Elliptical Paphonotia Shell, Paphonotia elliptica

Elliptical Paphonotia Shell, Paphonotia elliptica. Shell collected from the beach in the greater Cabo San Lucas area, Baja California Sur, October 2018. Size: 2.2 cm (0.9 inches) x 1.8 cm (0.7 inches).

Phylogeny: The Elliptical Paphonotia, Paphonotia elliptica (G.B. Sowerby I, 1834), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Paphonotia is one of one hundred seven genera in this family, and there are only two species in this genus.

Description: Elliptical Paphonotia shells are thin, and vary in outline from elliptical to quadrate.  Both valves are equal in size and shape (equivalve). The shell’s exterior is sculpted with numerous coarse radial ribs, and raised concentric ridges (lamellae). The exterior of the shell varies in color from rose, to tan, to white, sometimes with brown maculations.  The interior is tan to white, with brown blotches at both ends. The Elliptical Paphonotia Shells reach a maximum of 4.0 cm (1.6 inches) in length and 3.4 cm (1.3 inches) in height.

Habitat and Distribution: Elliptical Paphonotias are found settled into holes in rocks in the intertidal zone and to depths up to 30 m (100 feet). They are a tropical Eastern Pacific species. In Mexican waters they range from Mazatlán, Sinaloa, to Guatemala. They have not been documented from the Baja Peninsula, though the pictured specimen was collected dead in the greater Cabo San Lucas area of Baja California Sur.

Ecology and Behavior:  Elliptical Paphonotias 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. There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Petricola elliptica, Petricola oblonga, Petricola solida, Petricola solidula, Venerupis fimbriata, Venerupis foliacea, and Venerupis paupercula.