Ankle program
condylarthra
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Of species _
Mammalia mammalia
True mammals eutheria
The earliest insect fossils found in North America, mainly the west (the Rocky Mountain region) and Asia (mainly the Mongolian People's Republic) of the Lower Cretaceous (about one hundred million years). Fuxin, Liaoning, China Endo beast (endotherium), the times may be Late Jurassic or later, may be there is the earliest known placental fossils. The earliest primate fossils found in Montana (Late Cretaceous), ankle section of the first class are also found in the same layer.
Recently in South America (Argentina) found Cretaceous fossils similar to the purpose of poor teeth. The purpose of fossils in Asia (China and Mongolia) Paleocene also has found. These significant changes in the past on the origin and dissemination of the history of mammals hypothesis.
In the new generation of communication and distribution of mammals in North America and Asia, the Bering land bridge between the Bering Sea region (beringia), the Isthmus of Panama, the Indian subcontinent landmass in the Eocene (about 50 million years ago) with the "ancient Asian continent "and then hit" Ancient Mediterranean "(including Asian part; thethys sea) the disappearance (or south) and the Qinghai-Tibet Plateau uplift and so on, modern mammals (primarily real beast) in the distribution of the face, around the mammal fauna plays an important role in the composition.
True mammals, including extinct and extant placental mammals are, divided into 30 orders, the relationship between these objectives, or over the purpose of a unified opinion has not divided, but there are still some among these objectives more visible close genetic relationship. |