CLOSE

11 Fascinating Facts About the Frilled Shark

Sometimes called a “living fossil” because it has changed so little since prehistoric times, the eel-like frilled shark—which is rarely seen by humans—has been in the news this week after a snake-like one was found off the coast of Portugal. Here’s a quick primer.

1. IT’S NAMED FOR ITS GILLS.

Its scientific name is Chlamydoselachus anguineus, but this creature’s common name comes from its gills: Unlike all other sharks, which have separate gills, C. anguineus’ first pair of gills go all the way across its throat; each pair is lined at the edges with red “fringe.”

2. IT WAS DISCOVERED IN THE 19TH CENTURY.

The sharks were first scientifically described by German ichthyologist Ludwig H.P. Döderlein, who taught at Tokyo University from 1879 to 1881 and brought two specimens captured in Tokyo Bay when he returned to Vienna. His paper describing the sharks was lost, however, so the first description comes from Samuel Garman in the 1884 edition of the Bulletin of Essex Institute. In the remarks after the description, Garman noted that

Such an animal as that described is very likely to unsettle disbelief in what is popularly called the “sea serpent.” Though it could hardly on examination be taken for anything but a shark, its appearance in the forward portion of the body, particularly in the head, brings vividly to mind the triangular heads, deep-cleft mouths, and fierce looks of many of our most dreaded snakes. In view of the possible discoveries of the future, the fact of the existence of such creatures, so recently undiscovered, certainly calls for a suspension of judgment in regard to the non-existence of that oft-appearing but elusive creature, the serpent-like monster of the oceans.

The frilled shark’s species name, anguineus, is Latin for “consisting of snakes” or “snaky.”

Biologist David A. Ebert, director of the Pacific Shark Research Center, described a second frilled shark species—Chlamydoselachus africana, which lives off the coast of Africa and is about half as long as its predecessor—in 2009.

3. IT’S GOT INSANE TEETH.

The frilled shark’s mouth is just as terrifying as the maw of a great white: It’s lined with 25 rows of backward-facing, trident-shaped teeth—300 in all. “The teeth are constructed for grasping and from their peculiar shape and sharpness it would seem as if nothing that once came within their reach could escape them,” Garman wrote. “Even in the dead specimen the formidable three-pronged teeth make the mouth a troublesome one to explore.” 

Ebert can testify to that fact. “I can tell you from snagging my fingers on the teeth, you can only back out one way and that’s in toward the mouth and then out,” he told WIRED. “It didn’t feel good, I can tell you that.” The shark uses the bright white teeth, which sharply contrast against its brown body, to lure in prey: “By the time [the prey] realize, Oh, that’s the teeth of a shark, they’re too close and the shark is able to ambush them at that point,” Ebert said. “It’s almost like when you drive out of a parking lot exit and they have the spikes sticking out that say, ‘Do not back up.’ That’s kind of what happens when these things catch prey items.”

And as if its teeth weren’t freaky enough, the frilled shark has spines, called dermal denticles, lining its mouth. So if you happen to see one of these anywhere, it’s better to look and not touch.

4. IT “HOVERS” IN THE WATER...

Scientists once believed that the frilled shark wriggled through the water like an eel. But according to the ReefQuest Centre for Shark Research, “its body cavity is elongate and packed with a huge liver perfused with low-density oils and hydrocarbons, making the shark almost neutrally buoyant at depth.”

5. … AND IT MAY STRIKE AT ITS PREY LIKE A SNAKE.

No one has ever observed the frilled shark hunting, but scientists believe that it uses its posterior fins as propulsive surfaces to launch itself at its prey. Its long jaws, which terminate at the back of its head, may allow the animal to gape extra wide and take in prey half as long as its body. Analysis of the stomach contents of captured specimens has revealed that the frilled shark’s diet is 61 percent cephalopod, 11 percent teleost fishes, and, occasionally, other sharks.

