Eutheria belongs toMammaliaEutheria Animals, including monotremes, marsupials and extinct primitive animalsGnarled mammal、Shu mammalsAll other placental mammals are the dominant animals on the modern earth, which are divided into about 30 orders, including the primates to which humans belong and some completely extinct orders.
Eutheria includes monotremes, marsupials and extinct primitive animalsGnarled mammalAll placental mammals except Shu mammals are the dominant animals on the modern earth, which can be divided into about 30 orders, including the primates to which humans belong and some completely extinct orders.In addition to the special group of primates, the most basic and important of all living and fossil placentas are insec tivora andCondylarthra (condylarthra)。Insectivores may include the ancestors of small mammals such as primates, carnivores and bats.Ankle program is a completely extinct order, and almost all living and extinct ungulates mammals may be derived from this order.Whales and other marine mammals may come from the ancestors of ancient carnivores.
Development history
Announce
edit
The earliest insectivorous fossils were mainly found in the Lower Cretaceous (about 100 million years ago) in western North America (Rocky Mountains region) and Asia (mainly the People's Republic of Mongolia).Fuxin, Liaoning, ChinaEndotherium The age may be Late Jurassic or later, and it may be the earliest known fossil with placentas.The earliest primate fossils were found in Montana (Late Cretaceous) in the United States, and the earliest ankle arthropods were also found in the same horizon.
About 65 million years ago, at the end of the Cretaceous Period, dinosaurs and many reptiles were extinct, including placentas or real animals, which developed rapidly on the basis of insect eaters and ankle programs.At the beginning of the Paleocene (65 million years ago), not only a large number of small carnivores and carnivores appeared, but also several large ungulates, which replaced some extinct Mesozoic reptiles and occupied their empty habitats.This is the second and most rapid differentiation in the history of mammals after their emergence.From the ankle program, especially from thePseudoodontidae(phenacodontidae), which developed the early order of odd hoofed and even hoofed, possibly the long nose and several completely extinctarchaic ungulata 。The most widely distributed fossils arePanodonta(pantodonta) and dinocerata, whose small bodies are similar to foxes and dogs, and large ones are similar to cattle orHippo。
Recently, fossils of approximate anodonta have been found in the Cretaceous of South America (Argentina).Fossils of this order have also been found in the Paleocene in Asia (Guangdong, China and Mongolia).These have greatly changed the past hypothesis about the origin and spread history of mammals.
In terms of the spread and distribution of Cenozoic mammals, the Beringia land bridge in the Bering Sea area between North America and AsiaIsthmus of PanamaIn the Eocene (about 50 million years ago), the Indian subcontinent collided with the "ancient Asian continent", the "ancient Mediterranean" (including the Asian part; the sea) disappeared (or moved southward), and the uplift of the Qinghai Tibet Plateau played an important role in the distribution of mammals (mainly true mammals) in modern times, and the composition of mammalian fauna in various regions.
Euzoa includes extinct and living placental mammals, which are divided into more than 30 orders. There is no unified opinion on the relationship between these orders or the division of super orders, but there are still some obvious close relatives between these orders.
