Conspicuous Chiton Shell, Stenoplax conspicua
Conspicuous Chiton Shell, Stenoplax conspicua. Chiton collected offshore San Diego, California, October 2003. Size: 8.6 cm (3.4 inches) x 4.4 cm (1.7 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.
Phylogeny: The Conspicuous Chiton, Stenoplax conspicua (Dall, 1879), is a member of the Ischnochitonidae Family of Chiton Shells. The genus Stenoplax is one of twelve genera in this family, and there are twenty-four species in this genus.
Description: Conspicuous Chitons obtain their common name from their large size when compared to other chitons. They have an elongated oval profile, with the length being about twice the height. Their dorsal surface has a fairly high arch, and the edges of the plates are marked with fine radial and concentric ridges. The plates are gray-green in color, except in the center of the shell, where the outer layer has normally worn away and a pinkish under-layer is visible. The girdle is grayish green and covered with short hair-like scales, which give it a velvety feel. The Conspicuous Chiton Shell reach a maximum of 9.5 cm (3.7 inches) in length and 4.8 cm (1.9 inches) in height.
Habitat and Distribution: Conspicuous Chitons are found on rocks that are surrounded by sand. They live intertidally, and to a depth of 3 m (10 feet). Some sources extend the maximum depth to 30 m (100 feet). During the day these shells usually hide under rocks or bury themselves in the sand or small pebbles. The Conspicuous Chiton emerge at night to feed. They are a temperate Eastern Pacific species that are found on a limited basis in Mexican waters of the Pacific Ocean ranging from north of Guerrero Negro, Baja California, along the central and northwest coasts of the Baja Peninsula. Some sources place them as far south as the Cape Region of Baja California Sur and into the Sea of Cortez.
Ecology and Behavior: Conspicuous Chitons are grazers that feed primarily on algae, which they scrape from the rock with their radula. They are gonochoric and reproduce sexually, through broadcast spawning. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Conspicuous Chiton 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: Ischnochiton (Stenoradsia) conspicuus, Ischnochiton (Stenoradsia) conspicuus var. solidus, Ischnochiton conspicuus, Ischnochiton sarcosus, Maugerella conspicua, Stenoplax (Maugerella) conspicua, and Stenoplax (Stenoradsia) conspicua.