Which group of mammals includes kangaroos, koalas, and wallabies?

Kangaroos, koalas, and wallabies are marsupials, mammals whose young are born at an unusually early stage of development and usually continue developing while attached to a teat, often inside a pouch.

Marsupials belong to the mammalian group Marsupialia. Their newborns are tiny and relatively undeveloped compared with newborn placental mammals. After birth, a young marsupial typically crawls to its mother’s pouch or nursing area, where it completes much of its early growth. The pouch is prominent in many species but is not identical in form across all marsupials.

Most living marsupial species are found in Australia and New Guinea, including kangaroos, wallabies, koalas, wombats, and Tasmanian devils. The Americas also have marsupials: opossums are the best-known examples. This means marsupials are not exclusively Australian animals.

Marsupials are commonly contrasted with placental mammals, whose embryos receive prolonged nourishment through a placenta before birth. Monotremes, such as the platypus and echidnas, form a third major mammalian lineage and lay eggs. The pouch is a useful clue, but the defining distinction is the marsupial reproductive strategy, not simply pouch ownership.