Armored Drill Shell, Murexsul armatus

Armored Drill Shell, Murexsul armatus. Shell collected off the beach of Punta Chivato, Baja California Sur, June 2025. Size: 3.3 cm (1.3 inches) x 1.9 cm (0.7 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Armored Drill Shell, Murexsul armatus. Shell collected off the beach of Punta Chivato, Baja California Sur, June 2025. Size: 3.6 cm (1.4 inches) x 2.3 cm (0.9 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Phylogeny: The Armored Drill Shell, Murexsul armatus (A. Adams, 1854) is a member of the Muricidae Family of Rock Shells, and of the Aspellinae Subfamily. The Murexsul Genus is one of twenty-three genera in the Aspellinae Subfamily The genus Murexsul contains eighty-three species. They are known in as Murex Armado.

Description: The Armored Drill Shell is fusiform (spindle-shaped) and consists of around 5 whorls. The spire is relatively high, with the top of the body whorl located midpoint on the shell. The exterior has a scaly texture. The shell is sculpted with strong, spiny, axial ribs. The spines are most prominent at the shoulder. The aperture is small and irregularly shaped. The anterior canal is long and open. Armored Drill Shells are yellowish-white in color. Armored Drill Shells reach 2.5 cm (1 inch) in length.

Habitat and Distribution: Armored Drill Shells are generally found on, and under, rocks. They live in the intertidal zone and to a depth of about 35 m (115 feet). Armored Drill Shells are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean witih the exception that they are absent from north of Magdalena Bay, Baja California Sur along the central and northwest coasts of the Baja Peninsula and north of north as Punta Colorada, Sonora, in the Sea of Cortez.

Ecology and Behavior:  Armored Drill Shells are a poorly researched and documented species. Little is known regarding their diet, predation, and ecosystem interactions. They are carnivorous predators, but their diet has not been documented. Other similar species prey on bivalves, small invertebrates, and eggs. Other similar species are preyed upon by crabs, fish, sea stars, gastropods, and shore birds. They are gonochoric and reproduce sexually, through broadcast spawning, with internal fertilization. The eggs are laid in protective capsules. Their engagement in any type of parasitic, commensal or mutualistic relationship has not been formally documented. From a conservation perspective the Armored Drill Shell has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.

Synonyms: Murex armatus, Muricopsis armatus, and Muricidea dubius var. squamulatus.