Answer:
A platypus is a mammal that lays eggs - a monotreme. It is one of only two mammals known to do so, the other being the echidna. The eggs are soft-shelled and leathery, rather than hard-shelled like birds' eggs.
It is a semiaquatic egg-laying mammal (Ornithorhynchus anatinus) of Australia, having a broad flat tail, webbed feet, and a snout resembling a duck's bill.