∞ generated and posted on 2016.11.06 ∞

Mammals that lack substantial placentas but nevertheless give birth to live if somewhat immature young.

Marsupials additionally are mostly associated with pouch within which these immature young are carried, protected, and where the marsupial teats are located, to which the marsupial infant are essentially permanently latched.

Most extant marsupials live in Australia as well as neighboring landmasses, such as the familiar kangaroo. A substantial number of additional marsupial species live in South America. Throughout much of North America there exists one marsupial species, the Virginia opossum.

A utility to being born so young is a relative ease by which offspring can be discarded by parents during bad times (e.g., drought or famines. A cost, however, is that the infant leaves the mother's body, or at least womb, in a somewhat vulnerable state.

An additional advantage, though, is that tethering of mothers to nests or burrows within which eggs are laid and offspring are nurtured can be eliminated through a combination of bearing of live young instead of laying eggs and then carrying those young within pouches where they are both mobile and protected.

Nonetheless, the marsupials are currently less successful than the eutherian (placental) mammals, and perhaps their relative lack of success can be tied to some degree to this marsupial reproductive strategy. Contrast also with monotremes.