Why is a platypus a mammal?

Animals are so interesting because they don't always follow the rules. Some mammals lay eggs; some snakes give birth to live young. Birds are in fact the only class of vertebrates that reproduce solely by laying eggs. read more

ANSWER: Believe it or not, platypuses are not the only mammals that lay eggs. Mammals that lay eggs are called monotremes and include platypuses and echidnas, both of which live in Australia. read more

The platypus (Ornithorhynchus anatinus), sometimes referred to as the duck-billed platypus, is a semiaquatic egg-laying mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young. read more

The platypus is among nature's most unlikely animals. In fact, the first scientists to examine a specimen believed they were the victims of a hoax. The animal is best described as a hodgepodge of more familiar species: the duck (bill and webbed feet), beaver (tail), and otter (body and fur). Males are also venomous. read more

Monotreme mammals like the modern echidna and platypus kept this trait when their family branch split off of the mammal family tree. It is the oldest style of mammal birth. The next newest branch to split off were the marsupial mammals. read more