While placental mammals and marsupials share some traits, the way they reproduce is different. For example, placental mammals give birth to developed young, while marsupials’ young are extremely underdeveloped and must spend time developing in their mother’s pouch. Moreover, the amount of time spent suckling is much longer in marsupials compared to placental mammals. The reproductive systems of the two also differ somewhat, with marsupials having pairs of organs, including two vaginas and two uteruses.