乐生活As early as about 410 million years ago in the early Silurian, the earliest spokefin fish in the world appeared on the earth. But now, all the orders of spokefin fish on the earth come from the Mesozoic and Cenozoic after the Paleozoic. The oldest group is no more than 200 million years ago.
This phenomenon is due to the 186 million years of the Mesozoic. When the terrible Permian-Triassic extinction ended and the history of the Earth entered the Mesozoic, the ancient Spokefin fishes from the Paleozoic were still flourishing, but with the rapid development of more progressive groups, they also declined rapidly.
In the Paleozoic, except for Acentroporus and some very early species of the subosseous class, all spokefin fishes were called "cods". Cod is often cartilaginous, hard-scaled fish with a high diversity, including several orders, from the Silurian to the end of the Mesozoic.
Before the end of the Cretaceous, all the cods were extinct, but their two offspring continued. They evolved from the late Paleozoic and Mesozoic respectively, the former being spokefins and the latter being multifins.
In a sense, Polypterus is actually a cod. They are very primitive. They are an independent branch of COD produced in the later stage of evolution. They do not make up a single branch with other existing spotted fin fishes. Scanilepiformes, an ancient cod that lived in the Triassic period, is now considered the closest fish to the multifin fish.
Late Permian invertebrate fish are the only Paleozoic radial fins known to us. At that time, dinosaurs did not appear. Dry and cold land was the world of synarchs, and all kinds of ancient cods swam in the waters of the world. After the extinction, the vertebrate-lacking fish continued to the Triassic, and other radial fins began to flourish at this time. Fossil records emerged in large numbers. Various radial fins quickly filled into the water ecosystems of the earth, and a new era began.
But Paleozoic radial fins are obviously not the only genus of Vertebrate-deficient fish. The separation of bony fish, cartilaginous scaly fish and other radial fin fishes from Vertebrate-deficient fish can be traced back to a more distant period, but the corresponding fossils have not yet been found. At that time, the radial fins had just started, and they did not have any advantage over other fish. But soon after the Permian-Triassic extinction swept the earth, the radial fins rose to the ground and became the most abundant fish on the planet.
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I don’t know if I can understand this article. Let’s put some pictures.
1. Acentroporus varians, a vertebral-lacking fish. The subosseous class of vertebrate-deficient fish is the dominant fish of the Mesozoic, but it has declined now. At present, there are only two orders, two families and less than ten species of whole-bone fish, namely archfin fish and several species of sparrow eel.
2. Tarrasius problematicus, an eel cod. Eel cod is a Carboniferous ancient cod with an eel-like body. The skeleton of eel cod is similar to that of tetrapods, so it was previously thought to be a tetrapod fin fish.
3. Cheirolepis, a Devonian cod, is also in a very basic position in the COD family.
4. Paranaichthys, long-horned cod
5. Dorypterus, a Permian cod
6. Guildayichthys carnegiei belongs to the Carboniferous Gildae, one of the cods. Gildae was previously thought to be a close relative of multifin fishes, but it has little to do with it at present.
7. Restoration of Kashi Gilderfish
8. Fukangichthys longidorsalis, a member of the Scandinavian Fish Family, was found in Xinjiang.
9. Polypterus endlicherii
