How does a Platypus give birth?

The unique nature of the curiously constructed platypus starts even before birth and marches on from there.

The platypus is a monotreme--a group where the females produce offspring by laying eggs. Giving birth this way is extremely unusual among living mammals--but normal for most other animals. Almost every other vertebrate, including most reptiles, amphibians, fish, and birds, reproduces by laying eggs.

Along stretches of its native rivers in eastern Australia, the female platypus digs a burrow near a stream and fills it with soft leaves as a place to lay eggs. Platypus babies cut their way out of the egg using a sharp "egg tooth" --a horny spike on the nose that is made of keratin, the same material as fingernails, that later falls off.