The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator than to either the Nile crocodile or the gharial.

Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million[8] to about 65 million years ago[7]) and the latter reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period.

In Central and South America, the alligator family is represented by six species of the subfamily Caimaninae, which differ from the alligator by the absence of a bony septum between the nostrils, and having ventral armour composed of overlapping bony scutes, each of which is formed of two parts united by a suture.

[13] C. crocodilus, the spectacled caiman, has the widest distribution, from southern Mexico to the northern half of Argentina, and grows to a modest size of about 2.2 m (7.2 ft).

The largest is the near-threatened Melanosuchus niger, the jacaré-açu or large or black caiman of the Amazon River basin.