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The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile endemic to the southeastern United States. It is one of two living species in the genus ''Alligator'' within the family Alligatoridae; it is larger than the other extant alligator species, the Chinese alligator. Adult male American alligators measure up to in length, and can weigh up to . Females are smaller, measuring around . The American alligator inhabits freshwater wetlands, such as marshes and cypress swamps from Texas to North Carolina. It is distinguished from the sympatric American crocodile by its broader snout, with overlapping jaws and darker coloration, and is less tolerant of saltwater but more tolerant of cooler climates than the American crocodile, which is found only in tropical climates. Alligators are apex predators and consume fish, amphibians, reptiles, birds, and mammals. Hatchlings feed mostly on invertebrates. They play an important role as ecosystem engineers in wetland ecosystems through the creation of alligator holes, which provide both wet and dry habitats for other organisms. Throughout the year, but particularly during the breeding season, alligators bellow to declare territory and locate suitable mates. Male alligators use infrasound to attract females. Eggs are laid in a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water. Young are born with yellow bands around their bodies and are protected by their mother for up to one year. The American alligator is listed as Least Concern by the International Union for Conservation of Nature. Historically, hunting had decimated their population, and the American alligator was listed as an endangered species by the Endangered Species Act of 1973. Subsequent conservation efforts have allowed their numbers to increase and the species was removed from the list in 1987. Alligators are now harvested for their skins and meat. The species is the official state reptile of three states: Florida, Louisiana, and Mississippi. ==Taxonomy and phylogeny== The American alligator was first classified by French zoologist François Marie Daudin as ''Crocodilus mississipiensis'' in 1801. In 1807 Georges Cuvier created the genus ''Alligator'';〔url=http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=174366#〕 the American alligator shares this genus with the Chinese alligator. They are grouped in the family Alligatoridae with the caimans. 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. Members of this superfamily first arose in the late Cretaceous. ''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 late Cretaceous and the latter reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period. The Chinese alligator 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 other cold-blooded vertebrates. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「American alligator」の詳細全文を読む スポンサード リンク
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