The alligator snapping turtle is characterized by a large, heavy head, and a long, thick shell with three dorsal ridges of large scales (osteoderms), giving it a primitive appearance reminiscent of some of the plated dinosaurs.
The inside of the turtle's mouth is camouflaged, and it possesses a vermiform (i.e., "worm-shaped") appendage on the tip of its tongue used to lure fish, a form of Peckhamian mimicry.