An order of subclass Theria of class Mammalia, Phylum Chordata, Kingdom Animalia. There are over 260 species of marsupials. The six major groups of marsupials are:

• Didelphid (opossum, etc.)
• Caenolestid (rat opossum, etc.)
• Phalanger (possum, cuscus, etc.)
• Dasyurid (native cat, tasmanian devil, etc.)
• Peramelid (bandicoot, etc.)
• Macropod (kangaroo, etc.)

Koalas and wombats do not fit into one specific group.

Sources:
http://urbania.kcizone.com/marsupials/
http://www.geocities.com/RainForest/9971/chordat.htm

Mar*su`pi*a"li*a (?), n. pl. [NL., fr. L. marsupium a pouch, bag, purse, Gr. , dim. of , .] Zool.

A subclass of Mammalia, including nearly all the mammals of Australia and the adjacent islands, together with the opossums of America. They differ from ordinary mammals in having the corpus callosum very small, in being implacental, and in having their young born while very immature. The female generally carries the young for some time after birth in an external pouch, or marsupium. Called also Marsupiata.

 

© Webster 1913.