Angle-mouth Nutmeg Shell, Trigoniostoma gonostoma

Angle-mouth Nutmeg Shell, Trigoniostoma gonostoma. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2022. Size: 3.1 cm (1.2 inches) x 2.4 cm (0.9 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Angle-mouth Nutmeg Shell, Trigonostoma goniostoma. Shell collected off the beach in the greater Los Cabos area, Baja California Sur, May 2008. Size: 3.2 cm (1.6 inches) x 2.6 cm 1.0 inch), November 2018. Collection, identification and photo courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Angle-mouth Nutmeg, Trigonostoma goniostoma (G. B. Sowerby I, 1832), is a gastropod mollusk that is a member of the Cancellariidae Family of Nutmegs. The genus Trigonostoma is one of  thirty-eight genera in this family, and there are twenty-two species in this genus. This species is also known as the Rigid Nutmeg.

Description: The Angle-mouth Nutmeg shell is angular in overall appearance, with four or five straight-sided, very wide whorls, giving the spire a teared look, like a wedding cake. The shell has strong spiral and lengthwise ribs that form knobs, where they cross each other, on the sides and broad, deep shoulders of the whorls. The body whorl is large and the aperture is triangular. When viewed from the bottom, a deep pit (umbilicus) that runs through the center of the shell, to the spire is evident. They have 7 or 8 varices per whorl. Their columellar plicae (teeth) are present but not prominent. The exterior of the shell is cream to light tan in color, with darker brown lines and blotches on the shoulder areas; the interior is white. Angle-mouth Nutmeg Shells reach a maximum of 3.5 cm (1.4 inches) in length and 2.4 cm (0.9 inches) in height.

Habitat and Distribution: Angle-mouth Nutmegs are found within sand substrate in the intertidal zone, and to depths up to 15 m (50 feet). They are a tropical Eastern Pacific species. In Mexican waters they range from Magdalena Bay, Baja California Sur to Guatemala. They are found throughout the Gulf of California.

Ecology and Behavior: Species in this family are suctorial feeders, sucking soft tissue, blood, and other fluids out of fish and egg capsules. Angle-mouth Nutmegs are gonochoric and reproduce sexually.  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.

Synonym: Cancellaria goniostoma.