How to tell the modern crocodilians apart

Crocodiles, alligators [including the closely related caimans], and gharials make up the group of animals known as the modern-day crocodilians.

All crocodilians have at least 60 teeth. Like sharks, they are able to replace lost or worn-out teeth by growing new ones.

Crocodile
Almost all of its teeth "stay" on the outside of its mouth when closed.

Ancient crocodiles lived in southern California during the Eocene, based on fossil remains found in the middle Eocene Santiago Formation in San Diego County. The two teeth shown above are 16 and 17 mm in length (left to right).

Alligator
All of the its lower teeth fit inside the upper ones. When it closes its mouth, only the top teeth can be seen. Its head is broader, flatter, and less triangular than that of a crocodile.

Alligators can live in slightly cooler climates than crocodiles and gharials. Caimans, which belong to the same family as alligators, are native to the Americas, primarily South America.    


Gharial (pronounced GAIR-ee-ul)
It has a very long and very narrow mouth, with over a hundred teeth–more than any other modern-day crocodilian. Unlike the teeth of crocodiles and alligators, a gharial's teeth are all about the same size. Garhials live in India.

Side view of the false gharial Tomistoma schlegelii, 19.75 in. long.
False gharial are freshwater crocodiles found uncommonly today in Malaysia, Boreno, Sumatra, and Java. The snout of T. schlegelii is shorter and more similar to true crocodiles than to the true gharial, but T. schlegelli might be a intermediate form.

Top view of the previous specimen. It is interesting to note that the "holes" in the posterior region of this skull are reminiscent of the supratemporal fenestra ["holes"] found in some dinosaurs (e.g., see my April 23, 2025 post on the skull of the early dinosaur Herrasaurus).