Marsupial

Marsupials are an infraclass of mammals living primarily in Australasia and the Americas. A distinctive characteristic, common to many species, is that most of the young are carried in a pouch. Well-known marsupials include kangaroos, wallabies, the koala, possums, opossums, wombats and the Tasmanian devil. Other marsupials include the numbat, bandicoots, bettongs, the bilby, quolls, and the quokka.

Marsupials represent the clade originating with the last common ancestor of extant metatherians. Like other mammals in the Metatheria, they are characterized by giving birth to relatively undeveloped young, often residing in a pouch with the mother for a certain time after birth. Close to 70% of the 334 extant species occur in the Australian continent (the mainland, Tasmania, New Guinea and nearby islands) with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central America, and one in North America north of Mexico.

Taxonomy

Taxonomically, the two primary divisions of Marsupialia traditionally are: American marsupials and the Australian marsupials. However, 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 the Australian marsupials. There are many small arboreal species in each group. The term 'opossums' is properly used to refer to the American species (though 'possum' is a common diminutive), while similar Australian species are properly called 'possums'. Similarly, shrew opossums are more closely related to australidelphians than to true opossums.