Regal Tellin Shell, Eurytellina regia

Regal Tellin Shell, Eurytellina regia, Left Valve. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2025. Size: 4.9 cm (1.9 inches) x 2.9 cm (1.2 inches) x 0.3 cm (0.1 inches)  Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Regal Tellin Shell, Eurytellina regia, Right Valve. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2025. Size: 4.6 cm (1.8 inches) x 2.7 cm (1.1 inches) x 0.5 cm (0.2 inches)  Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Regal Tellin Shell, Eurytellina regia (Hanley, 1844), is a member of the Tellinidae Family of Tellin Shells. The genus Eurytellina is one of one hundred four genera in this family, and there are eighteen species in this genus. In Mexico this species is called Tellina Regia. The taxonomy of this genus is debated, even among experts. Some sources still consider this species to be within the genus Tellina, with the proper scientific name being Tellina (eurytellina) regis.

Description: Regal Tellin Shells have an elongate oval to trigonal outline, with a rounded anterior and a truncate posterior. The exterior is sculpted with wide commarginal ribs and fine commarginal striations. This sculpting may not be present on the posterior third of the shell. These pretty shells  may be reddish, light pink, or (rarely) white in color, usually with lighter concentric bands. Some specimens display lighter radiating bands as well.  Regal Tellin Shells are distinguished from most other similar looking shells in the region by a raised strengthening rib on the interior, just posterior to the anterior adductor muscle scar. Though this trait is also shared by the Unevenly Striped Tellin Shell, Eurytellin inaequistriata. Regal Tellin Shells reach a maximum length of 5.2 cm (2.0 inches), which is considerably longer than the Unevenly Striped Tellin Shell which has a maximum length of 3.4 cm (1.3 inches).

Habitat and Distribution: Regal Tellin Shells are found in sand and mud substrates  within the intertidal zone to depths up to 24 m (79 feet).  They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean from Laguna Ojo de Libre, Baja California Sur south to Guatemala. They are found throughout the Sea of Cortez.

Ecology and Behavior: Regal Tellin Shells are suspension feeders that feed primarily on planktonic algae, and suspended detritus. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. These shells are generally considered to be rare. From a conservation perspective they have not been formally evaluated.

Synonyms: Tellina (Eurytellina) ecuadoriana, Tellina (Eurytellina) regia, Tellina ecuadoriana, and Tellina regia.