The platypus (Ornithorhynchus anatinus), with its duck bill and webbed feet, is a unique Australian animal. It and the two species of echidna are the only monotremes or egg-laying mammals to be found on earth. The marsupials (mammals with pouches, e.g. kangaroos) and eutherians (placental mammals that give birth to well developed young, e.g. humans) both give birth to live young. The monotremes have lower body temperatures than other mammals and have legs which extend out, then vertically below them. These features together with their egg-laying are more like that of a lizard than a mammal.