Donkey Thorn Oyster Shell, Spondylus limbatus

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell provided by the commercial fishermen of the greater Los Cabos area, March 2014. Size: 5.8 cm (2.3 inches) x 5.3 cm (2.1 inches).

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2026. Size: 6. 1 cm (2.4 inches) x 6.8 cm (2.7 inches) x 1.1 cm (0.4 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2026. Size: 6.5 cm (2.6 inches) x 5.6 cm (2.2 inches) x 1.0 cm (0.4 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2026. Size: 12 cm (4.7 inches) x 12 cm (4.7 inches) x 4.3 cm (1.7 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2026. Size: 13 cm (5.1 inches) x 10 cm (3.9 inches) x 6.2 cm (2.4 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Donkey Thorn Oyster Shell, Spondylus limbatus. Shell collected off the beach at Punta Chivato, Baja California Sur, April 2026. Size: 20 cm (7.9 inches) x 18 cm (7.1 inches) x 6.5 cm (2.6 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny: The Donkey Thorn Oyster, Spondylus limbatus (G.B. Sowerby, II, 1847), is a bivalve mollusk that is a member of the Spondylidae Family of Spiny Oyster Shells. Spondylus is the only genus in the Spondylidae Family, and there are seventy-five species in the genus. This species is also known as the Cat’s Tongue Oyster Shell and they are known in Mexico as Almeja Burra, Callo Escarlopa and Ostra Espinosa Burricais.

Description: The Donkey Thorn Oyster Shell is solidly built and oval shaped. The external surface has radiating lines with short spines; in older individuals the spines may be worn down. The exterior of the shell maybe reddish, purple, yellow, or orange, but never white. The interior marginal color band matches the exterior color. The Donkey Thorn Oyster shell  reaches a maximum of 25 cm (9.7 inches) in length and 21 cm (8.3 inches) in width.

Habitat and Distribution: Donkey Thorn Oysters are found attached to solid substrates from the intertidal zone to depths up to 53 m (175 feet). They are subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from north of San Alijo Rocks, Baja California Sur, along the central and northwest coasts of the Baja Peninsula and north of San Felipe, Baja California, in the Sea of Cortez.

Ecology and Behavior:  Donkey Thorn Oysters are suspension feeders that feed primarily on planktonic algae and suspended organic matter. They are gonochoric and reproduce sexually, through broadcast spawning, with external fertilization. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Donkey Thorn Oyster has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Spondylus calcifer, Spondylus coccineus, Spondylus lamarckii, Spondylus punicus, Spondylus radula, and Spondylus smithii.