Evolution of marsupials
| Marsupials Temporal range: Paleocene – Holocene, 65–0 Ma |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Clade: | Metatheria |
| Infraclass: |
Marsupialia Illiger, 1811 |
| Orders | |
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| Present-day distribution of marsupials. | |
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia and the Americas. A distinctive characteristic common to these species is that most of the young are carried in a pouch. Well-known marsupials include kangaroos, wallabies, koalas, possums, opossums, wombats, and Tasmanian devils. Some lesser-known marsupials are the potoroo and the quokka.
Marsupials represent the clade originating from the last common ancestor of extant metatherians. Like other mammals in the Metatheria, they give birth to relatively undeveloped young that often reside in a pouch located on their mothers’ abdomen for a certain amount of time. Close to 70% of the 334 extant species occur on the Australian continent (the mainland, Tasmania, New Guinea and nearby islands). The remaining 100 are found in the Americas — primarily in South America, but thirteen in Central America, and one in North America, north of Mexico.
Taxonomically, the two primary divisions of Marsupialia are American marsupials (Ameridelphia) and Australian marsupials (Australidelphia). The order Microbiotheria (which has only one species, the monito del monte) is found in South America, but is believed to be more closely related to Australian marsupials. DNA evidence supports a South American origin for marsupials, with Australian marsupials arising from a single Gondwanan migration of marsupials from South America to Australia. There are many small arboreal species in each group. The term "opossum" is used to refer to American species (though "possum" is a common diminutive), while similar Australian species are properly called "possums".
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Wikipedia