Alligator. An alligator, or colloquially gator, is a large reptile in the Crocodilia order in the genus Alligator of the family Alligatoridae. The two extant species are the American alligator and the Chinese alligator. Additionally, several extinct species of alligator are known from fossil remains. Alligators first appeared during the Oligocene epoch about 37 million years ago. Alligators and caimans split in North America during the early Tertiary or late Cretaceous. The Chinese alligator split from the American alligator about 33 million years ago and probably 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. The full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds. The genus Alligator belongs to the subfamily Alligatorinae, which is the sister taxon to Caimaninae. Together, these two subfamilies form the family Alligatoridae. An average adult American alligator's weight and length is 360 kg and 4 m, but they sometimes grow to 4.4 m long and weigh over 450 kg. The largest ever recorded, found in Louisiana, measured 5.84 m. The Chinese alligator is smaller, rarely exceeding 2.1 m in length. Additionally, it weighs considerably less, with males rarely over 45 kg. Adult alligators are black or dark olive-brown with white undersides, while juveniles have bright yellow or whitish stripes which sharply contrast against their dark hides, providing them additional camouflage amongst reeds and wetland grasses. No average lifespan for an alligator has been measured. One of the oldest recorded alligator lives was that of Saturn, an American alligator who was hatched in 1936 in Mississippi and spent nearly a decade in Germany before spending the majority of its life at the Moscow Zoo, where it died at the age of 83 or 84 on 22 May 2020. Another one of the oldest lives on record is that of Muja, an American alligator who was brought as an adult specimen to the Belgrade Zoo in Serbia from Germany in 1937. Although no valid records exist about its date of birth, as of 2012, it was in its 80s and possibly the oldest alligator living in captivity. Alligators are native to only the United States and China. American alligators are found in the southeast United States: all of Florida and Louisiana; the southern parts of Georgia, Alabama, and Mississippi; coastal South and North Carolina; East Texas, the southeast corner of Oklahoma, and the southern tip of Arkansas. Louisiana has the largest alligator population. The majority of American alligators inhabit Florida and Louisiana, with over a million alligators in each state. Southern Florida is the only place where both alligators and crocodiles live side by side. American alligators live in freshwater environments, such as ponds, marshes, wetlands, rivers, lakes, and swamps, as well as in brackish water. When they construct alligator holes in the wetlands, they increase plant diversity and provide habitat for other animals during droughts. They are, therefore, considered an important species for maintaining ecological diversity in wetlands. Farther west, in Louisiana, heavy grazing by nutrias and muskrats is causing severe damage to coastal wetlands. Large alligators feed extensively on nutrias, and provide a vital ecological service by reducing nutria numbers. The Chinese alligator currently is found in only the Yangtze River valley and parts of adjacent provinces and is extremely endangered, with only a few dozen believed to be left in the wild. Far more Chinese alligators live in zoos around the world than can be found in the wild. Rockefeller Wildlife Refuge in southern Louisiana has several in captivity in an attempt to preserve the species. Miami MetroZoo in Florida also has a breeding pair of Chinese alligators.