Obelisk Murex Shell, Dermomurex obeliscus

Obelisk Murex Shell, Dermomurex obeliscus. Shell provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, March 2014. Size: 2.3 cm (0.9 inches) x 1.0 cm (0.4 inches).

Phylogeny: The Obelisk Murex, Dermomurex obeliscus (Adams, 1853), is a gastropod mollusk that is a member of the Muricidae Family of Rock Shells.  The genus Dermomurex is one of one hundred ninety-eight genera in this family, and there are fifty-two species in this genus. In Mexico this species is called Murex Obelisco.

Description: The Obelisk Murex derives its name from its obelisk-shaped profile, that is, it has relatively straight sides that rise to a pyramidal top. These shells always appear to be worn and eroded. They have five to six whorls and a tall blunt spire. The varices are low and rounded.  The siphon canal is relatively small, short, curved, and open. The exterior of the shell is white to light tan, with numerous, narrow, reddish-brown, spiral lines. Obelisk Murexes reach a maximum of 3.3 cm (1.3 inches) in length and 1.4 cm (0.6 inches) in height.

Habitat and Distribution: Obelisk Murexes are found on rocks, intertidally, and to an unknown depth. They are a tropical Eastern Pacific species. In Mexican waters they have a known range from Guaymas, Sonora to Guatemala. The shell photographed above was collected in the greater Todos Santos area of Baja California Sur indicative that it is a resident of the west coast waters of Baja California Sur.

Ecology and Behavior: Obelisk Murexes are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. Other species in Family Muricidae are predators that feed primarily on shelled invertebrates. They are gonochoric and reproduce sexually,  with internal fertilization.  There is no mention in the available literature of them engaging in any types of parasitic, commensal, or symbiotic relationships. From a conservation perspective they have not been formally evaluated.

Synonyms:  Dermomurex (Dermomurex) obeliscus, Murex (Ocinebra) obeliscus, and        Murex obeliscus.