CAMBRIAN CAMBRIAN (5.4 ~ 5. 1 100 million years ago)-The great development of marine invertebrates The CAMBRIAN is the first epoch of Phanerozoic Paleozoic in geological time division, which is about 540 ~ 5 1 100 million years ago. Cambrian is the beginning stage of modern life, and it is also the period when modern life on earth begins to appear and develop. The CAMBRIAN is far away and strange to us, and the characteristics of the earth and continent in this period are completely different from today. Cambrian is often called "trilobite age" because there are more mineralized trilobite crusts in Cambrian rocks than in other groups. At that time, the appearance of many advanced marine invertebrates and the preservation of a large number of fossils made it possible to study the situation of the biological world at that time, divide and compare the strata by biostratigraphy, and then study the relatively complete development history of the organic world and the inorganic world. However, the Chengjiang fauna tells us that all kinds of animals living on the earth appeared almost simultaneously shortly after the Cambrian. Cambrian is the beginning of Phanerozoic, which marks a new scene in the evolutionary history of life on earth. In just a few million years after the beginning of Cambrian, a large number of multicellular organisms suddenly appeared, including the ancestors of almost all biological groups. This explosive biological evolution event is called "Cambrian explosion". Marine invertebrates with shells and bones tend to flourish. They live in benthic organisms and feed on tiny algae and organic particles. Among them, the most prosperous is the arthropod trilobite, so the Cambrian is also called the "trilobite era", followed by brachiopods, ancient cups, echinoderms and gastropods. The biological form of CAMBRIAN is very strange, which is very different from the creatures we see on earth now. The famous ones are the Early Cambrian Chengjiang Fauna in Yunnan and the Middle Cambrian Burgess Shale Biota in Canada. Marine invertebrates and seaweed dominated the Cambrian biological world. Many advanced invertebrates, such as arthropods, echinoderms, mollusks, brachiopods and graptolites, are representative. Among them, trilobites are the most important arthropods, followed by brachiopods. In addition, ancient cups, ostracods, soft-tongued snails, odontoids and nautilus are also very important. In addition to conodonts, there are many other representative higher chordates, such as Huaxia eel, Yunnan fish and Haikou fish in Chengjiang fauna in Yunnan, China, dermatophytes in Burgess shale in Canada, and duck scale fish in Upper Cambrian in the United States. In the humid lowlands, there may be lower plants such as moss and lichen, but they still lack real rhizome tissue, so it is difficult to survive in dry areas; Invertebrates have not evolved the ability to adapt to life in the air. There were no real terrestrial creatures in CAMBRIAN, and the continent was lifeless and desolate. Paleontology used the word "big bang" to describe the sudden explosion of biodiversity. According to the sudden diversity and complexity of trace fossils and small shell fossils in the early CAMBRIAN, the theory of "CAMBRIAN explosion" was put forward before the discovery of Chengjiang fauna, but little was known about the characteristics of animals and animal communities produced by "CAMBRIAN explosion". Even the famous Burgess shale fauna in Canada was more than 6.5438+million years later than the "CAMBRIAN explosion", which could not answer the specific life in the ocean in the early CAMBRIAN. The geological age of Chengjiang fauna is in the period of "Cambrian explosion", which makes us really see the true face of fauna 530 million years ago. All kinds of animals originated rapidly and appeared immediately during the "Cambrian explosion", but now all kinds of animals living on the earth exist almost at the same time, instead of slowly changing after a long period of evolution. It pushed the history of animal diversity to the early CAMBRIAN. The biological forms of CAMBRIAN are very strange, which are quite different from those on earth. The oldest fish also appeared in this era, which is the Haikou fish (Haikou fish) excavated from Chengjiang fauna. CAMBRIAN: 570-505 million years ago, CAMBRIAN was the first period of Paleozoic. During this period, a large number of invertebrates lived in the ocean, and many animals have multiplied to this day. These biological categories include arthropods (invertebrates with joints in their body shells) and mollusks (invertebrates with soft bodies, which rely on hard shells to protect themselves). The geological period before Precambrian. Also known as Precambrian. Precambrian began in the earliest geological stage and ended about 570 million years ago. It is called