The mouths of Nile crocodiles are filled with 68 sharply pointed, cone-shaped teeth. The enlarged fourth lower tooth fits into the notch on the upper jaw and is visible when the jaws are closed.
The teeth of crocodiles are continually replaced as they wear. Beneath each visible tooth is a stack of replacements in various stages of development. When an old tooth is lost, the one under it grows into its place. A crocodile may go through as many as 3,000 teeth in its life.