Angle-mouth Screw Shell, Caviturritella gonostoma

Angle-mouth Screw Shell, Caviturritella gonostoma. Shell collected off the beach in the greater Punta Chivato area, Baja California Sur, December 2022.  Size: 12.7 cm (4.9 inches) x 2.8 cm (1.8 inches). Photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Angle-mouth Screw Shell, Caviturritella gonostoma (Vallenciennes, 1832), is a gastropod mollusk that is a member of the Turretellidae Family of Turrets or Tower Shells. The genus Caviturritella is one of twenty-four genera in this family, and there are four species in this genus.

Description: Angle-mouth Screw Shell shells are solidly built shells with many flat-sided whorls wand a small aperture. The exterior is sculpted with fine spiral lines with younger specimens having a spiral ridge in the middle of the whorl that disappears with maturity. The exterior of the shell is gray to purplish brown in color, with white mottling. The Angle-mouth Screw Shell is one of the larger Turrets in the area reaching a maximum of 16.3 cm (6.4 inches) in length and 3.5 cm (1.4 inches) in height.

Habitat and Distribution: Angle-Mouth Screw Shells are found on and within mud and sand substrate from the intertidal zone to depths up to 6 m (20 feet). They are a tropical Eastern Pacific species. In Mexican waters they range from Bahia San Juanico, Baja California Sur to Guatemala. They are found throughout the Gulf of California.

Ecology and Behavior: Species in this family are suspension feeders, using mucous strings to capture plankton and suspended organic matter. They are preyed upon by crabs and other gastropods, especially Moon Snails and Murexes. They are known to host parasitic trematodes. Angle-Mouth Screw Shells are gonochoric. Reproduction is sexual, with internal fertilization.  Their eggs  laid in a cluster of spherical, stalked capsules.

Synonyms: Turritella goniostoma, Turritella gonostoma, and Turritella punctata.