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.  They are known in Mexico as Murex Obelisco.

Description: The Obelisk Murex Shell has an obelisk-shaped profile, for which it is named, 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 with the intertidal zone to unknown depths. They are a tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula and north of Guaymas, Sonora, in the Sea of Cortez.

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 the Muricidae Family are predators that feed primarily on shelled invertebrates. They are gonochoric and reproduce sexually, with internal fertilization. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Obelisk Murex has not been formally evaluated.

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