The world of alligators holds a rich biodiversity. Today, the American and Chinese alligators represent the last-standing symbols of this vast legacy. Yet, the types of alligators that once roamed the earth were as varied as the landscapes they inhabited. Echoes of their diversity now serve as a cautionary tale.
The conservation status of these ancient reptiles begs our attention. So, join us as we gain a deeper understanding of these creatures.
Taxonomic Classification of Alligators
Alligators, the imposing reptiles from the genus Alligator, are part of the Alligatoridae family under the crocodilian order Crocodilia. Sharing familial ties with caimans in the Alligatorinae subfamily, these creatures are distinct from their distant relatives – the true crocodiles in the family Crocodylidae, and Gavialidae's gharial and false gharial.
Regarding evolution, the first alligators surfaced nearly 37 million years ago during the Oligocene epoch1. Today, there are only two extant species native to the United States and China.
Meanwhile, crocodile species are more widespread. There is the Cuban crocodile in the Americas and the Saltwater crocodile in Asia and Australia. A Spectacled caiman is less common, only inhabiting regions in Central and South America.
Alligators only live in freshwater environments, a stark contrast to the saltwater crocodiles, who inhabit freshwater and saltwater equally. This divergence extends beyond habitats to their physical features, too.
An alligator's broad and U-shaped snout differs from the crocodile's pointed, aggressive V-shaped fin. Moreover, the less aggressive alligator's biting strength approximates roughly 2,900 psi, compared to the 3,000 psi of a Nile crocodile and the 3,700 psi of a Saltwater crocodile.
Distinguishing a young alligator from a caiman could also be a task for the untrained eye. A close observation would reveal the alligator's smoother belly and back scales, rounder teeth, and larger size compared to the caiman. Furthermore, caimans also have more scales on their heads.
In this article, aside from mentioning more differences between these crocodilians, we focus on the distinguishing features of each alligator, living and extinct.
Related Read: Alligator Facts.
9 Types of Alligator Species
1. American Alligator (Alligator mississippiensis)
American alligators, often referred to simply as gators, are residents of the wild Southeastern United States stretching from the Lowcountry in South Carolina to Florida's Everglades and west to the southeastern pockets of Texas.
Sporting colors from olive to gray and black, their predominantly dark dorsal scales provide a stark contrast against the lighter tones of the American crocodile. Moreover, they have cream-colored undersides.
These gators have an average length of 11 ft 2 in, and mature males tip the scales at around 790 lb. Their dietary preference spans from fish and amphibians to reptiles and birds, and even mammals, asserting their status as apex predators.
The American alligator makes its home in wetland ecosystems, be it swamps, rivers, ponds, or lakes. They can also be found in seasonal wetlands like Carolina Bays, a common habitat for females and juveniles. These reptiles are also known as keystone species. They construct alligator holes, which become vital wet and dry habitats for other organisms.
Despite sharing territory with American crocodiles in South Florida, American alligators show less tolerance for saltwater but greater resilience towards cooler temperatures. The nonfunctioning salt glands on their tongues explain their preference for freshwater bodies.
2. Chinese Alligator (Alligator sinensis)
The Chinese Alligators are endangered crocodilians living in the waterways of China's Yangtze River basin. It is one of the two remaining alligator species in the world, with an average size of 5 to 7 feet.
This type of alligator digs complex burrows near bodies of water. These serve as shelter during winter and a shaded spot during summer.
Female Chinese Alligators are fiercely maternal and protect their nests to ensure the safety of their young. They guide their hatchlings to the water, allowing them to take their first steps into the outside world.
These alligators feed on small fish and invertebrates, using their broad snout and powerful jaws to capture prey.
Sadly, the Chinese Alligator is critically endangered2. Rapid habitat loss, also escalated by poaching and pollution, dwindled their count to a low number of 68 to 86 mature individuals in the wild.
The severe fragmentation of the population continues unabated, even as alligator hunting recedes. Their survival depends on urgent habitat restoration and robust measures to tackle the adverse impacts of environmental contamination and reduced genetic diversity.
Because of their status and conservation efforts, far more Chinese alligators live in zoos worldwide than in the wild.
