You can tell the difference by looking at their jawlines.
Crocodylia is the taxonomic name for all alligators, crocodiles and other reptiles. According to Pathology of Wildlife and Zoo Animals, Crocodylia can be divided into three main families: Alligatoridae or alligators, Crocodylidea or crocodile and Gavialidae.
According to the New York Times, these Crocodylia share an evolutionary ancestor. However, about 80 million years ago, during the Late Cretaceous, Alligatoridae, and Crocodylidae, diverged and began their own evolutionary journey. Both Crocodiles as well as alligators have remained fairly similar over millions of years of evolution, but there are surprising differences that are easy for people to notice.
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What is the difference between crocodiles and alligators?
Crocodiles are very similar to alligators at first glance. However, closer inspection reveals that they have very different noses. One quick way to tell a crocodile and an alligator is to look at their jawline. The overbite of alligators means that the teeth at the bottom of the jaw fit into the sockets along the top jawline. According to Biology and Evolution of Crocodylians, the teeth in the bottom row of acrocodiles' jaws sit outside of the mouth and fit into grooves at the top of the jaw. Their heads are also an important identifier. Crocodiles, on the other hand, have a rounded U-shaped, wide-spaced, and rounded nose that is both short and long. Some exceptions to this rule include the mugger-crocodile (Crocodylus paleustris), which, according to San Diego Zoo Wildlife Alliance, has a round snout that is reminiscent of an alligator.
These reptiles both have tiny, black specks on their heads called integumentary sensory organs (ISOs). These sensory organs enable predators to detect changes in water pressure caused by potential prey. The ISOs are located only on the head and around alligators' mouths. Crocodiles, however, have ISOs on nearly every scale of their bodies according to the Journal of Experimental Biology.
The mouth of an American alligator (Alligator Mississippiensis) contains integumentary senses. Getty Images image credit
The differences between the reptiles go beyond skin depth. Researchers found that alligators' forelimbs had a shorter humerus bone than crocodiles and their hindlimbs had shorter femurs in a 2018 study in Royal Society Open Science.
Where are alligators and crocodiles found?
The place they live is a major difference between alligators, crocodiles, and other animals. According to a study published by the Journal of Comparative Physiology, crocodiles possess lingual salt glands - located on their tongues – which allow them expel excess salt from themselves. This ability allows them live in salty marine environments such as Australia's saltwater Crocodiles (Crocodylus Porosus), which are found throughout mangroves swamps and deltas. The salt gland in alligators is the same, but it is less effective than the rest and limits their tolerance to salt water. Alligators prefer freshwater habitats like lakes and marshes.
These differences in salt tolerance could also be responsible for the differences in their global distribution. According to National Geographic, Crocodile species can also be found throughout the Americas, Africa and Asia, while alligators tend to be found in North America and South America.
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