Alligatoroidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, alligatoroidea is Alligator mississippiensis (the American alligator) and all crocodylians more closely related to A. mississippiensis than to either Crocodylus niloticus (the Nile crocodile) or Gavialis gangeticus (the gharial).