As nouns the difference between platypus and otter
is that platypus
is an egg-laying, semi-aquatic 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
otter is any aquatic or marine carnivorous mammal, member of the family Mustelidae
, which also includes weasels, polecats, badgers, and others.
As a proper noun Otter is
a river whose source in the Blackdown Hills, Somerset, and which flows into Lyme Bay in English Channel.