The age of dinosaurs: Mesozoic

The history of life on Earth can be traced back to 4 billion years ago, but the most exciting part did not officially kick off until the Cambrian period of 540 million years ago. Starting from the Cambrian, the earth went through the Paleozoic, Mesozoic and Cenozoic in turn. If you want to choose the most exciting era from these three eras, many people will not hesitate to choose the Mesozoic era, because this era has the most amazing and magnificent life-dinosaurs.

There were not only dinosaurs in the Mesozoic, but also other giant animals, such as pterosaurs, ichthyosaurs, mosasaurs and so on. Although the Mesozoic is a long time ago, most of the animals and plants on the earth today, such as mammals and birds, have already appeared at that time. Therefore, the Mesozoic played an important role in connecting the past and the future.

Recovery is just to welcome the next extinction

The opening of the Triassic was not good, it should be said to be very bad, because life on earth has just experienced the terrifying Permian mass extinction, less than 5% of the species survived, leaving them a whole new world.

The world of the Triassic was completely different from today. All the continents were connected together, and this continent was called the “pancontinent.” The fringe of the pan-continent receives seasonal precipitation because it borders the ocean. The vast inland is different, with water shortage and drought and harsh climate.

Since the land is so short of water, let’s replenish it well. 230 million years ago, the global precipitation model started, but the heavy rain lasted more than 1 million years. The rain fell on the ground and formed a flood, which was carried into the ocean with sediment. The shallow sea, which was restored in the early Triassic period, could not withstand such a toss, and marine life became extinct one after another. This continuous precipitation was called the “Carnian Alluvial Event”.

After the Carnian flood event, the earth returned to normal, and just as life was about to take a breath, the mass extinction came again. This mass extinction was due to a large-scale volcanic eruption, a large amount of carbon dioxide and toxic substances entered the atmosphere, and then brought high temperature and acid rain, life began to mass extinction, this is the Triassic-Jurassic extinction event. Fortunately, the Triassic-Jurassic extinction event was far less intense than the Permian mass extinction, and it did not drive all lives to extinction.

The Triassic-Jurassic extinction event was indeed a catastrophe for the species that disappeared or declined in this disaster, but it was an opportunity for other species, such as dinosaurs. The earliest known dinosaurs appeared 230 million years ago. They have passed the double test of the Carnian flood event and the Triassic-Jurassic extinction event, and finally successfully passed the test, and they will be greeted by the most beautiful era. !

On March 19, 1982, paleontologists Jack Sepkoski (Jack Sepkoski) and David M. Raup (David M. Raup) published a research report on Science, reporting on species after the Cambrian outbreak We have made statistics on mass extinction events and identified five mass extinction events:

Continental drift

Start the era of dinosaurs ruling the earth

The beginning of the Jurassic was the Triassic-Jurassic extinction event, but since the beginning of the Jurassic, the earth ushered in a stable period of 140 million years, and the most beautiful era officially began.

The climate label of the Jurassic is warm and humid. The tropical and subtropical regions extend from the equator to 60° north-south latitude, which is equal to the position of Siberia and Canada today. The remaining area belongs to the temperate zone, including the Antarctic and Arctic, so there were no glaciers on the Jurassic Earth, and snow was only a rare thing on the tops of high mountains.

The key reason for changing the climate is the division of pan-continents. The original “steel plate” of the land began to separate from the early Jurassic. The ocean invaded the gaps between the land blocks to form a new ocean, one of which was called the Tethys Sea. In the late Jurassic period, the western part of the Tethys Sea flooded Europe, leaving only a series of islands, and the famous Archaeopteryx and Compsognathus lived here. The eastern part of the Tethys Sea submerged today’s Qinghai-Tibet Plateau, that is to say, Sichuan and Chongqing were not far from the sea at that time.


Cycad, commonly known as iron tree

A plant that existed on the earth in the Jurassic era-horsetail

Because it was close to the sea, the water vapor from the ocean brought abundant precipitation to the entire southern China including Chongqing in the late Jurassic. Coupled with the greenhouse effect caused by the high concentration of carbon dioxide at that time, the climate of Chongqing in the late Jurassic was more Today, it is still warm and humid, and the annual average temperature is about 10 ℃ higher than today. It belongs to the tropical monsoon climate.

As mentioned above, Chongqing in the late Jurassic was definitely not short of rain, and the terrain was not as violently ups and downs as today. Not only was the terrain relatively flat, but also lower-lying than the surrounding areas, so the rivers formed by precipitation gathered here. At the same time, a vast lake delta is formed, and a large number of aquatic animal fossils and silt deposits in the strata are direct evidence.

Lakes and rivers only submerged part of the land, and in more places there are endless green forests. This green stretches to the distance, and you can’t see it at a glance. Different from today’s forest composition, since the late Jurassic angiosperms have just appeared, there are far fewer varieties and such tall statures today, and paleontologists have not even found angiosperm fossils in the strata here. Since the angiosperms may not have appeared, the large forests are composed of conifers and ginkgo plants belonging to the gymnosperm family. These big trees with straight trunks strive to grow to the sky, and some can even exceed 100 meters in height!

