Frilled Venus Clam Shell, Chione undatella

Frilled Venus Clam Shell, Chione undatella. Shell collected off the beach of Punta Chivato, Baja California Sur, December 2025. Size: 2.8 cm (1.1 inches) x 2.3 cm (0.9 inches) x 0.8 cm (0.3 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Frilled Venus Clam Shell, Chione undatella. Shell collected off the beach of Punta Chivato, Baja California Sur, December 2025. Size: 3.5 cm (1.4 inches) x 3.5 cm (1.4 inches) x 1.1 cm (0.4 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Frilled Venus Clam Shell, Chione undatella. Shell collected off the beach of Punta Chivato, Baja California Sur, December 2025. Size: 3.7 cm (1.5 inches) x 3.5 cm (1.4 inches) x 1.1 cm (0.4 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Phylogeny: The Frilled Venus Clam, Chione undatella (G.B. Sowerby I, 1835), is a bivalve mollusk that is a member of the Veneridae Family of Venus Clam Shells. The genus Chione is one of one hundred seven genera in this family, and there are eleven species in this genus. They are also known as the Wavy Chione Shell and in Mexico as Almeja de Costillas Ondeadas, Almeja Ronosa del Mar de Cortez, and Venus Reñosa.

Description: The Frilled Venus Clam Shell is thick and moderately inflated,  with an oval or trigonal outline. The exterior is sculpted with closely spaced concentric ridges, and low, broad, radial ridges. They have a short siphon and a well-developed foot. The exterior of the shell is whitish with brown blotches, chevrons, or broken, radiating, bands, The interior is white with purple near the posterior end. The Frilled Venus Shells reach 6.6 cm (2.6 inches) in length and 5.9 cm (2.3 inches) in height.

Habitat and Distribution: Frilled Venus Clams reside in shallow burrows within firm sand and sandy mud bottoms. They live intertidally, and to depths up to 90 m (300 feet). They are found in bays and other places where they are protected from wave action and strong currents. They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean including the Revillagigedo Islands.

Ecology and Behavior:  Frilled Venus Clams are infaunal suspension feeders that feed primarily on planktonic algae and suspended organic matter. Their predators include fish, crabs, sea stars, and shorebirds. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. The Onyx Slipper Shell, Crepidula onyx, is a known epibiont on this species.  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. Frilled Venus Clams are edible, and are subject to artisanal, commercial, and recreational harvesting.

Synonyms: Chione simillima, Chione undatella taberi, Venus entobapta, Venus (Chione) excavata, Venus neglecta, Venus perdix, Venus simillima, and Venus undatella.