There are over 500 species of shark in our planet’s oceans, and nature has produced an astonishingly wide variety of these incredible creatures. Some are familiar to the general public, while others are rare, relatively unknown, and often especially strange and weird looking.
Like many of the oddest-looking sea creatures, the incredible frilled shark spends most of its time in the deep sea, close to the ocean floor. With a depth range of between 50–1,570 meters (160–5,150 feet), this isn’t an animal you’ll see cruising the coral reefs as you snorkel on your next vacation.
Life in the depths is very different from that in shallower waters, and creatures like the frilled shark need to be able to cope with the challenging conditions.
We’re going to look at one of the oddest-looking sharks around. In fact, the frilled shark’s appearance is so unusual and primitive it’s often referred to as a “living fossil.”
Let’s find out why.
What Do Frilled Sharks Look Like?
The frilled shark doesn’t like a typical shark in almost every way possible.
In appearance, this deep sea throwback has an eel-like (anguilliform) shape, so to many people, it looks more like a snake than a shark.
While other sharks have evolved through the millennia, the primitive frilled shark has more in common with its Carboniferous period family roots than it does with the sharks we’re familiar with today.
Frilled sharks get their common name from the six pairs of gill slits that form a distinctive fringed frill around its neck at the front of the throat, like a collar.
The body has a dark-chocolate brown, brownish-grey, or brownish-black color, and the shark’s dorsal, pelvic, and anal fins are all located towards the rear of the smooth, elongated body, enhancing the snake or eel-like appearance.
Underneath the body, running the entire length of the belly, the shark has a pair of thick skin folds separated by a groove. Experts do not know if these serve any function today or if they’re some evolutionary remnant long since become redundant.
It could be simply that they allow for expansion when the shark is digesting a substantial meal.
The frilled shark has a flat head with a short nose. The large mouth is set at the tip of the head (terminal) rather than being located underneath, as is more usual for sharks.
Finally, large, deep-set, and horizontally oval eyes lacking the normal protective nictitating membrane third-eyelid, and vertical nose slits complete the snake-like appearance.
The Frilled Sharks Unique Teeth
If the frilled shark’s frills, head, and body weren’t enough to make it stand out, this deepsea creature becomes scarily unforgettable when you see inside its mouth.
It can open extremely wide (just like a snake’s) to swallow large prey, and inside there are widely spaced rows of more than 300 trident-shaped spiky teeth.
These triple-pointed teeth are some of the most interesting and uniquely shaped of any shark. They have an interesting backward curve shape that doesn’t seem to allow for aggressive biting.
Instead, marine biologists believe that the shark uses them to catch and hold squid and other soft-bodied prey before deftly swallowing them whole.
Two Different Frilled Shark Species
There are actually two different species known as frilled sharks in the Chlamydoselachus family. The originally discovered frilled shark (Chlamydoselachus anguineus) and the more recent addition, the southern African frilled shark (Chlamydoselachus africana).
The sharks look and act more or less identically, so we can treat them the same for our purposes.
However, it’s worth knowing that compared to C. anguineus, the southern African frilled shark has a somewhat shorter head with a wider mouth, longer gill slits, longer pectoral fins, and a shorter spinal column containing fewer vertebrae (147 vs. 160-171).
Frilled Shark Taxonomy
As we mentioned, there are two known species of frilled shark: The frilled shark and the southern African frilled shark.
The full scientific description is as follows:
Kingdom – Animalia
Phylum – Chordata
Class – Chondrichthyes (Cartilaginous Fish)
Order – Hexanchiformes (proposed to move to the unique order Chlamydoselachiformes)
Family – Chlamydoselachidae
Genus – Chlamydoselachus
Species – anguineus or africana
Other Common Names – The “lizard shark” and the “scaffold shark.”
When was the frilled shark discovered? The frilled shark was first discovered in Japan between 1879 and 1881 by the zoologist Ludwig Döderlein.
