The frilled shark (Chlamydoselachus anguineus) is one of the most ancient-looking sharks alive — a deep-sea species so primitive in its anatomy that it is often called a “living fossil.” It has a long, eel-like body, a distinctively wide mouth at the front of its head (rather than underneath like most sharks), and 300 trident-shaped teeth arranged in 25 rows. It lives in deep oceanic waters worldwide at depths of 120–1,500 meters and is almost never seen alive at the surface. When it is encountered, the effect is startling — it looks less like a modern shark and more like something from the Cretaceous.
What Does a Frilled Shark Look Like?
The frilled shark is immediately recognizable — there is nothing else in the ocean quite like it. Key features:
- Body: Long, cylindrical, and eel-like — adults reach 1.5–2 meters in length. The body shape is unlike any other living shark.
- Head: Broad and flattened with a terminal mouth (at the very front, not underneath), giving it an appearance more like a moray eel than a typical shark.
- Gills: Six pairs of gill slits — most sharks have five. The first pair meets across the throat, forming a distinctive ruffled or “frilled” collar that gives the species its name.
- Teeth: 300 small, three-pronged (trident-shaped) teeth in 25 rows — designed for gripping slippery prey like squid and fish rather than cutting or crushing.
- Color: Dark brown to grey-brown throughout.
- Fins: Placed far back on the body, near the tail — another primitive feature that distinguishes it from modern shark families.
Why Is It Called a Living Fossil?
The frilled shark’s anatomy closely resembles fossil shark species from the Cretaceous and earlier periods — it has changed relatively little over tens of millions of years. Its six gill slits (most modern sharks have five), terminal mouth position, and overall body plan are considered primitive features retained from ancient shark lineages. The two living frilled shark species — Chlamydoselachus anguineus and the southern African Chlamydoselachus africana — are the only surviving members of their family, Chlamydoselachidae.
However, “living fossil” is an oversimplification — frilled sharks have continued to evolve, and their deep-sea lifestyle has insulated them from many of the selective pressures that drove dramatic changes in shallower-water shark lineages.
Where Do Frilled Sharks Live?
Frilled sharks inhabit deep oceanic waters across much of the world — they have a wide but patchy distribution in the Atlantic, Pacific, and Indian Oceans. Key areas where they have been recorded include:
- Off the coast of Japan (where most research specimens have been collected)
- Off southern Africa and Namibia (C. africana)
- The eastern Atlantic off Portugal, the British Isles, and Norway
- The eastern Pacific off California and Chile
- Australia (occasional trawl bycatch)
They are most commonly found between 200 and 1,000 meters depth, though they have been recorded as shallow as 50 meters at night when they ascend to feed, and as deep as 1,570 meters.
What Do Frilled Sharks Eat?
Frilled sharks are thought to feed primarily on cephalopods — squid and octopus — as well as deep-sea fish and smaller sharks. Their teeth are designed for snagging and holding slippery prey, not biting through large animals. Their unusually flexible jaw and jaws that can open to an extreme angle may allow them to consume prey close to their own body length.
One proposed hunting method — based on their body flexibility and jaw structure — is that they coil their body like a snake and lunge forward at prey, using their terminal mouth to seize squid head-on. This has not been directly observed but is consistent with their anatomy.
Frilled Shark Reproduction: The Longest Pregnancy of Any Vertebrate
Frilled sharks are ovoviviparous — embryos develop inside egg cases retained within the mother. Litter sizes are typically small: 2–12 pups. What makes frilled shark reproduction extraordinary is the estimated gestation period of approximately 3.5 years — the longest pregnancy of any vertebrate species on Earth. This estimate is based on embryo growth rates and tooth development data from specimens collected by fisheries, as live birth has never been observed.
This extremely slow reproduction means frilled shark populations recover very slowly from any mortality pressure — a significant conservation concern.
Conservation Status
The frilled shark is listed as Least Concern on the IUCN Red List — but this reflects data deficiency as much as confirmed abundance. They are caught as bycatch in deep-sea trawl fisheries and are occasionally targeted for liver oil. Because they live so deep and are rarely encountered, population trends are essentially unknown. Their extremely slow reproductive rate is a concern if bycatch mortality is higher than currently estimated.
Key Facts
- Scientific name: Chlamydoselachus anguineus
- Length: Up to 2 meters
- Depth range: 50–1,570 meters (typically 200–1,000 m)
- Diet: Squid, octopus, deep-sea fish, small sharks
- Teeth: 300 trident-shaped teeth in 25 rows
- Gill slits: 6 pairs (most sharks have 5)
- Gestation: ~3.5 years — longest of any vertebrate
- Conservation status: Least Concern (IUCN)
Frequently Asked Questions
Has a frilled shark ever attacked a human?
No. Frilled sharks live at depths far below where humans swim or dive without submersibles. There are no recorded attacks on humans. They are not aggressive animals — they feed on squid and small fish, not large prey.
How rare is it to see a frilled shark?
Extremely rare. Live surface sightings are almost unheard of. Most known specimens have been collected as deep-sea trawl bycatch. The few live individuals brought to the surface or encountered by submersibles typically die quickly due to pressure and temperature changes. A live frilled shark was filmed off the Algarve coast of Portugal in 2004 — it remains one of the most cited live footage examples.
Is the frilled shark related to the megalodon?
No. Megalodon was a massive mackerel shark related to great whites. The frilled shark belongs to a completely different and much older lineage — Chlamydoselachidae. Their resemblance to prehistoric sharks reflects independent retention of primitive features, not close evolutionary relationship.
How long have frilled sharks existed?
The frilled shark family Chlamydoselachidae has a fossil record dating back approximately 95 million years. The living species’ lineage is ancient, though the exact age of the modern species is uncertain. They are among the oldest surviving shark lineages still living today.