3. Haile Alligator (Alligator hailensis)
The Haile Alligator existed millions of years ago during the Miocene epoch. These alligators were named after their birthplace, the Haile limestone quarries in Florida. Interestingly, they were significantly larger than modern American alligators, with a length of up to 16 feet.
The elongated structure of their skulls suggests that their hunting and dietary habits may have differed from present-day alligators. These apex predators likely fed on fish, turtles, and occasionally small mammals.
Moreover, they lived in freshwater habitats like marshes, rivers, and swamps, similar to modern alligators' habitats.
4. Alligator mcgrewi
During the Miocene epoch, around 23 and 5.3 million years ago, the now-extinct Alligator mcgrewi was a common sight in modern-day Nebraska. Fossils reveal that these medium-sized alligators were semi-aquatic, similar to their present-day relatives.
Plant fossils discovered alongside Alligator mcgrewi suggest that they lived in a warm, humid environment with lush vegetation.
They were likely predators of fish, small mammals, and other reptiles. Alligator mcgrewi probably laid eggs in carefully constructed nests, as their descendants do today.
The cause of their extinction remains uncertain, but climatic changes during the late Miocene may have played a role.
5. Alligator mefferdi
During the Miocene epoch, the region of Nebraska and Colorado was home to various animals, including a unique species of alligator called the Alligator mefferdi, which is now extinct.
This alligator had a broad, flat skull with robust, blunt teeth, making it easier to crack open hard-shelled prey. Its solitary habits suggest it spent its life grappling with tough, shelled animals in freshwater habitats.
Although it is now extinct, its legacy lives on through fossils that glimpse an ancient world. H.T. Martin discovered this species, though its name came from his fellow paleontologist, Samuel Wendell Williston Mefferd.
6. Alligator munensis
The Alligator munensis was an extinct species that lived during the Miocene epoch. Paleontologists discovered its fossilized remains in Nebraska and South Dakota, suggesting that it lived in freshwater habitats such as swamps, rivers, and marshes.
Experts estimate it was about the same size as the modern American alligator, reaching up to 15 feet.
It is believed to be a semi-aquatic creature with powerful jaws that could snap like a steel trap, and it likely fed on fish, birds, and small mammals. They would bask in the sun to keep warm and create 'gator holes' in wetlands for hunting and nesting.
7. Olsen's Alligator (Alligator olseni)
The Olsen's Alligator existed during the Oligocene epoch from around 23 to 33.9 million years ago. This ancient alligator species used to reside mainly in Florida.
One of the distinguishing features of the Olsen's Alligator is its smaller size, with adult specimens measuring between 2 and 3 meters in length.
Olsen's alligator had a broad, flat skull and blunt snout, suggesting that its diet comprised hard-shelled creatures such as mollusks and crustaceans.
Moreover, this animal used its robust, cone-shaped teeth and powerful jaws to break open hard shells or exoskeletons. This prehistoric alligator inhabited freshwater habitats like rivers and lakes.
8. Alligator prenasalis
During the Oligocene epoch, around 33.9 to 23 million years ago, a unique alligator species known as Alligator prenasalis existed.
This creature had an elongated snout, which made it efficient at catching swift-swimming prey. The Alligator prenasalis could grow up to 13 feet long.
It was primarily found in freshwater bodies in the Great Plains region of North America, where it built nests using vegetation and fiercely protected its offspring.
The reason for the extinction of the Alligator prenasalis remains unknown, but it is believed that it might have been due to climate change or competition with other predators.
9. Alligator thomsoni
During the Miocene epoch, the Alligator thomsoni once lived in the freshwater habitats of what is now known as the state of Nebraska. It lived around 23 to 5.3 million years ago.
The fossil fragments suggest a creature that was possibly up to 13 feet long, with strong jaws full of teeth. Moreover, its teeth and jaws were strong enough to crush hard-shelled prey such as turtles.
Brochu, C. A. (1999). Phylogenetics, taxonomy, and historical biogeography of alligatoroidea. Memoir /, 6, 9.
Jiang, H. & Wu, X. (2018). Alligator sinensis. The IUCN Red List of Threatened Species 2018: e.T867A3146005.