Unfortunately for him, Döderlein managed to lose his research manuscripts, so it was the zoologist Samuel Garman who published the first taxonomic description of the frilled shark in 1884 from a 1.5 meter (4 ft 11 in) long female found in Sagami Bay, Japan.
The scientific name Chlamydoselachus anguineus comes from the Greek word for frill and shark (chlamy and selachus) and the Latin for “like an eel” (anguineus).
The second species, the southern African frilled shark, was described in 2009 by marine biologists who found it in the Atlantic Ocean off the coast of south Angola and Namibia.
Frilled sharks were placed in the order Hexanchiformes (which means “six gills”), and they share the main features of having either six or seven pairs of gills, no nictitating membrane in the eyes, and only one dorsal fin.
However, the two living frilled sharks are very different from the five cow sharks that make up the rest of the order and may actually pre-date the other Hexanchiformes. Accordingly, ichthyologists have proposed moving them to a unique taxonomic order – Chlamydoselachiformes.
How Old is The Frilled Shark?
The frilled sharks around today have barely changed in 95 million years. Frilled sharks are often referred to as “living fossils” as they’re believed to be more or less the same as they were in the Late Cretaceous period.
Frilled Shark Characteristics
How Big is a Frilled Shark?
Frilled sharks are believed to grow to a maximum length of about 2 meters (6.5 feet) which matches the largest female specimen ever found. The largest male recorded was 1.7 meters (5.6 feet) in length.
Newly born juvenile frilled sharks are thought to be about 40–60 cm (16–24 in) long.
How Fast Can a Frilled Shark Swim?
The fastest sharks in the ocean don’t need to be concerned. The frilled shark isn’t going to win any underwater races with its estimated maximum speed of less than 5 mph (8 kph).
However, while they might not be that quick at swimming, frilled sharks can move with ease thanks to their excellent buoyancy control and flexible bodies.
Frilled sharks have light cartilaginous skeletons and large livers full of low-density lipids, which means that, unlike many other sharks, they don’t have to swim continually to stay afloat.
The sharks swim slowly and use their tails for propulsion by curling and coiling their bodies (much like a snake) in the appropriate direction.
Frilled Shark Life Cycle
Frilled sharks are ovoviviparous, meaning that the young are born from encapsulated eggs held inside the mother’s body.
After growing as embryos within the egg capsules, the baby sharks hatch inside the uterus when they reach 6–8 cm (2.4–3.1 in) long.
They will feed on the yolk sack, and possibly receive secretions from glands in their mother’s womb, and develop at an average rate of 1.40 cm (0.55 in) per month.
The young frilled sharks are eventually released as independent live pups of 40–60 cm (16–24 in) long after an astonishingly long gestation period of about 3.5 years – considered the longest of any vertebrate.
The average litter size is six pups, but it can be as few as two and as many as 15.
Not much is known about the reproductive process between the male and female frilled shark, as it hasn’t been witnessed. The shark is solitary, and it’s thought that they only come together to mate, perhaps gathering in large numbers around seamounts.
Experts consider that the female shark reaches sexual maturity at around 1.35-1.5 meters (4.4-4.9 feet), while for males, it’s when they get to 1-1.2 meters (3.3-3.9 feet)
The sharks don’t seem to have a regular breeding season, unlike many other animals. This is thought to be due to the reasonably constant water temperatures at the depths that the frilled sharks inhabit.
While it is not certain, it’s generally believed that the average frilled shark’s lifespan is about 25 years.
Where Do Frilled Sharks Live?
Frilled sharks spend most of their time close to the ocean floor on the outer continental shelf and the upper-to-middle continental slope in water temperatures below 15 °C (59 °F).
