11 Fishy Facts About Coelacanths

There are plenty of fish in the sea, but few are more astounding than the coelacanths—a group that defied extinction and turned the scientific world upside down.


During the Devonian, which lasted from 416 to 358 million years ago, ferns evolved, trilobites still roamed the oceans, vertebrates took their first steps onto dry land, and fish began to diversify—hence the period's nickname, "the age of fish." The oldest-known coelacanth appeared in present-day Australia during this time, between 407 and 409 million years ago. Like modern coelacanths, the creature belonged to a group known as the sarcopterygians, or “fleshy-limbed vertebrates.” These animals are defined by their bony skeletons and fleshy, muscular fins that bear a striking resemblance to our own limbs. The similarity is no coincidence: By the end of the Devonian, the sarcopterygians would give rise to the first terrestrial vertebrates, which, in turn, begat the amphibians, the reptiles, and—eventually—mammals like us. Indeed, to modern biologists, humans aren’t descended from sarcopterygians, we actually are sarcopterygians.


It’s a reference to the hollow, rod-like rays that are present in the creatures’ dorsal fins. The term coelacanth is descended from Coelacanthus granulatus, a name that zoologist Louis Agassiz gave to a prehistoric British species in the 1830s. As it happens, Coelacanthus granulatus was the first coelacanth to ever be scientifically described. Since then, over 120 additional species have been found—including those that are still alive today. (More about them later.)


After the Devonian, coelacanths flourished, evolving to fill an array of different niches. Many were slow-moving marine carnivores that must have ambushed passing prey items, but at least one fossil coelacanth was an active, speedy predator. Discovered in 2012, Rebellatrix divaricerca terrorized the seas that covered British Columbia around 250 million years ago. A sleek creature with a forked tail, the fish probably chased down smaller animals over great distances. Another notable species was Megalocoelacanthus, a toothless giant that grew to be 10 feet long. A few coelacanths left the ocean altogether and became freshwater denizens [PDF]. Some of these lake and river fish would have no doubt encountered the occasional dinosaur.


Coelacanths past and present constitute an entire order of fish—and for a century, paleontologists believed that the whole lot was wiped out in the same extinction that claimed the dinosaurs (birds notwithstanding) some 66 million years ago. But then, just a few days before Christmas in 1938, a trawler on the Indian Ocean caught a strange-looking fish in its nets. That vessel, the Nerine, was captained by Hendrik Goosen, though he took no notice of the odd beast he’d reeled in. The Nerine proceeded as usual to its destination: a fish market in East London, South Africa. Upon docking there, Goosen—as was his custom—called Marjorie Courtenay-Latimer.

Courtenay-Latimer, the curator of a local museum, had befriended the captain, who would always invite her to comb through his latest haul for odd-looking specimens. But on that day in 1938, she nearly turned him down—she had her hands full with a new fossil exhibit. In the end, Courtenay-Latimer decided to drop by anyway, if only to wish the crew a Merry Christmas.

She would later recount that "I picked away the layers of slime to reveal the most beautiful fish I had ever seen. It was 5 feet long, a pale, mauvy blue with faint flecks of whitish spots; it had an iridescent silver-blue-green sheen all over. It was covered in hard scales, and it had four limb-like fins and a strange little puppy dog tail. It was such a beautiful fish—more like a big china ornament—but I didn't know what it was.” Courtenay-Latimer recovered the corpse, stuffed it, and contacted renowned chemist and ichthyologist J.L.B. Smith. Two months later, he confirmed that her mystery fish was, in fact, a modern-day coelacanth. To honor its discoverer, Smith named the creature Latimeria chalumnae.


Latimeria chalumnae is commonly referred to as the West Indian Ocean coelacanth. Capable of reaching over 6 feet in length, this metallic-blue carnivore occupies the waters off of South Africa, Madagascar, Mozambique, and the Comoro Islands. A deep-sea creature by nature, West Indian Ocean coelacanths typically live at depths of around 300-1000 feet, but have been found at 2000 feet beneath the waves. Their hunting sessions mainly occur at night—during the day, the fish retire to undersea caves, where they hang out in groups of up to 16 individuals.