the stratum formed in this period, which is located under CAMBRIAN. Precambrian is divided into Archean and Proterozoic. Now Archean and Proterozoic are widely used to represent its early and late stages respectively, and the dividing line was 2.5 billion years ago. 1930, G.H. chadwick divided all geological periods into two parts: before Cambrian, it was called Phanerozoic; The geological period since CAMBRIAN is called Phanerozoic. In recent years, due to the discovery of mollusk fossils in the upper Precambrian strata, which are divided into Archean and Proterozoic, the term cryptozoic has tended to be no longer used. Precambrian strata are widely exposed in the world, and the area with large outcrops is called shield or craton. The main shields are Baltic shield, Siberian shield, China shield, Canadian shield, African shield, South American shield, Australian shield and Antarctic shield. Archean rocks in shield area are mostly greenstone, granite and sedimentary metamorphic rocks, accompanied by basic volcanic rocks. Banded iron-bearing formations were widely produced in Precambrian rocks 2 billion years ago, and then continental red beds appeared. This change may reflect the development of early biological oxygenation. Moraine is a special type of Precambrian, which is obviously distributed in canadian shield and southern Africa in the upper part of Lower Proterozoic. Moraine is distributed in Upper Proterozoic, Asia, Europe, America and Australia. There are few rocks and minerals aged between 3.5 billion and 4.6 billion years ago. It is no longer possible to determine the time of its initial formation by radioactive measurement. The oldest sedimentary rocks and volcanic rocks that can be determined are no more than 3.8 billion years old. Sedimentary rocks and volcanic rocks formed on the earth's surface about 2.7 billion to 3.8 billion years ago have undergone deformation and metamorphism. The metamorphic sequence of the oldest moderate sedimentary rocks and volcanic rocks was found in the lower part of the Witwatersrand basin in South Africa. There are few Precambrian fossils, but traces of protobacteria and algae have been found in paleostrata 3 1 100 million years ago. Precambrian is characterized by plankton and protozoan microfossils from seedless to nucleated and unicellular. About 2 billion years ago, the atmosphere began to accumulate oxygen, and after there was a considerable amount of oxygen in the atmosphere, biology developed. Stromatolites derived from blue-green algae are widely distributed in the late Precambrian period. About 680 million years ago, multicellular metazoa with soft tissues appeared, called Ediacaran fauna. The climatic conditions in most periods of Precambrian are basically unknown, but it is known that extensive glaciation occurred in its late period (about 700 million years ago). Precambrian rock mass is an important source of metal minerals, especially iron, nickel, gold, uranium and copper. Iron ore is mainly sedimentary, but there may also be large igneous magnetite bodies. 75% of the world's nickel production comes from large intrusions in sudbury, Ontario, canadian shield. The gold produced in Precambrian rock mass exceeds the sum of other geological bodies. Now half of the world's gold production comes from Precambrian conglomerate in Witwatersrand, South Africa. Other valuable minerals include platinum, silver, lead, zinc, chromium, cobalt, manganese, graphite, mica and talc. In the shallow sea 530 million years before the Cambrian explosion, life experienced a revolutionary large-scale evolution, and the earth, which had been silent for 4 billion years, suddenly became alive. This is the "Cambrian explosion" that once puzzled Darwin. The research on "Chengjiang Fauna and Cambrian Outbreak", which was awarded the first prize of the National Natural Science Award a few days ago, is to solve the amazing secret in the history of life on the earth-life has existed on the earth for 4 billion years, but it has spent 3.5 billion years at the level of single cell and lower life. Until the Cambrian 530 million years ago, at the moment of the magical "Cambrian life explosion", all the early embryonic forms of modern life appeared on the earth like the "Big Bang". The "Cambrian explosion" is a problem that puzzles Darwin. Today, when people generally agree with Darwin's theory of evolution, it is still before people to fully reveal and reasonably explain the true face of the "Cambrian explosion" and explore the origin of many animal species. Tens of thousands of fossils have been found in Chengjiang County, Yunnan Province, China, which is the only large-scale paleontological fossil park in the world. Scientists in China have sharpened their swords for 20 years. Through the discovery and study of the fossils of Chengjiang fauna, the overall