Chlamydoselachus

Chlamydoselachus is a genus of sharks in the family Chlamydoselachidae, order Hexanchiformes. It includes the living frilled shark (Chlamydoselachus anguineus) and several extinct species known from the fossil record. The lineage is ancient, with fossils dating back to the Middle Jurassic, making it one of the most primitive extant shark lineages.

Members of Chlamydoselachus have elongated, eel-like bodies, a relatively small head, very small eyes, and long jaws bearing multiple rows of slender teeth. The most distinctive feature is the six pairs of long gill slits that extend around the throat, producing a frilled appearance from which the common name derives. The fins are small, with dorsal fins positioned far back on the body. Individuals typically have a dark, muted coloration.

Size varies, but individuals commonly reach about 1.5 to 2 meters in length, with maximum sizes reported near or above 2 meters. They inhabit deep-sea environments and are found in temperate and tropical oceans worldwide, including parts of the Atlantic, Pacific, and Indian Oceans. They occur at depths ranging from several hundred meters to well below a thousand meters, often in continental shelf and slope regions.

Ecology and life history: frilled sharks are presumed to be slow-moving, long-lived, and solitary. Their diet consists of small fish and cephalopods. Reproduction is believed to be ovoviviparous, with internal fertilization and relatively few offspring, though the deep-sea lifestyle means details are poorly known.

Conservation: data on population trends are limited due to the species’ deep-water habitat. They are not targeted by major fisheries, but bycatch in deep-sea operations can pose localized threats.