Alligators, along with other crocodilians, were among the few reptiles to survive the mass extinction that killed nearly all dinosaurs and marine life 65 million years ago. In fact, crocodilians and birds are the sole survivors of a much larger and more diverse group called the archosaurs.

There is debate over exactly when alligators evolved from crocodiles, but fossils show that both of these families have gone virtually unchanged since the Late Cretaceous.

One way you can tell alligators from crocodiles is by their teeth. An alligator’s lower teeth fit into sockets in the upper jaw and remain completely hidden when their mouth is closed. A crocodile’s lower teeth are exposed on the outside of the upper jaw when their mouth is closed.

These teeth were legally purchased from a licensed alligator farm.