The conifers and ginkgo plants located in the uppermost layer of the forest are luxuriantly connected with their branches and leaves, covering the sky and blocking most of the sunlight. Therefore, even at noon when the sun is scorching, the light in the lower layers of the forest is obviously insufficient, and even a little gloomy. But this is the favorite environment of ferns-low ferns occupy the lower layer of the forest, and the slightly taller Alsophila spinulosa and cycads ② are located in the middle layer.

Except for the lush large forest, the wetland occupies a large area between the forest and the lake. There are no tall trees to see here, so the sun is very abundant, and the vegetation is dominated by low horsetails and some ferns. Although the wetland may not look eye-catching, it is home to a rich variety of animals and plants, with extremely high biodiversity, and is an important part of the late Jurassic ecosystem.

Lakes, forests, and wetlands, this is what Chongqing looked like in the late Jurassic period. The unique and superior natural environment attracted a large number of dinosaurs to live here. Take the Shangshaximiao Formation where dinosaurs are most concentrated in Chongqing as an example: the largest animals are those sauropod dinosaurs with small heads, long necks and walking on all fours. Their niche is equivalent to today’s African savannah. Elephants on the mountain have very few natural enemies after they reach adulthood. The medium-sized herbivorous dinosaurs are Chungkingsaurus, Giant Spinosaurus, Tuojiangosaurus, etc. They all belong to the Stegosaurus genus, with a pair of bone plates on their backs and their tails. There are sharp bone spurs, and the ecological niche is equivalent to that of the African buffalo, who dare to fight desperately in the face of danger; the small herbivorous dinosaurs are Yandusaurus, etc., these little guys have no defense structure, and run wild on two legs, the niche is equivalent In the small antelope. Carnivorous dinosaurs are of course the most feared by herbivorous dinosaurs. Carnivorous dinosaurs of different ranks live in the Shangshaximiao Formation: the largest Yongchuan dragon is equivalent to a lion and can threaten large sauropod dinosaurs; the middle-weight Sichuan dragon is equivalent Yu Leopard is able to deal with stegosaurus easily; the smaller Chinese phantomsaurus is equivalent to a wild dog, hunting down small dinosaurs by speed.

In addition to dinosaurs, Chongqing in the late Jurassic period also lived with flying pterosaurs, swimming crocodiles, turtles, salamanders and so on. Together they constituted a complete ecosystem, and Chongqing has also become an out-and-out Jurassic Park.

Going to the top will usher in the end

The Cretaceous period continued the beautiful era that began in the Jurassic period. Life on the earth was thriving, and dinosaurs were still the most powerful animal group in the terrestrial ecosystem.

During this period, the land mass was split up at an accelerated rate, and it has already taken on what it looks like today. By the late Cretaceous, the sea level was more than 100 meters higher than today, and one third of the land was below sea level, becoming a prosperous shallow sea where marine life was concentrated. Compared with the division of land, the Cretaceous climate experienced a process of cooling first and then heating up, but the overall stability was stable and did not cause any major problems to life.

The dinosaur family did not go downhill in the Cretaceous, but went to the top. The types of dinosaurs became more abundant in the late Cretaceous-there appeared the ferocious and strong Tyrannosaurus family, the horned horned dragon family with the head shield, the armored Ankylosaurus family, the clever and cunning galloping dragon family, and the flying like chickens. The dragon family and so on. As the species of dinosaurs increased, their size also became larger: the Argentinosaurus living in South America was about 35 meters long and weighed nearly 80 tons, making it the largest known dinosaur and the largest terrestrial animal; life In North America, Tyrannosaurus rex is 12-13 meters long and weighs nearly 10 tons. It is the largest known carnivorous dinosaur and the largest terrestrial carnivore.

In addition to dinosaurs, many animals have also embarked on the path of large-scale in the Cretaceous: dein and emperor crocodiles are all prehistoric giant crocodiles with a body length of more than 10 meters; mosasaur evolved into a super sea monster with a body length of nearly 20 meters; aeolian pterosaur wings Extending more than 12 meters, it looks like a small airplane after takeoff; even the ammonites in the ocean are getting bigger and bigger, and the shell diameter of the carpan ammonite is 2.55 meters.

While those traditional animals are getting bigger, a revolution is coming quietly, the symbol is the flower. Flowers are a sign of angiosperms. Although the earliest angiosperms appeared in the late Jurassic, they still swept the world during the Cretaceous period. The prosperity of angiosperms has made the once-green world colorful, but their significance is much more than that. New birds and mammals have also developed and grown with the help of angiosperms.

At the end of the Cretaceous, the volcano on the Deccan Plateau ③ began to erupt violently, which seemed to be just an episode. 66 million years ago, an asteroid with a diameter of 10 kilometers hit the Yucatan Peninsula of Mexico today. The impact of this impact is equivalent to 40 times the detonation power of a global nuclear weapon. Catastrophes, including shock waves, earthquakes, tsunamis, fire storms, volcanic eruptions, etc. brought about by the impact, swept across the globe, leading to the Cretaceous-Paleogene extinction event, and 80% of the earth’s species went extinct, including non-bird dinosaurs. . The impact of an asteroid has brought an end to the most beautiful era, but life on earth is not over, they will come back in the next new generation!