Pyramid pigtoe

Pleurobema rubrum (Rafinesque, 1820)

Pyramid pigtoe
Pleurobema rubrum, INHS 3122. Little Wabash River, Wayne County, Illinois. Length: 2.4 inches (6.1 cm).

Other common names: Pink pigtoe.

Key characters: Triangular and elongate shell, shallow sulcus present, rose-colored nacre, moderately deep beak cavity.

Similar species: All other pigtoes (Fusconaia and Pleurobema).

Description: Shell thick, triangular and elongate, and moderately inflated. Anterior end rounded, posterior end rounded to bluntly pointed. Dorsal and ventral margins curved. Umbos high, projected forward, and anterior to rest of shell. Shell smooth or satin-like. Shallow sulcus present. Periostracum brown or chestnut, with faint green rays on the umbos. Length to 4 inches (10.2 cm).

Pyramid pigtoe distribution 1992

Pseudocardinal teeth well developed; two in the left valve, one in the right. Lateral teeth straight or slightly curved. Beak cavity moderately deep. Nacre pink or rose-colored in most individuals, occasionally white.

Habitat: Medium to large rivers in sand or gravel in areas with a good current.

Status: Widespread but rare in the Ohio River drainage. Federal Candidate (Category 2). Endangered in Indiana and Ohio. Species of Special Concern in Illinois.

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