Name: Chinese Sturgeon Age: Early Cretaceous 120 million years ago
<b>Triassic</b>
The Triassic, from 250 million to 199 million, was the first epoch of the Mesozoic Era, a period of rise for reptiles and gymnosperms. After the Haixi Movement, many troughs were converted into mountain systems, the land area expanded, and some inland basins were produced in the platform area. This new paleogeographic condition led to changes in sedimentary facies and the biological world. From the Triassic period onwards , continental sediments were abundantly distributed around the world , particularly in China and other parts of Asia. In terms of paleoclimate, the early Triassic inherited the characteristics of drought at the end of the Permian; after the middle and late periods, the climate transitioned to humid heat, resulting in the coal-bearing deposition of red rock formations and the development of xerophytes to hot and humid plants. Plant geography also diverged at the same time.
The beginning and end of the Triassic period were marked by an extinction event. Today it is generally believed that there was no land or ice at the poles at that time. There was only one continent on Earth at that time, so the coastline at that time was much shorter than it is today.
Since the Triassic began with an extinction event, its organisms began to diverge violently. This is when the suborder Hexapods appeared, as may the first angiosperms and the first flying vertebrates (pterosaurs).
Among the fossils in Li Xuchu's collection, belonging to the Triassic period are: pre-thick ammonite, fan-shaped retibei, Chinese osprey tsui shellfish, thin set of sea fans, primitive sponge needles, large-leaf chestnuts, Chinese willows, wood thieves, cycad hemlocks (plant fossils), sand blue wood thieves, pleated clams, lattice ferns, scaly tooth fish and so on.
<b>Jurassic</b>
The Jurassic is a geological age, about 199.6 million years ago (error value of 600,000 years) to 145.5 million years ago (error value of 4 million years), the second period of the Mesozoic Era, beginning with the Triassic - Jurassic extinction event. Although the rock markers of this period are very obvious and clear, the exact time of its beginning and end, like other ancient geological epochs, cannot be determined very precisely. The name Jurassic is taken from the Jurassic Mountains on the borders of Germany, France, and Switzerland. The super-continent Pangea really began to split at this point, with seams in the continental crust forming the Atlantic Ocean, Africa beginning to split from South America, and India preparing to move to Asia.
There have been some important events in the history of biological development that attract attention, such as dinosaurs becoming rulers of the land, the emergence of pterosaurs and birds, the beginning of the development of mammals, and so on. Terrestrial gymnosperms developed to their peak. Freshwater invertebrates are bivalves, gastropods, leaf limbs, mesozoans and insects that develop rapidly. Marine ammonites, bivalves, and arrowstones are still important members, and echinoderm sea urchins have occupied an important position since the Jurassic Period.
Among the fossils collected by Li Xuchu, there are many fossils belonging to the Jurassic period, such as Psittacosaurus, Dinosaur Egg, Lingyuan Hidden Dragon, Hand Clam, False Hinge Mussel, Pavlov Ammonite, Thorn Nail, Ancient Mosquito, Nakamura Mussel, Strangled Bee, Pure Thorn Nail, Chinese Diving Bug and so on.
<b>Cretaceous</b>
The Cretaceous is the last epoch of the Mesozoic Era, beginning 145.5 million years ago and ending 65.5 million years ago, spanning 80 million years.
The Cretaceous – Tertiary extinction event was one of the worst mass extinction events of geological age, with most species, including dinosaurs, perishing. During this period, the continents were separated by the oceans, and the earth became warm and arid. Flowering plants, the largest dinosaurs appeared during the period, many new dinosaur species began to appear, dinosaurs still ruled the landing grounds, pterosaurs glided through the sky, and huge marine reptiles ruled the shallow seas. The first snakes, moths, and bees, as well as many new small mammals, also appeared.
Gymnosperms and ferns on land in the early Cretaceous period still dominated, with conifers, cycads, ginkgo biloba, euthanthis and knots forming the main flora. Angiosperms began to appear in the early Cretaceous Period, increased greatly in the middle period, and dominated among terrestrial plants in the late period, such as beech, banyan tree, magnolia, maple, oak, poplar, camphor, walnut, plane, etc., which are close to the appearance of the Cenozoic flora.
