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What's the Difference Between Alligators and Crocodiles?

american alligator, american crocodile, differences
Close inspection (Image credit: National Park Service photos by Rodney Cammauf.)

Coming face to face with a crocodile or an alligator, you'd see a mouth full of serrated teeth that would likely scare the bejeezus out of you.

The two reptile groups are close relatives, so their physical similarities are expected.

Upon closer inspection, not recommended out in the wild, you'd spot glaring differences:

  • Snout shape: Alligators have wider, U-shaped snouts, while crocodile front ends are more pointed and V-shaped.
  • Toothy grin: When their snouts are shut, crocodiles look like they're flashing a toothy grin, as the fourth tooth on each side of the lower jaw sticks up over the upper lip. For alligators, the upper jaw is wider than the lower one, so when they close their mouths, all their teeth are hidden.
  • Home base: Crocodiles tend to live in saltwater habitats, while alligators hang out in freshwater marshes and lakes.

They belong to the subgroup Eusuchia, which includes about 22 species divided into three families: the fish-eating gavials or gharials, which belong to the Gavialidae; today's crocodiles or the Crocodylidae; and the Alligatoridae, or alligators. Eusuchians appeared on the scene during the late Cretaceous some 100 million or so years ago.

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Jeanna Bryner

Jeanna is the editor-in-chief of Live Science. Prior to this role, she served as the site's managing editor, and before that a reporter for both Live Science and Space.com. Previously she was an assistant editor at Scholastic's Science World magazine. Jeanna has an English degree from Salisbury University, a Master's degree in biogeochemistry and environmental sciences from the University of Maryland, and a science journalism degree from New York University.