As we all know, the Australian continent is a utopia of marsupials, where there live a large number of kangaroos, koalas, tasmanian devils, wombats and other nearly 260 species of marsupials.
Many people think that these marsupials originated in Australia, but scientists have found that the vast majority of marsupials did not live in Australia all the time, but gradually migrated to this place.
Marsupials are a very important and ancient part of mammals, and they are very different from today's placental mammals, such as cattle, sheep, monkeys and other mammals, all of which have placenta at birth, while marsupials do not have a placenta at birth.
The placenta plays a very important role in the development of mammalian fetuses, as an important organ to protect the embryo from the attack of the maternal immune system, because the protection of the placenta is missing, so the fetus of marsupials has no way to complete the development in the mother's body, and when it is just born, everyone is a veritable premature baby.
So these newborn marsupial pups need to enter the mother's pouch on their own and continue to grow in the pouch, and these pups need to stay in the pouch for several months.
Cubs like kangaroos are born like the size of a soybean, and adult kangaroos can weigh up to hundreds of pounds.
These cubs are not fully developed by their organs at birth, and can only rely on their own intuition, like worms along the hairs on the mother's belly, using their tongues to lick out a passage into the nursery bag to live, until half a year later, they will begin to live independently.
But these marsupials are not native to Australia, so where did they come from?
Scientists have found through research that the progenitor of marsupial mammals came from the North American continent, and in the Cretaceous Period 120 million years ago, a small number of mammals evolved a placenta, which is contrary to the evolutionary path of marsupials, which gradually evolved into even-hoofed animals, rodents, pterodactyls, and marsupials took a different path.
These ancient marsupials evolved at least 20 species on the North American continent today, but for some special reason, 66 million years ago, marsupials began to migrate south and live on the South American continent, and dinosaurs were extinct in the same period, but how marsupials survived is still a mystery.
At that time, North and South America were not as interconnected as they are today, and the nearby Continents were connected by road bridges and several islands, so these surviving marsupials were able to come to South America from North America.
Marsupials that entered the South American continent immediately began to breed, they were mixed with local close relatives, and over the course of millions of years, they gradually evolved a wide variety of marsupials.
Some of these marsupials are large, as strong as rhinoceros, some are as small as rats, some have become carnivores, evolving sharp fangs and claws, and some have become vegetarians, this multi-ecological evolutionary strategy has allowed marsupials to replace the ecological supremacy of placental mammals.
For millions of years, although many animals have become extinct in South America, some marsupials have survived, and today, hundreds of Species of Possums and other Marsupials live in South America.
South American possum and Australian possum is not the same animal, Australian possum is a special species native to Australia and New Guinea, closer to the kangaroo on the evolutionary road, and south American possum in the body structure and habits there are great differences, so the Australian possum is not followed by Homo sapiens to Australia South American possum offspring.
So how did marsupials migrate from the Americas to Australia?
More than 40 million years ago, the Antarctic continent did not move to its current position, it connected North and South America and the Australian continent, at that time on the Antarctic continent, there were many temperate rainforests, such environmental advantages, attracted many marsupials into the Antarctic continent to live.
These marsupials gradually went all the way south, across the Antarctic continent, and finally settled in Australia, and scientists have also found fossils of marsupials and related species on Seymour Island on the Antarctic continent, which also proves that the Antarctic continent once lived marsupials.
Scientists have found 55 million-year-old fossils of ancient marsupials in Australia, which are similar to the fossils of marsupials found in South America, which also shows that marsupials on both continents share a common ancestor.
However, in Australia, the record of marsupial fossils appeared a gap period of 30 million years ago, and 25 million years ago, a large number of marsupials gradually appeared in Australia, and biodiversity began to be enriched, and gradually there were close relatives of koalas, wombats, kangaroos, tasmanian devils, thylacines, kangaroos and other animals.
But how these marsupials survived five mass extinctions in Australia remains a mystery. From North America to South America, to the Antarctic continent, and finally to Australia, marsupial habitats have changed dramatically.
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