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

The Thorn Latirus, Opeatostoma pseudodon (Burrow, 1815), is a gastropod mollusk that is a member of the Fasciolariidae Family of Spindle, Horse Conchs and Tulips. They are also known as the Banded-tooth Latirus. The shell is sturdy with four or five whorls with a large body whorl, a moderately high spire with sloping sides, a short open siphon canal, and a large aperture that has an inner lip marked with a few folds. A long tooth projects from the anterior end of the outer lip. The exterior of the shell is white, marked by numerous dark brown, low spiral ridges; the interior is white. The Thorn Latirus Shells reach a maximum of 7.5 cm (3.0 inches) in length and 5.9 cm (2.3 inches) in height.

Thorn Latirus are found attached to and under rocks and occasionally on and within sand substrate in the intertidal zone to depths up to 41 m (135 feet). They range from Gonzaga Bay, Baja California in the Sea of Cortez, to Peru, including the Galapagos Islands. They have not been documented from coastal waters of the west coast of Baja.

Synonyms are  Buccinum pseudodon and Monoceros cingulatum.