Alligators Crocodiles Caimans and Gharials: Crocodylia

The order Crocodylia, also known as the crocodilians, includes 23 species of the most feared and most fascinating animals on the planet. They include 14 species of crocodiles and false gharials in the family Crocodylidae; eight species of alligators and caimans in the family Alligatoridae; and one species of gharial (GUR-ee-ul) in the family Gavialidae.

The crocodilians look somewhat like large lizards, but with thick and scaly skin, exceptionally strong tails, and large teeth-filled jaws. The scales on the upper surface, including the back and top of the tail, are large and rectangular in shape and have bony plates, called osteoderms (OSS-tee-oh-durms), just under the surface. Rows of these scales, which often have knobs or ridges, run from the rear of the head to the tail. On the legs and the sides of the body, the scales are smaller. Belly scales, which may also contain osteoderms, are large and smooth. Crocodilian tails are usually about as long as or a bit longer than the body, and in some species, like the Nile crocodile, the tails have a tall ridge of scales down the center.

The jaws contain large teeth, many of which show outside the mouth even when it is closed. People often describe the "grin" of a crocodilian. Of course, the animals are not actually smiling, but a slight upturn in the back of the jaw line of most species makes them look as if they are. Most, but not all, crocodilians have wide jaws. The Indian gharial is one species without a wide jaw. Instead, it has a very long and exceptionally thin pair of jaws filled with razor-sharp teeth. The false gharial, which looks much like an Indian gharial, has jaws that are only slightly wider and shorter than those of the Indian gharial.

The crocodilian body comes in shades of brown or gray, sometimes with a greenish or reddish tint. The upper surface is typically much darker than the belly, which is usually white to yellow. Bellies of dwarf caimans and dwarf crocodiles, however, are almost black. Many species have patterns of dark brown to black bands or blotches on the back and tail, and often these are most noticeable in youngsters.

The crocodilians are medium- to large-sized species. Cuvier's dwarf caiman is the smallest, with male adults reaching 5 feet (1.5 meters) long and females growing to 4 feet (1.2 meters) long. The largest species include the Indian gharial and the saltwater crocodile. Males of each species commonly grow to 16 feet (4.9 meters) and sometimes, although very rarely, reach 20 feet (6.1 meters). As with other crocodilians, the females are smaller overall than the males.