Spiny softshell turtles have soft, flat, rounded carapaces without scutes. The edges are pliable with small spines, in the eastern subspecies the spines are toward the front of the carapace. Some subspecies have the spines on the posterior part of the carapace (A. s. pallida) while some have them on most parts of the carapace (Behler and King 1998). The nose is long, tapered, and upturned at the end with ridges (Harding 1997). Unlike gulf spiny soft-shell turtles (A. s. aspera), with two distinct black-bordered yellow stripes on each side of the head that come together before the long neck, eastern spiny soft-shell turtles (A. spinifera spinifera) have two black-bordered yellow stripes that travel along the neck and do not connect (Conant and Collins 1998). The plastron is whitish or yellow with bones visible underneath. They have claws and their feet are webbed for swimming. The body is olive or tan with black speckles and a dark rim around the edge of their carapace. In A. s. aspera two or more dark lines can be found bordering the rear margin of the shell and in A. s. pallida, the black ring is lacking. Some subspecies have whitish spots on their whole carapace, the posterior half of their carapace, or on the rear third of their carapace, these subspecies being A. s. guadalupe, A. s. pallida, and A. s. emoryi respectively. These characteristics intergrade where hybrid zones occur. There is some sexual dimorphism. Adult males retain the juvenile's olive and yellow coloration with black "eyespots", have a slightly rougher carapace than females, and are smaller than females, with a carapace length of 12.7 to 24 cm. Males also have longer and thicker tails that females. The carapace of females darkens during adulthood and becomes a mottled gray. The length ranges from 24 to 48 cm and the tail barely extends past the edge of her carapace.
Range length: 12.7 to 48 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes shaped differently