Trigonal Horse Hoof Shell, Pilosabia trigona

Trigonal Horse Hoof Shell, Pilosabia trigona. Shell collected off the beach of Punta Chivato, Baja California Sur, March 2025. Size:  1.7 cm (0.7 inches) x 1.4 cm (0.6 inches) x 0.7 cm (0.3 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Trigonal Horse Hoof Shell, Pilosabia trigona. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, May 2000. Size: 1.6 cm (0.6 inches) x 1.0 cm (0.4 inches).

Trigonal Horse Hoof Shell, Pilosabia trigona. Shell collected off the beach of Punta Chivato, Baja California Sur, March 2025. Size:  1.8 cm (0.7 inches) x 1.6 cm (0.6 inches) x 0.9 cm (0.4 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

The Trigonal Horse Hoof, Pilosabia trigona (Gmelin, 1791), is a gastropod mollusk that is a member of the Hipponicidae Family of Hoof Shells. They are also known as the Bearded Horse Hoof Shell, the Triangular Bearded Hoof-Limpet Shell and the Trigonal Hoof Shell and in Mexico as Caracol Pezuña. The shell has a circular to tear-drop shaped profile with an apex that is moderately to highly elevated that is often worn smooth. The exterior of the shell is sculpted with strong, fine ribs. The yellowish-brown periostracum forms bristles along these ribs that may extend over the edge of the shell, like a beard. The exterior of the shell is white to cream colored; the interior is white with yellow, brown, or bluish blotches. The Trigonal Horse Hoof Shells reach a maximum of 2.2 cm (0.9 inches) in length and 1.4 cm (0.5 inches) in height.

Trigonal Horse Hoofs are found on, and under rocks within the intertidal zone to depths up to 6 m (20 feet). They are found in the Sea of Cortez, from Bahía Concepción to the Cabo San Lucas, Baja California Sur, and range south to Ecuador. They have not been documented from the Pacific Coast of the Baja Peninsula. They are also found in the Central and Western Pacific, and the Indian Ocean.

Synonyms:  Amalthea barbata, Hipponix barbatus, Hipponix pilosus, Patella trigona, Pileopsis pilosus, and Pilosabia pilosa.