marsupial

A marsupial is a mammal belonging to the infraclass Metatheria. Unlike placental mammals, most marsupials give birth to relatively undeveloped young that complete their development after birth, often in a pouch on the mother's abdomen. The pouch contains teats to feed the developing offspring. Some species have a permanent pouch; others lack a true pouch, and the young finish development after birth while nursing from a nipple.

Marsupials are most diverse in Australia and nearby islands, with a smaller assemblage in the Americas. The Australian region includes kangaroos, wallabies, koalas, wombats, and possums; in the Americas, opossums and several smaller taxa occur. Marsupials vary in size from the tiny planigale to the red kangaroo, and their diets range from herbivory and omnivory to insectivory and carnivory in a few species. They occupy a broad range of habitats, from forests and grasslands to deserts and urban areas.

In reproductive terms, many marsupials have a short gestation and give birth to tiny, altricial young that migrate to the pouch and attach to a nipple to finish development. Some species delay the establishment of an embryo, a form of diapause, allowing continued reproduction. The diversity of dental and skeletal features reflects their long evolutionary history, which began in Gondwanan landmasses and subsequently diversified in Australia before some lineages spread to the Americas.

Conservation status varies: several species are threatened by habitat loss, introduced predators, and disease, and island populations are especially vulnerable.