Saturn Keyhole Limpet Shell, Diodora saturnalis

Saturn Keyhole Limpet Shell, Diodora saturnalis. Shell collected off  the beach in the greater Los Cabos area, Baja California Sur, June 2019. Size: 2.5 cm (1.0 inch) x 1.5 cm (0.6 inches). Identification courtesy of Bob Hillis, Ivins, Utah.

The Saturn Keyhole Limpet, Diodora saturnalis (Carpenter, 1864), is a gastropod molluck that is a member of the Fissurellidae Family of Keyhole Limpets. They derive their name form their three-lobed keyhole that looks like a side view of the planet Saturn. These shells have a broad oval profile and are thicker and higher than most other Keyhole Limpets in the area. The exterior of the shell is sculpted by radial ribs that may extend to the margins as crenulations. The keyhole is relatively small and set toward the anterior margin. The exterior of the shell varies from gray, green, pink, reddish, tan or whitish with darker radiating bands; the interior is white with gray around the keyhole. The Saturn Keyhole Limpet Shells reach a maximum of 2.5 cm (1.0 inch) in length and 1.5 cm (0.6 inches) in height.

Saturn Keyhole Limpets are found attached to rocks within lagoons and around mangroves in the intertidal zone to depths up to 35 m (115 feet). They range from San Ignacio Lagoon, Baja California Sur, to Peru, including the Galapagos Islands and they are found throughout the Sea of Cortez.

A synonym is Glyphis saturnalis.