he described with words and illustrations has been identified by later paleontologists as the thigh bone of a dinosaur called Megalodon, and this fossil was discovered 145 years before Iguanodon was discovered in Mantels. Therefore, Hastert thinks that prout-Garonne-Garonne should be the first discoverer and recorder of dinosaur fossils.

The origin of the name "dinosaur"

In fact, the history of human discovering dinosaur fossils must have a long history. Long before Mantel and his wife discovered Iguanodon, Europeans knew that there were many grotesque huge bone fossils buried underground. But at that time, people didn't know their exact ownership, so they were always mistaken for "the remains of giants." As for China, as early as 2,000 years ago, we began to collect large ancient animal fossils unearthed underground for medicine, and called these fossils "keels". Who can be sure that the name "keel" has nothing to do with the discovery of dinosaur fossils?

The oldest reptile fossils can be traced back to the Paleozoic Pennsylvanian period (365,438+million years ago-275 million years ago). Tracing back to the source, it evolved from amphibians. Amphibian eggs need to develop in water. Reptiles evolved eggshells to prevent water from escaping. This major reform enables reptiles to survive without water.

By the Mesozoic era from 225 million years ago to 65 million years ago, reptiles had become the masters of the earth, so the Mesozoic era was also called the reptile era. Large reptile dinosaurs appeared in the early Mesozoic. Herbivorous Liang Long and Lei Long are the largest land animals. Tyrannosaurus rex is a carnivorous dinosaur. There are also ichthyosaurs living in the sea and pterosaurs living in the air.

Reptiles have multiplied on the earth for about 654.38+0.5 billion years. Among the animals of this era, dinosaurs are the most widely known. When people mention dinosaurs, they will see a huge and fierce animal. In fact, there are also small and docile dinosaurs among dinosaurs.

Dinosaur is a kind of vertebrate reptile, which was once produced in Mesozoic land swamp and had a long neck and tail. The hind limbs are longer than the forelimbs and have tails. Some of them are carnivorous, and some are herbivorous. They are huge and can be considered as the largest terrestrial animals. Its physique is similar to that of the oldest crocodile and beak in lower species, and slightly similar to that of birds in higher species.

The study of dinosaurs depends entirely on fossils. Paleontologists infer their shapes and habits from their fossils. According to paleontologists, dinosaurs are like living animals: there are big ones and small ones; Some people walk on two legs; Some people walk on four legs; Some eat plants, some eat animals; Some skin is smooth, and some skin has scales or bone plates. What they have in common is that all dinosaurs have small brains and lay eggs on land (as do all reptiles).