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Statistical results vary greatly in different works at different times. According to the recently published "Encyclopedia of Vertebrates of China" and the "Zoology of China", which is being compiled and printed, there are 1050 species of fish distributed in China's freshwater (including coastal estuaries), belonging to 18 orders, 52 families and 294 genera. Among them, there are 967 species of pure freshwater fish, 15 species of migratory fish in haihe rivers, and 68 species of estuarine fish. Among these 1050 species of fish, they can be roughly divided into the following four categories:
1, round mouth class: this type of fish is the most primitive fish-shaped vertebrate. There is no real upper and lower jaw in the mouth of the fish, the mouthparts form suction cups, and they live a parasitic or semi-parasitic life. There is no real spine on the body, only the cord. From the evolutionary period, the round mouth class first appeared in the Middle Ordovician, most developed in the Silurian and Lower Devonian periods, and gradually disappeared from the Lower Devonian Period, and only a few species remain to this day. In China's freshwater, only three species of lamprey eels live in the rivers from Heilongjiang to Liaohe in the northeast region.
2. Cartilaginous fish: Cartilaginous fish were found in the Upper Devonian Period, most developed in the Carboniferous Period, and continued to evolve to become modern sharks and rays. The whole body of these fish is cartilage, the scales are small shield scales, and there are spiral valves in the intestine. This is a group of low-level real fish, almost all of the living cartilaginous fish live in the ocean, only a few species live in fresh water, of which the red stingray in addition to a large number of living in the ocean, there is a small group settled in China's Guangxi Nanning to Longzhou Xijiang river system ZuoJiang, from its evolutionary history, red stingray is a marine fish. According to ancient geological research, Guangxi was originally a sea, due to the orogeny of the earth's crust, all in the Cenozoic Period in the Tertiary Period at the end of the Pliocene, when the sea water withdrew from Guangxi and was "land sealed" settled in the inland water body.
3. Cartilaginous scleros: This type of fish is a teleost fish, but the bone system is cartilaginous. The body surface scales appear as bony diamond-shaped primitive scales with a crooked caudal fin and spiral flaps in the intestine. Primitive cartilaginous scaly fish appeared in the Devonian period and survived on Earth for quite a long time, until most species extinct in the Mesozoic Era. The living sturgeon appeared in the Cretaceous Period, and there are not many species that survive now, only distributed in the high-latitude Arctic Ocean region, and one species of the white sturgeon family and 2 genera and 8 species of the sturgeon family live in freshwater in China.
4, true bone fish: this is the common habit of living, real fish, for the most prosperous fish in modern times, China's one thousand and fifty other freshwater fish, except for a few species (13 species), almost all belong to the bone fish. China's freshwater fish are mainly cyprinids, especially carps account for about half of the total. Among them, there are 5 species in 3 genera of 1 family of herring, 32 species in 17 genera of 6 families of tuna, 2 species in 1 genus of 1 family of eels, 740 species in 170 genera of 6 families of Cyprinids, 10 species of 27 genera and 110 species of cyprinids, 4 species in 3 genera of 2 families of medaka, 4 species in 1 genus of 1 family of jaw needles, 1 genus and 1 species of 1 family of quartz, 2 species of 2 genera of 1 family of trouts, 7 species of 3 genera of 1 family of trout, 1 family of 1 family of zygotes, 110 species of 510 species of 12 families of perch, 4 genera of 1 family of 1 family of perch, 8 species of 4 genera of 1 family of quail, 3 genera of 3 families of quail, 3 genera of 3 families of quail, 510 species of perch family, 8 species of 3 genera of 3 families of quail, and 3 genera of 3 families of quail. There are 6 species in 2 genera and 1 family of 1 family, with a total of 1037 species in 15 orders and 49 families.
Eukeletal fish appeared in the Jurassic Period, and during the Cretaceous Period, the morphological structure of the ancient eukeletal fish evolved into modern eukeletal fish. The upper and lower jaws of the skull are generally shortened, the superior type of maxilla is specialized as a bone rod without teeth, the teeth are concentrated on the premaxilla, the caudal fin becomes a fully symmetrical tail or orthogonal tail, the inner bone is highly ossified, the odd and even fins show a variety of shapes, and the ventral fin is often moved from the abdomen to the head, and the scales become very thin and round.
The internal and external structures of the bony fish have a perfect aquatic adaptation structure, starting from the Cretaceous Period, along many radiation adaptation routes, making them a living being in all the waters on the earth's surface.
(Source: China Science Expo)
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