Marsupials differ from placental mammals in their reproductive traits.
In Australia, placental mammals were not present throughout much of the Tertiary and marsupials and monotremes dominated completely.
Many marsupials resemble familiar placental species, including the wombat resembling a groundhog; the glider, a flying squirrel; the marsupial mole, a placental mole; and the cuscus, a monkey (Mayr 2001, Towle 1989).
Nonetheless, many extant marsupials resemble placentals in appearance.
Marsupials are one of three groups of mammals, the others being monotremes and placental Mammals.
Well-known marsupials include kangaroos, opossums, bandicoots, wombats, and the flying phalanger.
The early birth of marsupials removes the developing young much sooner than in placental mammals, and marsupials have not needed to develop a complex placenta to protect the young from its mother's immune system.
Marsupials are native to Australia, New Guinea, Tasmania, and the Americas.
Marsupials are non-placental mammals belonging to the infraclass (or order) Marsupialia.
Some marsupials have a rudimentary placenta that functions for only a short time, such as the bandicoot.
Marsupials have a cloaca (posterior opening that serves as the only such opening for the intestinal and urinary tracts) that is connected to a urogenital sac in both sexes.