They have a wide distribution around the world focused in isolated, biologically productive areas in both the Atlantic and Pacific Oceans, including:
Eastern Atlantic
- Northern Norway
- Northern Scotland
- Western Ireland
- West coast of Europe from France to Morocco
- Madeira
- Mauritania in northwest Africa
Central Atlantic
- From north of the Azores islands to the Rio Grande Rise, off southern Brazil
- The Vavilov Ridge, off West Africa
Western Atlantic
- New England and Georgia, in the US
- Suriname
Western Pacific Ocean
- The Mariana Trench
- Southeastern Honshu, Japan
- Taiwan
- China
- New South Wales, Australia
- Tasmania
- New Zealand
Central and eastern Pacific Ocean
- Hawaii
- California
- Northern coast of Chile
The more recently discovered southern African frilled shark has been found off South Africa, Namibia, and southern Angola.
The typical water depth the frilled shark lives in depends on the location. For example, in Japan, the shark is found at 50–200 meters (160–660 feet), except for between August and November, when the shark will venture deeper to find cooler water.
The deepest that a frilled shark has ever been caught at was 1,570 meters (5,150 feet), but it’s generally thought that the usual maximum is around 1,000 meters (3,300 feet).
However, the shark doesn’t spend all its life in incredibly deep water. They practice diel vertical migration at night to feed considerably closer to the ocean’s surface.
Frilled Sharks Behavior
Frilled sharks live reasonably mysterious lives, and scientists don’t know much about their behavior in the ocean’s depths.
It’s thought that they’re solitary, except when it’s time to mate, and they appear reasonably peaceful and slow-moving, except when it’s time to catch their food.
Humans rarely come into direct contact with frilled sharks due to the extreme depths they usually live in.
Almost all encounters have been made from submersible vehicles, except for rare occasions where divers or anglers have come across a sick specimen in shallower waters.
What Do Frilled Sharks Eat?
The frilled shark leaves the deep water at night and travels to the shallows to hunt.
Scientists investigating the stomachs of captured specimens have found bony fish, smaller sharks, and cephalopods, typically squid (about 60 percent of its diet). Often sharks have been found with empty stomachs, which could mean that they eat only infrequently.
To find its prey, the frilled shark will use its sensitive lateral-line organ system to detect changes in pressure that indicate movement in the surrounding water. As the shark isn’t a fast swimmer, they’re thought to look for sick or injured animals that will be weaker and easier to catch.
Although it’s never been caught on camera, it’s thought that the shark probably hunts with its mouth open and may even use its bright white teeth as a lure to attract its prey. The shark may also rapidly open its large mouth to suck nearby food into the grasp of its trident teeth.
Once trapped, the rearward-facing teeth mean that prey has no opportunity to escape, as to release themselves, they’d need to swim further into the shark’s mouth.
However, not all meals involve a trip upwards, as the shark will likely also use its sense of smell to seek out carrion that’s drifted down from the surface.
What Hunts Frilled Sharks?
Larger sharks are probably the only thing that generally hunts frilled sharks.
Frilled sharks are killed by humans, typically accidentally, as commercial fishing by-catch. They’re not usually eaten but will be processed as fishmeal for animal feed.
Frilled sharks are regarded as a species of “least concern” on the IUCN Red List thanks to their wide distribution range in countries that practice effective fisheries management.
However, the list notes that the shark has an ”apparent rarity and intrinsic sensitivity to over-exploitation” that make ongoing studies necessary “to ensure this species does not become threatened in the near future.”
The question of “how many frilled sharks are left?” cannot be answered based on the current research. The Red List states, “there is no information available on the population size or trends. It is generally rare, but there are a few localities (for example, Japan) where it is more common.”
Conclusion
The frilled shark is a genuine “living fossil” closer to the sharks from millions of years ago than anything swimming in today’s seas.
With its prehistoric appearance, and largely unknown lifestyle, this deep sea creature might not be as famous as its shallow-water cousins, but it’s still one of the most fascinating animals in the world.
British-born Dan has been a scuba instructor and guide in Egypt's Red Sea since 2010.
Dan loves inspiring safe, fun, and environmentally responsible diving and particularly enjoys the opportunity to dive with sharks or investigate local shipwrecks.
When not spending time underwater, Dan can usually be found biking and hiking in Sharm's desert surroundings.