A smaller, brown-colored species called the Indonesian coelacanth (Latimeria menadoensis) came to light during the late 1990s. Relatively little is known about this elusive creature and only a handful of specimens have ever been documented. At present, both Latimeria species may be in trouble. The West Indian Ocean coelacanth is considered critically endangered and its Indonesian relative has been classified as vulnerable by the International Union for Conservation of Nature (IUCN). If both animals should go extinct, the whole coelacanth order will die out with them—this time, for real.


Unlike any other animal that is presently alive, coelacanths have an intracranial joint behind the eyes that splits the skull in two, enabling the entire snout to swing upward when a coelacanth opens its mouth. The joint allows coelacanths to take disproportionately wide bites and, as biologist Hugo Dutel explains in this video, the joint and its corresponding muscles “[enhance] the overall bite force during the capture of prey.” Keep your fingers away from those teeth, folks.


CT scans have shown that the embryos of these fish start growing lungs at an early point in their lengthy gestation period. Over time, however, a coelacanth’s lung development slows, and by the time it becomes an adult, the organs cease to serve any discernible purpose. Also noteworthy is the fact that flexible plates surround the useless lungs in full-grown Latimeria. Some coelacanth fossils exhibit similar structures.


Fast-forward to 0:55 in the above video and you’ll observe a curious display. On many occasions, wild coelacanths have been seen adopting what’s often described as a “headstand position.” For up to two full minutes, the fish angle themselves downward, holding their snouts perpendicular to the ocean floor. The maneuver’s purpose is a mystery, although some experts think that it may help the animals track their prey.


Although the mechanics of coelacanth reproduction aren’t fully understood, we do know that their eggs are fertilized within the mother’s body. In 2013, a German team analyzed the corpses of two pregnant Latimeria chalumnae. DNA testing revealed that their unborn broods had each been sired by a single father. This revelation really caught the scientists off-guard.

“For both [of our specimens], it was clear that there was only one male involved,” Dr. Kathrin Lampert, a biologist who helped orchestrate the study, told New Scientist. Going into the tests, she and her colleagues fully expected to find that the eggs had been fertilized by many different males. After all, by breeding with several partners, a mother coelacanth could dramatically increase her clutch’s genetic diversity.

“Monogamous mating systems are most commonly found in species where the father provides parental care or where there is no opportunity for polygamy,” Lampert’s team noted in their report. Perhaps, they argue, female coelacanths save valuable energy by limiting themselves to just one mate per breeding season.


As a coelacanth gets older, its brain tissue grows at a much slower rate than the rest of its body. In a full-grown adult, the brain itself fills less than 1.5 percent of the brain cavity. The remainder of that space is occupied by fat. Juveniles, meanwhile, have proportionately larger thinking organs and less fat in their braincases.


On September 10, 1975, a dead coelacanth that had been sitting in an aquarium at the American Museum of Natural History since 1962 was dissected. The decision to cut it up had been made when a hematologist named Charles Rand of Long Island University expressed an interest in acquiring some spleen samples. Together, Dr. Rand, paleontologist Bobb Schaeffer, and ichthyologists James Atz and C. Lavett Smith took a scalpel to the fish.

A huge surprise lay in wait beneath its skin. Within this deceased sarcopterygian, the astonished scientists found five embryonic coelacanths. These unborn babies revealed that, unlike most fish, the magnificent Latimeria chalumnae gives birth to live young.

Elated by the breakthrough, Rand started waxing poetic—or should we say operatic? With a parodic zeal that would do "Weird Al" Yankovic proud, the musically-inclined hematologist wrote some lyrics for a new operetta titled A Coelacanth’s Lament, or Quintuplets at 50 Fathoms Can Be Fun. His rhymes were set to the melody of various Gilbert and Sullivan songs, including “Tit Willow” from their 1885 comedic masterpiece The Mikado. Fortunately for all of us, the AMNH has been good enough to upload a few of Rand’s verses. Enjoy.

20 Black-and-White Facts About Penguins

To celebrate World Penguin Day (which is today, April 25), here are a few fun facts about these adorable tuxedoed birds.

