An egg tooth is a hard, often sharp protuberance that is found on the snout of many babies that hatch from eggs. These help the babies escape from the egg when it's time, but they are not real teeth. Unlike real teeth, egg teeth will usually disappear a short time after birth. Bird and reptiles are two types of baby animals that have egg teeth when born.
Most egg-laying animals develop these type of teeth when they are in the egg. An egg tooth can usually be found on the nose or beak of an animal. Although it is tooth-like and quite hard, it is not a real tooth. Instead of being made from bone, an egg tooth is usually made from a hardened nub of skin.
As the baby grows, it becomes much harder for the animal get needed oxygen. After weeks or months in an egg, a hatchling must be able to get out quickly. It can be very difficult to do this, since many eggs have a hard or tough exterior. The egg tooth is then used as a tool to help break through this shell.
Birds develop an egg tooth while inside an egg. Along with this tooth, a baby bird also has a special muscle located in the back of its neck. This is often referred to as a pipping muscle.
When the hatchling has grown bigger and begins to have trouble getting oxygen, it will begin to use these special anatomical parts to break out of its shell. First, it will use its egg tooth, located on the end of its beak, to put a hole in the air sac on the inside of the egg. This will give the hatchling more oxygen, so it can begin to peck its way through the hard exterior of the shell. The egg tooth will then usually fall off within a few months.
Reptiles will also usually develop these teeth while inside their eggs. A reptile egg tooth will usually be on the animal's snout. Snakes, for example, use these teeth to cut through their leathery shells. After a snake's first shedding, the tooth will disappear.
A crocodile also develops an egg tooth before emerging from an egg. Crocodile eggs are different than most reptile eggs, since they are not leathery. Instead they have a hard exterior, like a bird's egg. A few months after a crocodile hatches, this hard piece of skin disappears.