Three-toed Box Turtle
Terrapene carolina

Size:  6-8 in (along carapace)
Distribution:

Eastern 3/4 of the state.  There are two species of box turtles in Oklahoma, the ornate box turtle, Terrapene ornata, and the three-toed box turtle. The three-toed box turtle can be distinguished from the ornate in that it has a higher, more rounded dome and the belly tends to be plain. It gets its name as most have only three toes on the hind feet. To make it even more complicated, some three-toeds can have four toes on their hind feet. The subspecies found in Oklahoma is T. c. triunguis, meaning "three-toed," whereas the eastern box turtle, T. c. carolina, is not found in Oklahoma.

Box turtles are omnivorous, preferring to feed on fruits and vegetation during the day. Like their close relatives the tortoises, they are excellent burrowers, highly territorial, and have relatively long lifespans. Although they do well in captivity, it is discouraged to remove them from the wild due to their territoriality and longevity. 

Variations in three-toed box turtle carapace patterns.
Plastron of a three-toed box turtle. Notice the relatively plain plastron.