Alligatorinae is a subfamily within the family Alligatoridae that contains the alligators and their closest extinct relatives, and is the sister taxon to Caimaninae (the caimans). Many genus in Alligatorinae are described, but only the genus Alligator is extant, with the remaining being extinct.
Evolution
Alligators and
caimans split in North America during the early
Tertiary period or late
Cretaceous (about 53 million to about 65 million years ago).
The Chinese alligator split from the American alligator about 33 million years ago
and likely descended from a lineage that crossed
Beringia 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.
The full
genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.
Phylogeny
Alligatorinae is
Cladistics defined as
Alligator mississippiensis (the American alligator) and all species closer to it than to
Caiman crocodylus (the spectacled caiman).
This is a
stem-based taxon definition for Alligatorinae, and means that it includes more basal
extinct alligator ancestors that are more closely related to living alligators than to
caimans.
The below cladogram shows the phylogeny of Alligatorinae.[
]
