Crocodiles and Alligators belong to the Order Crocodilia which is a large order of reptiles that have been around for approximately 84 million years. Crocodiles are the closest living relatives to birds.
The following lists the current families of Crocodilians.
Family Gavialidae: Gharials and False Gharials
Family Alligatorinae: Alligators
Family Crocodylinae: Crocodiles