marsupials did not originate in Australia, but probably arrived in Australia from South America via the South Pole before Gondwana was separated. However, due to the lack of competition from placental species in Australia, marsupials flourished in Australia. Marsupials include some of the most familiar Australian animals, and koalas and kangaroos have almost become symbols of Australia. In prehistoric South America, marsupials occupied the ecological position of carnivores and insectivores, while in Australia, they occupied almost every niche of mammals and became the dominant animals in Australia, and evolved into different types corresponding to different true mammals in other continents, from small insectivores to large herbivores < P > Metatheria, and Marsupialia

Marsupialia is marsupialia, so there is no real placenta. This reproductive habit may not be unique to the post-theropoda, but has been produced among the members of the early theropoda. Marsupials first appeared in North America in the middle Cretaceous. They are small carnivorous and insect-eating animals similar to modern opossums. They have flourished in North America in the late Cretaceous and entered other continents. In the Cenozoic era, marsupials in most areas were extinct due to the competition of true mammals, while marsupials in Antarctica were extinct due to the formation of ice sheets, and only in Oceania and South America were they preserved and flourished. /swtd/dongwu/jzdwm/frdwm5.htm

Australia includes all parts of Oceania and is one of the two smallest zoogeographical regions. Australia was originally a part of Gondwana. It was separated from other continents a long time ago and isolated from other continents for a long time. It is the most independent among all walks of life. The animals in Australia are mainly descendants of primitive animals in Gondwana and many unique types that have developed independently, so Australia is also known for its most unique species. There are only a few representative mammals in Australia, and the most representative mammals are monotremes and marsupials.

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