Solander’s Trivia Shell, Pusula solandri

Solander’s Trivia Shell, Pusula solandri. Shell collected off the beach of Bahía Concepción, Baja California Sur, October 2019. Size: 1.6 cm (0.6 inches) x 1.2 cm (0.5 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny: Solander’s Trivia Shell, Pusula solandri (J. E.Gray, 1832), is a gastropod mollusk that is a member of the Triviidae Family of Trivia Shells. The genus Pusula is one of sixteen genera in this family, and there are eight species in this genus. They are also known as the False Cowry Shell, the Sea Button Shell and Solander’s Coffee-bean Shell and in Mexico as  Trivia de Solander.

Description: Solander’s Trivia Shells are coffee bean-shaped. They have an internal spire. The central ribs end in knobs at the furrow on the dorsal apex of the body whorl. The aperture is fairly straight and toothed on both lips. They are a light brown or light gray in color and some have a pinkish tinge; the central ribs end in lighter colored knobs. When actively feeding the mollusk’s soft mantle sides emerge and join together at the mid-line of the back. The exposed mantle is soft gray with warty brown bumps. Solander’s Trivia Shells reach a maximum of 2.2 cm (0.9 inches) in length and 1.6 cm (0.6 inches) in height. Solander’s Trivial is very similar to the Coffee Bean Shell, Pusula californiana (smaller, purplish,  with ribs that  cross the midline).

Coffee Bean Shell, Pseudopusula californiana, on the right, versus Solander’s Trivia Shell, Pusula solandri. Photograph courtesy of Bob Hillis, Ivins, Utah.

Solander’s Trivia Shells can also be easily confused with the Radiant Button Shell or Radiating Trivia Shell, Trivia radians (lighter in color and larger).

Habitat and Distribution: Solander’s Trivia reside attached to, and under, rocks in the intertidal zone, and to depths up to 35 m (115 feet). They are most commonly found as dead specimens washed up on the beach. They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean.

Ecology and Behavior: Solander’s Trivias are predators that feed primarily on ascidians. They are gonochoric and reproduce sexually. 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  wide distribution and should be considered to be of Least Concern.

Synonyms: Cypraea solandri, Pasula padreserrai, and Trivia solandri.