Do you know that Marsupials are the result of premature births?

They continue to develop outside the womb. The young remain attached to the mother’s teats for a period corresponding to the late stages of fetal development of a placental mammal.
More than 170 species including bandicoots, kangaroos, koalas, wombats are found in Australia, New Guinea, and nearby islands.
Most species have a pouch, a fold of skin covering the nipples on the mother’s lower belly, where the young continue their development.
Brushtail Possum Joey suckling in pouch