6. IT’S FOUND ALL OVER THE WORLD—BUT YOU PROBABLY WON’T SEE IT.

The Food and Agriculture Organization of the United Nations notes that the frilled shark is “wide-ranging but spottily distributed”; you can see where the shark is found on the map above. It typically resides in depths between 390 and 4200 feet, so people rarely see these sharks unless they venture to the surface, which isn’t unheard of (as you’ll see below).

7. FEMALES ARE BIGGER THAN MALES.

On average, males range from 3.2 to 3.6 feet and females from 4.4 to 4.9 feet; the maximum these sharks can reach is 6.4 feet.

8. THEIR GESTATION PERIOD MAY BE 3.5 YEARS LONG.

A study of frilled sharks in Japan revealed that the animals breed year-round; litters typically consist of six pups, which emerge from eggs while still in the mother’s uterus and are then born live. Scientists think the shark may have the longest gestation period ever: Frilled sharks could gestate for as long as 42 months, nearly twice as long as African elephants carry their young. Scientists theorize that the extreme length has something to do with the shark’s cold deep sea habitat.

9. IT WASN’T SEEN IN ITS NATURAL HABITAT UNTIL 2004.

NOAA scientists exploring the “Latitude 31-30 Transect” in the Atlantic Ocean captured a video of a frilled shark “swimming over sea bottom that was covered with tiny sand dunes” during a submersible dive. “This species has been, on rare occasion, caught or taken in bottom trawls,” the site notes. “To the knowledge of everyone on board, however, this was the first time anyone had ever seen the rare species in its natural habitat.”

10. ONE WAS CAPTURED IN JAPAN IN 2007.

In January 2007, a Japanese fisherman spotted a strange, eel-like creature with a mouth full of sharp teeth near the surface; he alerted the staff of the Awashima Marine Park in Shizuoka, who captured the animal and transferred it to a seawater pool, where they filmed it. “We think it may have come close to the surface because it was sick, or else it was weakened because it was in shallow waters,” a park official said. “We believe moving pictures of a live specimen are extremely rare. They live between 600 and 1000 meters under the water, which is deeper than humans can go.” The shark, a female, died a few hours after its capture.

11. IT CALLS ANOTHER FREAKY SHARK ITS COUSIN.

The frilled shark might have rows upon rows of gnarly teeth, but its cousin, the goblin shark, can thrust its jaw out of its face. Which is more terrifying?

nextArticle.image_alt|e
iStock
arrow
Big Questions
Why Do Cats 'Blep'?
iStock
iStock

As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out
iStock

If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

nextArticle.image_alt|e
John James Audubon, Wikimedia Commons // Public Domain
arrow
Animals
10 Tragic Stories of Extinct Animals
Drawing depicting the Great Auk, from the book 'Birds of America' by John James Audubon.
Drawing depicting the Great Auk, from the book 'Birds of America' by John James Audubon.
John James Audubon, Wikimedia Commons // Public Domain

The tale of the dodo is one of the most famous stories of extinction in all natural history. Native only to the tiny island of Mauritius in the Indian Ocean, the birds had never learned any reason to be fearful of humans, so when European explorers first began to visit the island in the 17th century, the dodos were apparently so unsuspecting they could be picked up by hand straight from the wild and killed. Although the dodo was never a particularly numerous species (the fact that it was flightless made it susceptible to floods and forest fires, which apparently kept its population naturally low), within less than a century of its discovery, interference by humans had led to its extinction. But it's by no means alone—the stories behind the disappearance of 10 other creatures are listed here.

1. ATLAS BEAR

A Roman mosaic of the extinct Atlas bear.
A Roman mosaic of the extinct Atlas bear.
The Picture Art Collection / Alamy Stock Photo

The Atlas bear was the only species of bear native to Africa, and once inhabited the area around the Atlas Mountains in the far northwest of the continent. The bear's lengthy demise can be traced all the way back to the time of the Roman Empire, when the animals were not only hunted for sport but captured, brought back to Rome, and made to battle gladiators and execute criminals in a gruesome spectacle known as damnatio ad bestias. Numbers continued to fall throughout the Middle Ages, when great swaths of forest in northern Africa were felled for timber, until finally the last surviving wild Atlas bear was shot and killed in the mid-1800s.

