Nondidelid

Nondidelid is a term used in marsupial taxonomy to describe marsupials that are not didelphids. Didelphids are the only family of marsupials native to the Americas, commonly known as opossums. Therefore, nondidelid refers to all marsupials outside of this family. This broad category encompasses the vast majority of marsupial diversity, found almost exclusively in Australasia.

The marsupial infraclass, Metatheria, is primarily divided into two major orders: Didelphimorphia, which contains the didelphids, and Dasyuromorphia, Peramelemorphia, Diprotodontia, and Notoryctemorphia, which together comprise the nondidelids. These nondidelid groups include a wide array of animals such as kangaroos, koalas, wombats, bandicoots, quolls, and Tasmanian devils.

The geographical distribution is a key distinguishing factor. While didelphids are strictly New World animals, their ancestors are believed to have originated in South America. The nondidelids, on the other hand, are predominantly found in Australia, New Guinea, and surrounding islands. Fossil evidence suggests that marsupials first evolved in the Northern Hemisphere and then migrated to South America, eventually dispersing to Australasia, where they diversified extensively in the absence of placental mammal competition. The term nondidelid, though descriptive, is less commonly used in formal scientific literature than discussions of specific marsupial orders and families.