A platypus is one of the strangest animals on Earth: a mammal that lays eggs, has a duck-like bill, webbed feet, and a beaver-like tail. Found only in eastern Australia, platypuses live in rivers and streams, where they hunt underwater for insects, worms, and small crayfish.

What makes the platypus so bizarre is that it combines features that don't usually go together. Most mammals give birth to live babies, but the platypus lays eggs like a bird or reptile. It's covered in waterproof fur, yet it has a rubbery bill instead of a snout. Male platypuses even have venomous spurs on their hind legs, powerful enough to cause severe pain (though not deadly to humans).

When European scientists first examined a platypus specimen in 1798, many thought it was a hoax, like someone had sewn different animals together as a joke. But the platypus is completely real. It's one of only five surviving species of monotremes, an ancient group of mammals that split from other mammals over 100 million years ago.