2. CAROLINA PARAKEET

A mounted Carolina parakeet
James St. John, Wikimedia Commons // CC BY 2.0

The Carolina parakeet was once the only species of parrot native to the United States, found across a vast expanse of the country from New York in the north to the Gulf of Mexico in the south and the Rocky Mountains in the west. Excessive hunting and trapping meant that the birds had already become rare by the 19th century, but large, isolated flocks were still being recorded until as recently as the early 1900s. Sadly the birds were known for their altruistic habit of flocking to attend to dead or dying members of the same flock—so if only a few birds were felled by hunters, many of the rest of the flock would remain nearby, making themselves easy targets. The last known specimen died in the Cincinnati Zoo in 1918, and the species was finally declared extinct in 1939.

3. DUSKY SEASIDE SPARROW

A Dusky Seaside Sparrow outside on a branch
U.S. Fish and Wildlife Service, Wikimedia Commons // Public Domain

In 1963, a decision was made by NASA to flood a vast area of marshland on Merritt Island in eastern Florida as a means of controlling the mosquito population around the Kennedy Space Center. Sadly, Merritt Island was also one of the last strongholds of the dusky seaside sparrow, a small dark-colored songbird, and when the land was flooded, so too was the sparrows’ main breeding ground. Drainage of the marshes around the St. Johns River for a highway project also contributed to habitat loss. The birds' population collapsed, and in the years that followed, the species struggled to regain its numbers. By 1979, only five birds—all males—remained in the wild, and the sparrow was finally declared extinct in 1990.

4. GRAVENCHE

A drawing of a gravenche, an extinct freshwater fish
Wikimedia Commons // Public Domain

The gravenche was a species of freshwater fish native only to Lake Geneva, one of the Alpine lakes that straddle the border between France and Switzerland. The fish were apparently once so common in the lake that it alone accounted for two-thirds of all of the fish caught in Lake Geneva. Due to overfishing, the population of gravenche (Coregonus hiemalis) began to decrease rapidly in the early 20th century; the last known sighting was in 1950, and the species is now considered extinct.

5. GREAT AUK

Study of a great auk, circa 1910.
Hulton Archive, Getty Images

The penguin-like great auk was a large, flightless seabird once native to the entire North Atlantic Ocean, from Greenland and eastern Canada to the British Isles and the westernmost coasts of Europe. The birds were highly prized for their light and fluffy down, which was used as a stuffing for pillows and mattresses. And like the dodo, the fact that the birds were flightless made hunting and capturing them easy. The European population was almost entirely eradicated by the late 1600s, leading to one of the earliest environmental protection laws in history, passed by the British Parliament in 1770s, that prohibited killing the auks in Great Britain. Sadly, it was too late. As the birds became scarcer, demand for their feathers, meat and pelts increased, and the last two breeding birds were unceremoniously strangled to death on their nest by a pair of Icelandic hunters in 1844, while a third man stamped on the single egg that the female had been incubating.

6. HEATH HEN

Three Heath Hens
Game Birds, Wild-Fowl and Shore Birds of Massachusetts and Adjacent States, Massachusetts State Board Agriculture, Wikimedia Commons // Public Domain

Like the great auk, the North American heath hen was also the subject of an early protective bill, introduced to New York State legislature in 1791, but it too failed to save the species from extinction. Heath hens were once native to much of the northeast United States, and were so plentiful that their meat eventually gained a reputation for being "poor man's food." Nonetheless they continued to be hunted in such vast numbers that by the mid-1800s there were no hens at all left on the entire American mainland. The bird's final stronghold was Martha's Vineyard, Massachusetts, but illegal poaching, diseases carried by domestic poultry, and predation from feral cats caused numbers on the island to fall to less than 100 by the mid-1890s. A hunting ban and a specialized Heath Hen Reserve was introduced in 1908, and in response the population swelled to over 2000 in the years that followed. But a fire during the 1916 breeding season undid all of the reserve's hard work, and by 1927 there were only 12 birds—including just two females—left alive. The last lone male, nicknamed "Booming Ben" by the locals, died in 1932.