1. All 17 species of penguins are found exclusively in the Southern Hemisphere.

2. Emperor Penguins are the tallest species, standing nearly 4 feet tall. The smallest is the Little Blue Penguin, which is only about 16 inches.

emperor penguin

3. The fastest species is the Gentoo Penguin, which can reach swimming speeds up to 22 mph.

Gentoo Penguin

4. A penguin's striking coloring is a matter of camouflage; from above, its black back blends into the murky depths of the ocean. From below, its white belly is hidden against the bright surface.

penguins swimming in the ocean

5. Fossils place the earliest penguin relative at some 60 million years ago, meaning an ancestor of the birds we see today survived the mass extinction of the dinosaurs.

emperor penguins

6. Penguins ingest a lot of seawater while hunting for fish, but a special gland behind their eyes—the supraorbital gland—filters out the saltwater from their blood stream. Penguins excrete it through their beaks, or by sneezing.

penguins swimming in the ocean

7. Unlike most birds—which lose and replace a few feathers at a time—penguins molt all at once, spending two or three weeks land-bound as they undergo what is called the catastrophic molt.

molting penguin

8. All but two species of penguins breed in large colonies of up to a thousand birds.

king penguins

9. It varies by species, but many penguins will mate with the same member of the opposite sex season after season.

chinstrap penguins

10. Similarly, most species are also loyal to their exact nesting site, often returning to the same rookery in which they were born.

maegellic penguin nesting

11. Some species create nests for their eggs out of pebbles and loose feathers. Emperor Penguins are an exception: They incubate a single egg each breeding season on the top of their feet. Under a loose fold of skin is a featherless area with a concentration of blood vessels that keeps the egg warm.

penguin eggs

12. In some species, it is the male penguin which incubates the eggs while females leave to hunt for weeks at a time. Because of this, pudgy males—with enough fat storage to survive weeks without eating—are most desirable.

emperor penguins

13. Penguin parents—both male and female—care for their young for several months until the chicks are strong enough to hunt for food on their own.

Penguins nest

14. If a female Emperor Penguin's baby dies, she will often "kidnap" an unrelated chick.

penguin chicks

15. Despite their lack of visible ears, penguins have excellent hearing and rely on distinct calls to identify their mates when returning to the crowded breeding grounds.

16. The first published account of penguins comes from Antonio Pigafetta, who was aboard Ferdinand Magellan's first circumnavigation of the globe in 1520. They spotted the animals near what was probably Punta Tombo in Argentina. (He called them "strange geese.")

17. An earlier, anonymous diary entry from Vasco da Gama's 1497 voyage around the Cape of Good Hope makes mention of flightless birds as large as ducks.

18. Because they aren't used to danger from animals on solid ground, wild penguins exhibit no particular fear of human tourists.

19. Unlike most sea mammals—which rely on blubber to stay warm—penguins survive because their feathers trap a layer of warm air next to the skin that serves as insulation, especially when they start generating muscular heat by swimming around.

20. In the 16th century, the word penguin actually referred to great auks (scientific name: Pinguinus impennis), a now-extinct species that inhabited the seas around eastern Canada. When explorers traveled to the Southern Hemisphere, they saw black and white birds that resembled auks, and called them penguins.

6 Myths About Animals, Debunked

It’s easy to think we understand animals: They’re present in every part of our culture, from the movies we watch to the clichés we use. But the way a species functions in the wild is often worlds apart from a stereotype or cartoon. This gulf between misconceptions and reality is the theme of Lucy Cooke’s new book, The Truth About Animals.

"We have a habit of viewing the animal kingdom through the prism of our own existence, and that trips us up and obscures the truth,” Cooke, a zoologist and founder of the Sloth Appreciation Society, tells Mental Floss. “I think it's time we rebrand the animal kingdom according to facts and not sentimentality.”

As Cooke examines in her book, the real world is one in which pandas are virile lovers and sloths are master survivalists. These are just a few of the myths that were debunked in The Truth About Animals.


Pandas have long been blamed for their own precarious position in the animal kingdom. The species is in danger, some people claim, because pandas are reluctant to or just plain bad at copulating. If only they would get off their furry behinds and get it on, there would be more of them.

