Common snapping turtle

The carapace varies in color from black to light brown. Young snapping turtles have three prominent, saw-toothed keels along the top of the carapace, but these become less obvious as the turtle ages. The adult head is large and the plastron is small with nine scutes. The skin is gray to black or yellow. There are barbels at the tip of the chin. The tail is long with a saw-toothed upper edge. The neck and tail are each as long as the carapace. This turtle is often covered with algae, and adult males are usually larger than adult females.

(info from "A Field Guide to Oklahoma's Amphibians and Reptiles")