Large-ribbed Cardita Shell, Cardites crassicostatus

Large-ribbed Cardita, Cardites crassicostatus. Shell collected off the beach of Punta Chivato, Baja California Sur, June 2025. Size: 4.5 cm (1.8 inches) x 4.2 cm (1.7 inches) x 1.7 cm (0.7 inch). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Large-ribbed Cardita, Cardites crassicostatus. Shell collected off the beach of Punta Chivato, Baja California Sur, June 2025. Size: 6.4 cm (2.5 inches) x 6.0 cm (2.4 inches) x 2.6 cm (1.0 inch). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Large-ribbed Cardita, Cardites crassicostatus. Shell collected by the deepwater shrimp trawlers off the southwest coast of Baja California Sur, April 2010. Size: 6.5 cm (2.6 inches) x 6.5 cm (2.6  inches).

Phylogeny: The Large-ribbed Cardita, Cardites crassicostatus (G.B. Sowerby I, 1825), is a bivalve mollusk that is a member of the Carditidae Family of Little Heart Shells. The genus Cardites is one of thirty-seven genera in this family, and there are thirteen species in this genus. They are also known as the Thick-ribbed Cardita Shell.

Description: The Large-ribbed Cardita Shell has a a rounded rectangular profile and is plump and equivalve (both valves equal in size and shape). The exterior displays fifteen to twenty wide radial ribs, which terminate in a squared-off scalloping at the margin. The exterior of the shell is orange with white and brown blotches; the interior is white. The periostracum is thin, tan to dark brown, and often eroded. Large-ribbed Cardita Shells reach a maximum of 6.8 cm (2.7 inches) in length and 6.8 cm (2.7 inches) in height.

Habitat and Distribution: Large-ribbed Carditas are found in rubble from the intertidal zone to depths up to 55 m (180 feet). They 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 north of Todos Santos, Baja California Sur, along the central and northwest coasts of the Baja Peninsula.

Ecology and Behavior:  Large-ribbed Carditas are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective they have not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.

Synonyms: Cardita (Glans) sulcosa, Cardita cuvieri, Cardita michilini, Cardita sulcosa, Cardium locinoides, and Venericardia crassicostata.