outline of the "Cambrian explosion" was revealed for the first time in the world, and it was confirmed that almost all animal ancestors stood at the same starting line. This achievement is "an important development of Darwin's theory of evolution". The scientific research project named "Chengjiang Fauna and Cambrian Outbreak" completed by three scientists won the first prize of the National Natural Science Award in 2003, and only 28 achievements have won this honor since the founding of New China. Chen, Hou Xianguang and Shu Degan from China Academy of Sciences, Yunnan University and Northwest University shared this honor a few days ago. What is the "Cambrian explosion"? The fossils of Chengjiang fauna in China reveal the overall outline of the CAMBRIAN explosion for the first time in the world, which has attracted worldwide attention. So what are CAMBRIAN and CAMBRIAN explosion? Hou Xianguang, the first discoverer of Chengjiang fauna fossils and a professor at Yunnan University, gave a detailed answer. Cambrian is the first epoch of Phanerozoic Paleozoic in geological history division, which is about 540 million ~ 565.438+0 billion years ago. Cambrian is the beginning stage of modern life, and it is also the period when modern life on earth begins to appear and develop. The CAMBRIAN is far away and strange to us. The characteristics of the earth and the mainland at that time were completely different from today. Cambrian is often called "trilobite age" because there are more mineralized trilobite crusts in Cambrian rocks than in other groups. However, the Chengjiang fauna tells us that all kinds of animals living on the earth appeared almost simultaneously shortly after the Cambrian. Paleontology used the word "big bang" to describe the sudden explosion of biodiversity. The geological age of Chengjiang fauna is in the period of "Cambrian explosion", which makes us really see the true face of fauna 530 million years ago. All kinds of animals originated rapidly and appeared immediately during the "Cambrian explosion", but now all kinds of animals living on the earth exist almost at the same time, instead of slowly changing after a long period of evolution. It pushed the history of animal diversity to the early CAMBRIAN. Why did so many rich creatures appear in CAMBRIAN? Scientists have put forward many hypotheses, but at present there is no clear and conclusive evidence and convincing explanation. The "CAMBRIAN explosion" is still an unsolved mystery. The discovery process of the "CAMBRIAN explosion" hat Tianshan Mountain looks like a plain hill, like a round hat worn there. People who come and go will not look at this ordinary yellow mound. Scientists are all very excited to come here. However, after a long silence, this humble mountain bag in Chengjiang County, Yunnan Province, is now regarded as a sacred place by paleontologists, and an amazing secret in the history of life on earth has been gradually solved: 530 million years ago, an extremely important event was staged in the shallow sea here-life experienced a revolutionary large-scale evolution, and most of it was the "door" level, the largest taxonomic unit below the "boundary". Boom, the earth, which has been silent for 4 billion years, suddenly became lively. The blue planet finally has bright colors. "In an instant" (this process is actually about 2 million years, but compared with the 3.5 billion years of the earth's biological history, 2 million years is like L minutes in a day), many animals that have never been seen on the earth suddenly appear in the ocean, and paleontologists even use "outbreak" to describe this suddenness; They have different shapes, ranging from miniature animals with only a few millimeters to giant monsters with huge eyes and terrible claws with handles, covering almost all existing animal categories. In other words, the ancestors of all animals that flew in the sky, ran underground and swam in the sea almost all appeared at that time. Many multicellular animals, including humans, probably started their own evolutionary history from here. Near Kunming today, from east to west, including Malong, Chengjiang, Changchongshan, Minshan, Haikou and Wuding, there are Cambrian sedimentary shales exposed on the surface. At present, scientists are mainly exposed to Maotian Mountain, a corner of the mountain range. At present, there are only 35 phyla among tens of millions of living creatures on the earth, but more than 20 phyla first-class systems (excluding some extinct phyla first-class animals) have been found in Chengjiang fossils, and new phyla are being discovered continuously. This illustrates a key problem. In the Early Cambrian, the basic system of animal diversity was established. Chengjiang fauna and Cambrian explosion Chengjiang fauna are a multi-class fossil fauna, which let us truly see the