Merriam-Webster Collegiate Dictionary - platypus

 noun  (plural ~es; also platypi)  Etymology: New Latin, from Greek platypous flat-footed, from platys broad, flat + pous foot — more at place, foot  Date: 1799 a small carnivorous aquatic monotreme mammal (Ornithorhynchus anatinus) of eastern Australia and Tasmania that has a fleshy bill resembling that of a duck, dense fur, webbed feet, and a broad flattened tail — called also duck-billed ~