page_title: Alligatoridae
section_title: Phylogeny
hierarchical_section_title: Alligatoridae / Phylogeny
caption_attribution_description: Skeleton of Alligator prenasalis, a fossil gator
context_page_description: The family Alligatoridae of crocodylians includes alligators and caimans.
context_section_description: 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.
  This superfamily is thought to have split from the crocodile-gharial lineage in the late Cretaceous, about 87 million years ago. Leidyosuchus of Alberta is the earliest known genus. Fossil alligatoroids have been found throughout Eurasia as land bridges across both the North Atlantic and the Bering Strait have connected North America to Eurasia during the Cretaceous, Paleogene, and Neogene periods. Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million to about 65 million years ago) and the latter reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period. The Chinese alligator split from the American alligator about 33 million years ago and likely descended from a lineage that crossed the Bering land bridge during the Neogene. The modern American alligator is well represented in the fossil record of the Pleistocene. The alligator's full mitochondrial genome was sequenced in the 1990s and it suggests the animal evolved at a rate similar to mammals and greater than birds and most cold-blooded vertebrates. The full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.
caption: Alligator prenasalis fossil
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