Pleurobema clava (Lamarck, 1819)
Other common names: Northern clubshell.
Key characters: A triangular shell with an elongated posterior end and green rays on umbo.
Similar species: Pyramid pigtoe, ellipse
Description: Shell triangular, elongate, relatively thick, and compressed to moderately inflated. Anterior end rounded, posterior end bluntly pointed. Dorsal margin curved and slanted down toward the point of the shell, ventral margin straight to slightly curved. Umbos low, projected far forward and only slightly elevated above the hinge line. Beak sculpture when visible of a few sharp ridges at the tip of the umbo. Shell smooth, with an occasional crease or groove present on posterior lateral surface in some individuals. Periostracum yellowish brown with prominent broken green rays present in the umbo region on most specimens; older shells dark brown or black. Length to 3 inches (7.6 cm).
Pseudocardinal teeth small and well developed; two in the left valve, one in the right. Lateral teeth moderately long, straight to slightly curved; two in the left valve, one in the right (occasionally with an additional shorter lateral tooth in the right valve). Beak cavity moderately deep. Nacre pearly white, iridescent posteriorly.
Habitat: Medium to large rivers in gravel or mixed gravel and sand.
Status: Proposed for Federal Endangered status. Endangered in Illinois, Indiana, Michigan, and Ohio.