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Mammals
Marsupials
Opossums

What type of mammal is a marsupial?

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April 01, 2013 5:11AM

A marsupial is often described as a pouched mammal, but this is not necessarily what defines it.

Marsupial young are born very undeveloped. Moving purely by instinct, the baby joey (the term for all marsupial young) makes its way to the mother's pouch, where the young joey latches onto a teat, remaining there to continue its growth and development.

Many marsupials have the mammary glands enclosed within a protective pouch. Although a mammal with a pouch is always a marsupial (with the exception of the echidna, which develops a rudimentary pouch during breeding season), not all marsupials have pouches, for example, the numbat of Western Australia.

All marsupials are mammals, but not all mammals are marsupials. Marsupials do not have advanced placentas, and have epipubic bones (with the exception of the marsupial mole). Epipubic bones are bones which project forwards from the pelvis. In the case of marsupials, these bones support the female's pouch, but there are other mammals which are not marsupials which also have epipubic bones. The excretory and reproductive systems of placental mammals and marsupials are also different.

Female marsupials have two vaginas, or what are called paired lateral vaginae. These are for the purpose of transporting the sperm to the womb, but there is a midline pseudovaginal canal for actually giving birth. As well as two vaginas and two uteruses, female marsupials have two fallopian tubes and two cervixes. Most male marsupials, with the exception of the largest species, the Red Kangaroo, Eastern Grey and Western Grey Kangaroos and one of the smallest species, the Honey Possum, have a two-pronged penis to accommodate the females' two vaginas.