Spirate Turban Shell, Pomaulax spiratus

Spirate Turban Shell, Pomaulax spiratus. Shell collected off the beach of the greater Cabo San Lucas area of Baja California Sur, October 2019. Size: 3.2 cm (1.3 inches) x 3.4 cm (1.3 inches).Collection, photography and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Spirate Turban, Pomaulax spiratus (Dall, 1911), is a gastropod mollusk that is a member of the Turbinidae Family of Turban Shells. The genus Pomaulax is one of eighteen genera in this family, and there are seven species in this genus. They are known in Mexico as Turbante Espiral.

Description: Spirate Turban Shells have a steep-sided cone-shape, which consists of four or five whorls. They are slightly taller than they are wide. Their sides are sculpted with strong radiating ribs and spiral ridges, and their base with a spiral cord. The exterior of the shell is pinkish or reddish brown and the aperture is pearly white. The Spirate Turban Shells reach a maximum of 3.7 cm (1.5 inches) in height and 3.0 cm (1.2 inches) in diameter.

Habitat and Distribution: Spirate Turbans are an uncommon subtropical to tropical Eastern Pacific species. There is limited information on their distribution. They are found on rocks, subtidally to depths of up to 10 m (33 feet).  They are a subtropical Eastern Pacific species that have a poorly documented range. They are known from Sinaloa and Baja California Sur and discontinuously range south to Costa Rica. Most shells are found as dead specimens in shallow water or washed up on the beach.

Ecology and Behavior: Spirate Turbans are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in the Pomaulax Genus are grazers and depositional feeders that feed primarily on algae and detritus. They are gonochoric and reproduce sexually through broadcast spawning with external fertilization.  Their engagement in any type of commensal, parasitic, or symbiotic relationships has not been formally documented. From a conservation perspective they have not been formally evaluated.

Synonyms:  Astraea spirata, Pachypoma inaequale spiratum, and Pachypoma inaequale var. spiratum.