Galapagos Cowry Helmet Shell, Cypraecassis tenuis

Galapagos Cowry Helmet Shell, Cypraecassis tenuis. Shell courtesy of the commercial fishermen of the greater Los Cabos area, Baja California Sur, January 2011. Size: 15.2 cm (6.0 inches) x 9.2 cm (3.6 inches).

Phylogeny: The Galapagos Cowry Helmet, Cypraecassis tenuis (W. Wood, 1828), is a gastropod mollusk that is a member of the Cassidae Family of Helmet Shells. The genus Cypraecassis is one of thirteen genera in this family, and there are six species in this genus. They are also known as the Thin-shell Helmet and in Mexico as Caracol Casco Delgado.

Description: The Galapagos Cowry Helmet Sshell is thinner and lighter than most Helmet Shells. They are somewhat egg-shaped, with a low spire. The aperture is narrow but widens as it approaches the anterior end. The shoulder is knobbed, with the knobs often extending down the body. Exterior sculpting includes both wide bands spiraling down the body whorl and small ridges running the length of the body. The shell’s exterior is mottled light and dark brown in color, with varying amounts of white cross-hatching. The aperture can be tan to bright burnt orange. The outer lip of the aperture is often banded with brown and cream or white.  Galapagos Cowry Helmet Shells reach a maximum of 18.0 cm (7.0 inches) in length and 10.2 cm (4.0 inches) in height.

Habitat and Distribution: Galapagos Cowry Helmets are found on sand near rocks, and under rocky ledges. They live subtidally, at depths between 3 m (10 feet) and 46 m (150 feet). They are a subtropical to tropical Eastern Pacific species. In Mexican waters they range from San Juanico, Baja California Sur to Guatemala.  They are found in the Gulf of California from Bahía de los Ángeles, Baja California,  to Cabo San Lucas, Baja California Sur.

Ecology and Behavior: Galapagos Cowry Helmets are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in Family Cassidae are predators that feed primarily on echinoderms, such as sea urchins and sea stars. 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. Galapagos Cowry Helmets are rare, and highly sought by shell collectors. From a conservation perspective they have not been formally evaluated.

Synonyms:  Cassis massenae, Cassis tenuis, and Cypraecassis (Cypraecassis) tenuis.