Crocodilia

Crocodilia is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria.

Taxonomy

The order Crocodilia includes the true crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae), and the gharial and false gharial (family Gavialidae). Although the term 'crocodiles' is sometimes used to refer to all of these, a less ambiguous vernacular term is crocodilians.

Anatomy and Physiology

Crocodilians are more closely related to birds and dinosaurs than to most animals classified as reptiles. They have a four-chambered heart, diapsid skull, and other physical traits shared with birds.

Behavior

Crocodilians are complex, sophisticated creatures that have a wide range of behaviors. They are social creatures that communicate with a variety of sounds, postures, and behaviors.

Conservation

Many species of crocodilians are at the risk of extinction, some being classified as critically endangered.

See Also

• Crocodylidae
• Alligatoridae
• Gavialidae

References

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Crocodilia

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