Are Hippos Placental Mammals?

Are Hippos Placental Mammals? Unlike other mammals, placental mammals do much of their development in the womb. Just some examples of the more than 4,000 placental mammals are squirrels, hippos, and us! … These three groups are monotremes, marsupials, and the largest group, placental mammals. Monotremes are mammals that lay eggs. Are bats placental? Classification.