Thorn Latirus Shell, Opeatostoma pseudodon

Thorn Latirus Shell, Opeatostoma pseudodon. Size: 6.5 cm (2.6 inches) x 5.1 cm (2.0 inches). Shell collected from the beach in the greater Cabo San Lucas area, Baja California Sur, November 2015. Collection, photography and identification courtesy of Bob Hillis, Ivins, Utah.

Thorn Latirus Shell, Opeatostoma pseudodon. Photographs taken in its native environment within Zihuantanejo Bay, Guerrero, March 2018 and December 2022, then released unharmed. Photograph courtesy of Ron Woheau, Zihuantanejo. Identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: The Thorn Latirus Shell, Opeatostoma pseudodon (Burrow, 1815), is a gastropod mollusk that is a member of the Fasciolariidae Family of Spindle, Horse Conchs and Tulip Shells. The genus Opeatostoma is one of sixty-eight genera in this family, and this is the only species in this genus. They are also known as the Banded Tooth Latirus Shell, the Long-tooth Latirus Shrll, the Red-footed Conch Shell, and the Zebra Toothed-snail Shell and in Mexico as Caracol Espinoso and Caracol de Pie Rojo  The species name pseudodon means false tooth and refers to this shell’s  tooth-like projection adjacent to the aperture.

Description: Thorn Latirus Shells are sturdy, with four or five whorls. They have a large body whorl, a moderately high spire with sloping sides, and a short open siphon canal. The exterior of the shell is sculpted with low spiral ridges. The aperture is large, quadrate, and its inner lip is sculpted with folds. A long tooth projects from the anterior end of the outer lip. The exterior of the shell is white and the ridges are dark brown to black. The interior is white.  The living animal has a red foot. Thorn Latirus Shells reach a maximum of 7.5 cm (3.0 inches) in length and 5.9 cm (2.3 inches) in height.

Habitat and Distribution: Thorn Latirus’ are found on rocks and occasionally on sand within in the intertidal zone, and to depths up to 41 m (135 feet). They are a subtropical to tropical Eastern Pacific Species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula and north of Gonzaga Bay, Baja California, in the Sea of Cortez.

Ecology and Behavior: Thorn Latirus’ are a poorly studied and understood species. There is very limited documentation related to their diet, predation, reproduction or ecosystem interactions. Other species in the Fasciolariidae Family are predatory carnivores that feed on barnacles, mollusks, and worms. They are gonochoric and reproduce sexually, with internal fertilization. The eggs are laid in protective capsules. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. 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.

Synonyms: Buccinum pseudodon and Monoceros cingulatum.