The Order Crocodylia (also sometimes spelled Crocodilia) is composed of three families, eight genera, and 22 species. These large semi-aquatic reptiles inhabit fresh, brackish, and salt water environments of tropical, subtropical, and warm temperate regions of the world. Adults range from 1.5-7 m (5-23 ft) in total length. The crocodilians are a very successful group, and their body form has not changed for 75 million years. They have a long snout, four well-developed legs, and a long, muscular tail used to propel them through the water. Based on their internal anatomy, they are the most evolutionarily advanced of all the reptiles.
American Alligator (Alligator mississippiensis)