Frilled Shark

The Frilled Shark is a primitive, eel-like deep-sea species often referred to as a living fossil due to its retention of ancestral shark features found in the fossil record. It is the most widespread member of family Chlamydoselachidae, found in deep waters across the Atlantic and Pacific Oceans. Adults typically reach 1.5-2 meters. Its snake-like body and unusual frilled gill slits distinguish it sharply from typical sharks, reflecting its deep evolutionary lineage. It is currently assessed as Least Concern, though data remain limited given its rarity and remote deep-sea habitat, with most records coming from incidental deep trawl catches.

• Elongated, eel-like or serpentine dark brown to gray body
• Six pairs of frilly, fringed gill slits running along the throat, the first pair meeting across the throat
• Wide, flattened head with a large mouth positioned terminally rather than underslung
• Numerous small, needle-like, backward-curving teeth arranged in many rows
• Single dorsal fin positioned far back near the tail, opposite the anal fin The combination of an eel-like body, frilled gill slits, and a single far-back dorsal fin is unlike any other living shark, making identification straightforward when specimens are observed.

Frilled Sharks inhabit deep continental slope and outer shelf waters worldwide, typically at depths between 120 and 1,280 meters, though most commonly encountered around 500-1,000 meters. Records span the eastern Atlantic, western Pacific including Japan, and scattered locations off Africa, Australia, and South America. They favor cold, dark mesopelagic to bathyal waters, occasionally moving to shallower depths, which has led to rare live surface sightings that generated significant public and scientific interest given the species' otherwise elusive deep-sea existence.

Frilled Sharks are believed to be relatively sluggish, eel-like swimmers that use body undulation for propulsion, though they may be capable of rapid strikes when capturing prey. Diet consists mainly of squid, along with smaller fish and other sharks, with numerous backward-curving teeth well suited to gripping soft-bodied cephalopod prey and preventing escape. Reproduction is ovoviviparous with an exceptionally long gestation period, estimated at up to three and a half years, among the longest documented for any vertebrate. Their deep, remote habitat and unusual anatomy have made close behavioral observation extremely rare.