Petricola Clam Shell, Petricola insignis

Petricola Clam Shell, Ptricola insignis. Shell collected off the beach of Punta Chivato, Baja California Sur, April 2025. Size: 3.2 cm (1.3 inches) x 2.7 cm (1.1 inches) x 1.1 cm (0.4 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Petricola Clam Shell, Ptricola insignis. Shell collected off the beach of Punta Chivato, Baja California Sur, April 2025. Size: 3.4 cm (1.4 inches) x 2.7 cm (1.1 inches) x 0.9 cm (0.4 inches). Collection and photographs courtesy of Colin Campbell, DVM, Punta Chivato. Identification courtesy of by Dr. Paul Valentich-Scott, Santa Barbara, California.

Phylogeny: The Petricola Clam Shell, Petricola insignis (Deshayes, 1854), is a bivalve mollusk that is member of the Veneridae Family of Venus Clams. They are in the subfamily Petricolinae. The Petricola Genus is one of eight genera in this subfamily, and there are twenty-seven species in the Petricola Genus.  The genus name  Petricola comes from the Latin words meaning “rock dweller”. This refers to these shells boring into rock to make a place to live. The species name insignis means “distinguished”, “remarkable”, or “outstanding”.  These shells are also called Rock Boring Clams. Until recently this genus was part of the Petricolidae Family, which has been declared not to be valid as it is superseded by the Veneridae Family.

Description: Petricola Clam Shells are irregularly ovate to quadrate in outline and moderately inflated in profile. These shells are strong and robust. They are as high, or higher, than they are long. The anterior end is short and rounded. The posterior tends to be truncate (appearing chopped off) and rounded ventrally. The beaks are prominent and the interior hinge is strong. Petricola Clam Shells are sculpted with commarginal lamellae and numerous, fine, radial ribs. The pallial sinus is broad and fairly deep. The exterior of these shells is whitish to brownish in color. The interior may be pinkish-orange or orangish-brown. The hinge and interior margins are darker reddish-brown. Petricola Clam Shells reach a maximum of 4.4 cm (1.7 inches) in length.

Habitat and Distribution: Petricola Clam Shells burrow into coral and other calcareous substrates. They live in the intertidal zone, and to depths of 32 m ( 105 feet). Petricola Clam Shells are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from along the entire west coast of the Baja Peninsula.

Natural History: Petricola Clam Shells are a poorly researched and documented species. They are infaunal suspension feeders, which feed on plankton and suspended organic matter. Their predators are not well documented, They are thought to be prey for fish, crabs, shorebirds and gastropods. Petricola Clam Shells are gonochoric and reproduce sexually, through broadcast spawning. Their engagement in any type of commensal, parasitic, or mutualistic relationship has not been formally documented.

Conservation: From a conservation perspective the Petricola Clam Shell has not been formally evaluated.

Synonyms: Petricola (Naranio) charapota, Petricola (Petricola) insignis, Petricola charapota, Petricola lucasana, and Venerupis insignis.