Panamanian Hoof Shell, Antisabia panamensis

Panamanian Hoof Shell, Antisabia panamensis. Shell provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, April 2009. Size: 2.5 cm (1.0 inch) x 1.1 cm (0.4 inches).

Panamanian Hoof Shell, Antisabia panamensis. Shell collected off the beach in greater Loreto area, Baja California Sur, February 2025. Size: 7.1 cm (2.8 inches) x 5.8 cm (2.3 inches). Collection courtesy of Carol J. Snow, Del Mar, California.

Phylogeny: The Panamanian Hoof Shell, Antisabia panamensis (C.B. Adams, 1852), is a gastropod mollusk that is a member of the Hipponicidae Family of Hoof Shells. The genus Antisabia is one of eight genera in this family, and there are four species in this genus. They are also known as the Pacific White Horse Hoof.

Description: The Panamanian Hoof Shell shell has a circular to oval outline. The apex is located close to the posterior margin and may overhang the margin. The apex is often heavily eroded in adult specimens. The exterior of the shell can vary from smooth to rough layered. They have a brown periostracum. The exterior of the shell is white, often with a light pink or brown wash. The interior is white and smooth. Panamanian Hoof Shells reach a maximum of 7.1 cm (2.8 inches) in length and 5.8 cm (2.3 inches) in height established by the shell photographed above. The males are slightly smaller than the females

Habitat and Distribution: Panamanian Hoof Shells are found on, and under rocks, or attached to other shells. They are usually found in groups, with many males surrounding a few females. Once they attach to a substrate, they are fixed in that location. They live from the intertidal zone to depths up to 525 m (1,720 feet). They are a temperate and tropical Eastern Pacific species. In Mexican waters they are found along the entire west coast, including the entire Gulf of California.

Ecology and Behavior:  Panamanian Hoof Shells feed primarily on organic fragments, detritus, and pieces of algae. Because they are sedentary, they use their extendable snout to reach food sources and are dependent on water movement to bring them food. They are sequential hermaphrodites, beginning life as males and transitioning into females. They reproduce sexually, through broadcast spawning. The eggs sacs are brooded under the female’s shell. Beyond their sometimes being an epibiont on other shells, 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 wide distribution and should be consider to be of Least Concern.

Synonyms: Hipponix fimbriata, Hipponix panamensis, Hipponix serratus, and Hipponyx panamensis.