true face of the fauna 530 million years ago. However, how did Chengjiang Fauna, known as "one of the most amazing discoveries in the 20th century" "surface"? "Discovery has its contingency, but it also contains inevitability. If you want to make real achievements in science, you must work harder and more carefully than ordinary people. The discovery of Chengjiang fauna is the result of painstaking and meticulous field work. " Hou Xianguang, the discoverer of Chengjiang fauna and a professor at Yunnan University, told the author. The study of geology and paleontology in Chengjiang has a history of nearly a hundred years. As early as 1909 and 19 10, French scientists made a detailed study of the geology and paleontology in this area and published research monographs. After the founding of New China, scholars and research and teaching units at home and abroad have carried out a lot of research work here. Of course, if someone can predict the existence of Chengjiang fauna in this area, this great discovery will certainly not be postponed until the 1980s, nor will it fall on an ordinary young researcher. Time goes back to1June 5, 984. On this day, Hou Xianguang, who worked in Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, just got his master's degree for more than two years, left Nanjing and arrived in Yunnan by train on the 9th to collect the fossils of high muscle insects for his professional research. However, the progress of his work is not satisfactory. On July 1 day, Hou Xianguang shifted his focus to Maotian Mountain in Chengjiang County in the rain. On this day, he and a villager in nearby Dapotou village worked very hard in the rain. At 3 pm, a lifelike animal fossil was exposed on the wet rock cleavage surface, sweeping away Hou Xianguang's fatigue. This specimen is 4 cm to 5 cm long, and its body consists of two back shells, with legs and limbs swinging forward symmetrically distributed. "I was dumbfounded when I suddenly found this well-preserved software accessory specimen. The whole body blood seems to have stopped flowing, and my hand holding the specimen can't help but tremble. " Hou Xianguang is still excited about the discovery of this specimen named Rona Long Tail. On this day, Hou Xianguang and the villager didn't leave until dark. They walked along the winding mountain road for 1 hour before returning to their residence in Dapotou Village. "I put some important specimens under the bed. I was so excited that I couldn't sleep all night. I got up and looked at the specimens under the bed from time to time. This has also changed my research direction. " Hou Xianguang, who originally went to look for the fossils of high muscle insects, hit the nail on the head and laid the goal and direction of his future work. 65438+1 July 19841day is undoubtedly a milestone in the history of paleontology in the world. Since then, "one of the most amazing discoveries of the 20th century" has gradually unveiled its mystery. Almost all animal ancestors once stood on the same starting line. Since Darwin founded the theory of biological evolution in 1859, people began to realize the strange phenomenon of the sudden explosion of life in the early CAMBRIAN, which occurred in the early Paleozoic 540 million to 530 million years ago. Darwin also admitted in the Origin of Species that he could not explain the fact that Cambrian fossils suddenly appeared. The "Cambrian explosion" stumped countless scientists, and exploring the origin of life is still a world problem. At present, the origin of any phylum or subfamily has not been generally solved, and it is waiting for the real and reliable early fossil records with rich biological information to provide direct evidence. Chengjiang fauna is the best scientific window for people to explore the mystery of the source of life for a long time. It took less than 2 million years from the small shell fauna to the Chengjiang fauna, which was the most critical scene of the Cambrian explosion and the great birthday of the basic system of animal diversity. During 1909, foreign scientists discovered the Middle Cambrian Burgess shale fauna in Canada. In the past century, foreign scientists once dominated the research field of early life on earth. They were considered as the most representative fossil fauna of the Cambrian explosion, so Bourguie was called "the paradise of paleontology". "The CAMBRIAN explosion theory was put forward before the discovery of Chengjiang fauna, but little is known about the structural characteristics of animals and animal communities produced by CAMBRIAN explosion. Even the famous fossils of Burgess shale fauna in Canada are later than the CAMBRIAN explosion 10 million years, which cannot answer the specific life in the early CAMBRIAN ocean. " Three scientists told the reporter, "The geological age of Chengjiang fauna was