7. JAPANESE SEA LION

The 8-foot-long Japanese sea lion—an even larger cousin of the Californian sea lion—was once native to the Sea of Japan and bred in vast numbers along the beaches of the Japanese islands and the Korean mainland. Sadly, the animals were hunted in enormous numbers, but not for the reason you might think: their meat was poor quality and bad-tasting, so they weren't hunted for food, but rather for their skins (which were used to make leather), their bones (which were used in traditional medicines), their fat (which was rendered to make oil for oil lamps), and even their whiskers (which were used to make brushes and pipe cleaners). As recently as the early 1900s, more than 3000 sea lions were being killed every year in Japan, until the population collapsed to less than 50 individuals in 1915. Numbers remained low until the 1940s, when the maritime battles of the Second World War destroyed the last remaining colonies and much of their natural habitat. The last recorded (but unconfirmed) sighting was in 1974.

8. PASSENGER PIGEON

A stuffed passenger pigeon up for auction.
Rob Stothard, Getty Images

Until as recently as the early 1800s, the passenger pigeon was still considered the most numerous bird in all of North America. Individual flocks could contain in excess of a billion individual birds, and would take more than an hour to fly overhead. But as a hugely plentiful source of cheap meat, the birds were hunted in unprecedented numbers: at one nesting site in Michigan in 1878, as many as 50,000 birds were killed every day for nearly five months, and the last surviving flock of 250,000 birds was killed in its entirety by one group of hunters in a single day in 1896. The final individual bird—a female named Martha, who was being held in captivity at the Cincinnati Zoo—died in 1914.

9. STEPHENS ISLAND WREN

Wikimedia Commons // Public Domain

Stephens Island is a tiny half-mile islet lying in the seas between the two main islands of New Zealand. After a lighthouse was built there in 1892, the local lighthouse keeper's cat, Tibbles, caught a bird that the keeper didn't recognize. He sent the specimen to a renowned New Zealand ornithologist named Walter Buller, and the bird was soon declared a new species—the Stephens Island wren—and identified as one of only a handful of flightless perching birds known to science. Sadly, within just three years of its discovery, the species was extinct. According to popular history, Tibbles the cat was singlehandedly responsible for killing off the entire population of the wrens (in which case, Tibbles would be the only individual creature in history responsible for the extinction of an entire species) but in reality, by the late 1890s, Stephens Island was so overrun with feral cats that it is impossible to say that Tibbles alone was responsible: In February 1895, the lighthouse keeper wrote in a letter that "the cats have become wild and are making sad havoc among all the birds."

10. WARRAH

The warrah, or Falkland Island wolf or fox
Wikimedia Commons // Public Domain

The warrah, or Falkland Islands wolf, was a unique species of wolf that was once the only mammal species native to the Falkland Islands in the South Atlantic Ocean. It's thought that the species became trapped on the islands during the last Ice Age, when the Falklands were connected to the South American mainland by an ice bridge that left the animals isolated when it melted. After the Falkland Islands were first settled by humans in the 1760s, the wolves were seen as a threat to livestock and were quickly hunted into extinction. The warrah was already rare by the time Charles Darwin visited the Falklands in 1833, and he ominously predicted that, "within a very few years … this fox will be classed with the dodo as an animal which has perished from the face of the earth." Like the dodo, the warrah had never had to learn to be fearful of humans, and with no trees or forests on the island in which to hide, the wolves proved easy targets. The last individual was killed in 1876.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios