Tritogonia verrucosa (Rafinesque, 1820)
Other common names: Buckhorn, peanut, turkey wing.
Key characters: Elongate, posterior wing with folds, sides of the shell covered with pustules.
Similar species: Rabbitsfoot.
Description: Shell thick, elongate, and compressed. Anterior end rounded, posterior end squared or truncated in males, elongate and rounded in females. Dorsal margin straight to slightly curved, ventral margin usually arched. Umbos low, only slightly elevated above the hinge line. Beak sculpture of a series of pronounced ridges continuing down the sides. Entire shell (except the rounded posterior ridge of the female) covered with irregularly sized and arranged pustules. Periostracum green or light brown, becoming dark brown to black in older shells. Length to 8 inches (20.3 cm).
Pseudocardinal teeth large, serrated, and well developed; two in the left valve, one in the right (occasionally with a small tooth on either side). Lateral teeth long, straight, and striated; two in the left valve, one in right. Beak cavity deep. Nacre white, iridescent posteriorly.
Habitat: Medium to large rivers in mud, sand, or gravel.
Status: Widespread but relatively uncommon. Endangered in Iowa. Threatened in Wisconsin.