small densely furred aquatic monotreme of Australia and Tasmania having a broad bill and tail and webbed feet; only species in the family Ornithorhynchidae
A semi-aquatic, egg-laying monotreme mammal with a bill resembling that of a duck, that has a mole-like body, a tail resembling that of a beaver, a waterproof pelt, and flat webbed feet — males have poisonous spurs on the inside of the back legs; Ornithorhynchus anatinus