in the period of Cambrian explosion, which made us really see the true face of fauna 530 million years ago. All kinds of animals originated rapidly and appeared immediately during the Cambrian explosion, but now all kinds of animals living on the earth exist almost at the same time, instead of slowly changing after a long period of evolution. It pushed the history of animal diversity to the early CAMBRIAN. " "Chengjiang fauna is an important discovery of paleontology in the 20th century, which provides a new answer to the problem of early biological evolution and its' big explosion' in the early CAMBRIAN." The jury of the National Natural Science Award spoke highly of this achievement: "This study has established a number of extinct higher-order biological categories and systematically studied the early evolution of some existing biological categories ... It is a major original work, and the research results further affirm the mutation mode of biological evolution, which is an important development of Darwin's evolution theory and has great scientific value and far-reaching influence in the world. Scientists believe that the excavation and study of Chengjiang fauna by three scientists revealed the overall outline of the colorful CAMBRIAN explosion animal world, and confirmed that the CAMBRIAN explosion was the starting point of history, whether it was biological fauna or subphylum, as well as complex life forms. It challenges the theoretical model of bottom-up inverted cone evolution of life formation on earth and provides a basis for the theoretical model of top-down life explosion formation. The discovery and research of Chengjiang fauna has aroused strong concern of the international community. An academician of the Royal Academy of Sciences believes that Chengjiang Fauna "will always be a scientific building"; The New York Times commented that this is "one of the most amazing discoveries of the 20th century"; The evaluation of Science News in the United States is more vivid: "Paleontologists who have been searching for the origin of life in the early darkness of the earth for a long time and are desperate for it are extremely happy with these brand-new fossil evidences. "The author of this project has published more than 90 papers, including 14 papers in internationally renowned magazines Nature and Science. In the ocean 530 million years ago, the CAMBRIAN creature "Dinosaur in the Sea" was the most ferocious predator. It has a pair of giant eyes with handles, a pair of segmented giant forelimbs for catching prey quickly, a beautiful big tail fan and a pair of long tail forks. Although it is not good at walking, it can swim quickly. The giant mouth with a diameter of 25 cm can prey on any large creature at that time, and there are annular external teeth in the mouth, which poses a great threat to those animals protected by mineralized exoskeletons. This is a carnivore with strong attack ability, and its individual can reach more than 2 meters at most, while most other animals were only a few millimeters to a few centimeters on average at that time. The most complete fossil of strange shrimp appears in the shale of Maotianshan Mountain. 1992, a highway was built on the northern slope of Maotian Mountain, which was pushed out by bulldozers for a huge section, giving the opportunity to find strange shrimp fossils. At the beginning of the first specimen, only the end of the front appendage was exposed. Driven by curiosity, Zhou of Nanjing Institute of Geology and Paleontology restored it in the field. When a pair of complete front appendages and head were exposed, she couldn't help shouting excitedly. The appearance of the first exotic shrimp specimen leads to the appearance of the third complete exotic shrimp. In fact, this "third" strange shrimp fossil was collected by Zhu of Nanguo Institute as early as 1990, but its strange shape was confusing at first, so it was left out in the office tray for nearly two years. With the recovery of the specimen, a complete and fierce predator image appeared in front of people. The diet of kiwi shrimp may include other carnivores. It has such a big body, such a big mouth and such a pair of big catching organs. It can prey on the biggest creatures at that time, and it will never only eat the creatures at the bottom of the food chain, because its claws are too thick, so it is not so easy to catch tiny food. No one would have thought that kiwi shrimp was not the "fittest" in the ocean at that time. It can be called the "Big Mac" in the ocean. It is at the top of the food chain and can easily catch enough food, but no other creatures can threaten its survival. However, just like dinosaurs that once dominated on land, kiwi shrimp has long since become extinct. When and why did it disappear from the earth forever? This is another unsolved mystery.