In The Truth About Animals, Cooke debunks this modern myth. Pandas have been living in the wild for 18 million years—long before humans swooped in to act as their savior—and that wouldn’t be the case without healthy sex habits. It’s true that pandas are difficult to breed in captivity, and the several failed attempts of zoos to produce a baby panda throughout the 20th century is likely what led to this stereotype. But the bears are much more responsive to members of the opposite sex in the wild. The female chooses who she mates with, moaning from high in a bamboo tree while several males on the ground compete for her attention. Once the bears have paired off, they can have sex over 40 times in one afternoon.


Cooke was inspired to write her book by sloths, which she describes to Mental Floss as “highly successful, highly evolved” creatures. Not everyone agrees: More than perhaps any other animal, sloths have become synonymous with laziness and sluggishness, and today they’re held up as an example of evolutionary failure.

The reality is that sloths are much more impressive than their appearance suggests. They’ve been around since 64 million years ago—earlier than wooly mammoths and saber-toothed tigers—and they have their slow and steady nature to thank for their success. Sloths have a remarkably slow digestive system and a low-calorie diet, so they expend as little energy as possible, not out of laziness, but out of survival instinct. A sloth is awake for more than half the day, and when necessary it can scramble up a tree at speeds approaching 1 mph. It spends most of its day in a still, seemingly trancelike state, but it isn’t wasting its potential: It’s conserving energy so it can maintain its dominant spot in the evolutionary tree.


Emperor penguins, the most famous of the bird group, are known for splitting parenting duties between mated pairs, with the father incubating the egg while the mother gathers food for her family. This has led some to praise penguins as the reflection of ideal, moral family dynamics in the animal kingdom, but these people should probably find a different analog. Though the parents of any given chick may raise their offspring together, penguins aren’t monogamous: 85 percent of emperor penguins find a new partner from one breeding season to the next. Penguins are also some of the only animals known to exchange goods for sex. Adélie penguins need rocks to build up their nests during warmer months when meltwater threatens their eggs. With no parenting duties to distract them, bachelor penguins end up collecting more stones than they need, so some females will sometimes trade a one-off sex session for one of their pebbles.


Watch enough survival movies and you’re bound to see a shot of a hungry vulture trailing behind the starving protagonist, waiting for them to lie down and die. The myth that vultures stalk their prey while it’s still alive and have the power to predict death is a persistent one, but that doesn’t make it accurate. The scavengers have no interest in living animals and will only seek out meat from dead and decaying corpses. Rather than reaper-like premonitions of mortality, turkey vultures and greater and lesser yellow-headed vultures use their noses to locate their meals. They join kiwis and kakapos on the small list of birds with highly-developed olfactory glands. Without a strong sense of smell, other New World vultures and all Old World vultures primarily rely on sight to find food. Some New World vultures like black vultures have adopted a different strategy: They'll follow turkey vultures to their prey, taking advantage of their sensitive noses.


Bats may be the animals most closely associated with the horror genre. They crave blood, so the myth goes, and though a bat latched onto your neck won’t be able to suck you dry, it will likely infect you with a nasty case of rabies.

According to Cooke, there are many problems with the statement above. Bats are poor stand-ins for their fictional vampire counterparts; only three species of bats drink blood—the common vampire bat, the hairy-legged vampire bat, and the white-winged vampire bat—while most prefer fruit or insects. After climbing onto its prey, the vampire bat locates where the blood is flowing with the heat sensor on its nose, and then, using its sharp front teeth like shears, it cuts away any hair that might be blocking the skin. Rather than biting down and sucking like Dracula, the bat creates a small incision and laps up blood from the open wound. They can recognize an individual animal's breathing patterns and return to feed on it the following night, taking advantage of the reliable blood source.

Bats are rarely rabid, with just .05 percent of them carrying the disease—less than dogs or raccoons. The image of a bat getting tangled in your hair also has no basis in reality: Their sophisticated echolocation system signals them to turn long before they have a chance to collide with your head.


Hyena genitalia has been baffling scientists for centuries. Member of both sexes appear to have a penis, while in females there’s no external vagina to be found. Scientists originally thought that hyenas must be hermaphrodites, but the true explanation is even more unusual. Though it’s often referred to as a pseudo-penis, female hyena genitalia doesn’t produce sperm, technically making it a nearly 8-inch-long clitoris. This appendage is also saddled with all the same duties as a conventional female organ, including giving birth to hyena pups.


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