Didelphids, the family of marsupials of which the Virginia opossum (Didelphis virginiana) is the only living member, are the only marsupials left in North America. However, recent studies show that North America was once the hub of marsupial activity. In fact, the paradectids, a sister group to the didelphids, are now thought to have been the root of all living marsupials.
Compared with other mammals (except maybe monotremes such as the platypus), marsupials are remarkably primitive. They bear their undeveloped young in pouches, where the infants nurse until they are able to fend for themselves. Even their appearance is prehistoric, as any American with a trashcan can tell you from experience. They almost look as though they belong in the Mesozoic, rather than the modern day.
The news that these primitive mammals originated in North America has been decided based on a skull found in the Eocene Bighorn Basin of Wyoming, USA. Analysis of the skull, and two 30-million-year-old skeletons, shows that the split between opossums and all other marsupials on the planet occurred about 65 million years ago, at the end of the Cretaceous, in North America.
It is presently thought that marsupials migrated from North to South America until the end of the Cretaceous, when the two continents split (until the Pliocene, at least), and marsupials made their way through Antarctica to Australia, as the southern continent, much warmer in those days, is thought to have connected South America and Australia.
Compared with other mammals (except maybe monotremes such as the platypus), marsupials are remarkably primitive. They bear their undeveloped young in pouches, where the infants nurse until they are able to fend for themselves. Even their appearance is prehistoric, as any American with a trashcan can tell you from experience. They almost look as though they belong in the Mesozoic, rather than the modern day.
The news that these primitive mammals originated in North America has been decided based on a skull found in the Eocene Bighorn Basin of Wyoming, USA. Analysis of the skull, and two 30-million-year-old skeletons, shows that the split between opossums and all other marsupials on the planet occurred about 65 million years ago, at the end of the Cretaceous, in North America.
It is presently thought that marsupials migrated from North to South America until the end of the Cretaceous, when the two continents split (until the Pliocene, at least), and marsupials made their way through Antarctica to Australia, as the southern continent, much warmer in those days, is thought to have connected South America and Australia.
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