Among the fossils collected by Li Xuchu, those belonging to the Cretaceous period are biconvex Yongkang snail, pre-Baikal snail, actress Jie, turtle, dinosaur egg, Chinese sturgeon, Chinese salamander, lobster fossil, dragonfly fossil, thick plate ammonite, medium white fly, etc., and many kinds of insect fossils.
<b>Early Tertiary</b>
It started 65 million years ago and ended 23.3 million years ago. The Early Tertiary period consisted of the Paleocene, Eocene, and Oligocene.
Paleocene (65 million years ago): With the exception of dinosaurs, some reptile taxa that survived the extinction of Cretaceous clusters continued to live, and mammals and birds retained some of their ancient characteristics and developed further, with the emergence of early horses, elephants, and bears in mammals. Plants of the Asteraceae family began to appear in the plant kingdom.
Eocene (53 million years ago): Herbaceous plants emerged and continued to flourish alongside legumes and Asteraceae. Ancient fauna were gradually replaced by the ancestors of modern fauna, and 40 million years ago, herbivores and monkeys began to appear, and some mammalic taxa (whales, dolphins) returned to life in the ocean. Foraminifera develop and flourish.
Oligocene (36 million years ago): The earliest apes appeared, and large mammals and birds were widely distributed on Earth, such as the giant rhinoceros, the largest mammal on land, ancient and modern times, such as rhinoceros. A large amount of land is covered by grasslands.
In the Tertiary Period, angiosperms flourished. Except for the pine cypress, which is still important, the rest of the gymnosperms are declining. Ferns are also greatly reduced and mostly confined to warmer regions. The changes in vertebrates are mainly manifested in the decline of reptiles, and mammals, birds and bony fish have taken their place, rising and flourishing. In the early Tertiary Period, ancient and primitive mammals still lived; in the middle period, the ancestors of modern mammals appeared one after another, gradually replacing ancient and primitive mammals.
<b>Late Tertiary Period</b>
23.3 million years ago – 2.4 million years ago, the late Tertiary Period, including the Miocene and Pliocene.
Miocene (23 million years ago): Primates occupied an important position in the Miocene, such as the wide distribution of forest apes, by the end of the Miocene, apes and large apes evolved separately, apes radiated evolution and reached the ape of evolution, the emergence of Siva ancient apes -) with living ape and human characteristics of the great apes.
Pliocene (5 million years ago): The earliest human beings appeared, Australopithecus australis.
The division and contrast of late Tertiary strata has its own unique and complex history. The Late Sino-Neogene system was widespread throughout the country, and only south and northeast China and northeast China had not yet found mammal fossils. North of the Yellow River and west of the Fenhe River are mainly soil-like accumulations, the so-called three-toed horse laterite, and the east of the Fenhe River is precipitated by the river and lake phase; it is found less between the Yellow River and the Yangtze River, and there is limestone in Zhengzhou and Xiangfan; and yunnan is more swampy and has lignite. In the 1970s, three-toed horse fossils were also found on the northern slope of Theaboang Ma Peak in Tibet. The Upper Neogene is found less, and is only scattered in Shaanxi, Shanxi, Hebei and other provinces and basins.
<b>Quaternary</b>
The Quaternary period is about 2.4 million years old. After that mass extinction 65 million years ago, the Earth entered the Cenozoic. The Cenozoic is the latest stage in the history of the earth, and the Quaternary is the last epoch of the Cenozoic, which can also be divided into Pleistocene, Holocene and so on. The face of the Quaternary biosphere is very close to that of modern times. The evolution of mammals is most evident at this stage, and the emergence and evolution of humans is one of the most important events of the Quaternary Period. The time from the beginning of the development of ancient apes in the direction of humans is generally believed to be at least 10 million years ago. Quaternary marine invertebrates are still dominated by bivalves, gastropods, small foraminifera, and six-shot corals. Terrestrial invertebrates are still dominated by bivalves, gastropods, and mesomorphs. Other vertebrates continue to thrive with osteosaurs and birds, with little change in amphibians and reptiles. In the late Quaternary period, large terrestrial mammals underwent mass extinction. In North America, 70% of the genera of large mammals are extinct, and the proportion in Europe and Africa is much smaller. This mass extinction occurred between 15,000 and 9,000 years ago. The reason for the large-scale extinction is mainly human hunting activities, followed by changes in the natural environment. The Quaternary Great Glaciation Period, about 2 million years ago.
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