Wikimedia Commons
Wikimedia Commons

6 Prehistoric Body Parts You Don’t See Anymore

Wikimedia Commons
Wikimedia Commons

Sometimes the sheer wonder of the natural world can be overwhelming. So, at the risk of oversimplifying the following crazy-cool animals, allow us to highlight their most unusual structural features. You may find yourself wondering why these body parts haven’t been around in many, many millenia.

1. Anvil Fin - Stethacanthus

In most ways, Stethacanthus (above) probably looked like any of your average early sharks. Except, that is, for its bizarre anvil-shaped dorsal fin (sometimes described as an “ironing board”). Equally nonsensical is the rough patch of sharp, tooth-shaped scales atop the anvil/ironing board, and a second scaly patch on the top of its head which, like the anvil, seems pretty un-hydrodynamic.

At five to six feet long, Stethacanthus was among the smaller prehistoric sharks, and scientists have theorized that the weird dorsal shape might have served to mimic a huge mouth to deter would-be predators or competitors. But Stethacanthus wasn’t a very dynamic hunter, and probably stayed in shallower, coastal waters, feeding on small fish and crustaceans. More likely, the fin, the scales, and a pair of long, thin “whips” trailing from its sides have something to do with mating displays, as they’re only found on males of the genus.

2. Circular “Saw” Jaw - Helicoprion

Ray Troll

Helicoprion, a giant, shark-like “ratfish,” was host to one of the most notoriously baffling body parts ever discovered: a circular set of teeth that scientists now believe resembled a buzzsaw upended in the fish’s lower jaw. Back in 1899, scientist Alexander Karpinsky was left guessing after he discovered Helicoprion’s whirlygig of teeth sans the rest of the fish. For years, scientists and enthusiastic illustrators traded guesses as to how the teeth fit into an entire animal, which would prove to have reached lengths of 25 feet. They knew Helicoprion replaced its teeth intermittently, much like modern sharks, but it didn’t seem to share other sharky characteristics. The specifics of Helicoprion’s tooth replacement evaded them until earlier this year, when a team of Idaho State paleontologists pinned down the (still totally weird) mouth-mechanism seen here.

3. Tail Club - Ankylosaur

Wikimedia Commons

Most dino-inclined kids are well aware of the concept of the “tail club”: a tail which ends in a massive knob of bone and ossified tissue, good for defending against attackers, competing for mates, and knocking around whatever needs knocking around. Paleobiologist Victoria Arbour recently utilized CT scans to digitally reconstruct the muscles of the Ankylosaur’s tail club, allowing her to estimate the force with which the tail could smash. Her conclusions: Tail clubs with large “knobs” could break bone. Smaller-knobbed tail clubs, though, could do some lesser damage, leaving open the question as to whether tail clubs were more for offense, defense, or show. You know Ankylosaurs and their knob comparing.

4. “Baleen” Teeth - Pterodaustro

Wikimedia Commons

And speaking of size, Pterodaustro had the longest rostrum (snout) of any pterosaur, but its bottom teeth were truly the weirdest. Set in scooping underbite, its teeth were so long and skinny that they were all rooted a single, long groove in the bottom jaw instead of individual sockets. The overall effect is reminiscent of the baleen in modern whales, leading paleontologists to believe that Pterodaustro fed much in the same way, scooping up mouthfuls of muck from the shallows and filtering away the water to munch on what was left.

In modern whales, baleen is made out of keratin and is therefore more like hair than teeth, and for some time, scientists believed Pterodaustro’s teeth were composed of a similar protein. But closer inspection revealed microscopic evidence of real, toothy characteristics: enamel, dentine, and pulp cavities.

Here’s an hilarious and slightly outdated illustration of Pterodaustro in a synth rock video, for some reason.

5.  The Ol’ Single Claw - Mononykus

Wikimedia Commons

Named for the Latin Mono-, meaning “one,” and nykus, meaning “nail or claw,” Mononykus olecranus is a dinosaur best known for having only one claw on each of its puny forelimbs. And you thought T. rex had it bad.

Scientists have entertained many competing theories over the years as to the behavior of Mononykus olecranus, whose forelimbs would have been fairly useless for hunting or even grazing. The supposed presence of a birdlike chest ridge had many scientists believing M. olecranus may have been a winged but flightless bird. But a 2005 study examining range of motion in those stubby forearms decisively concluded that M. olecranus would have used its claws to scratch into insect nests and scoop out food. In this way, Mononykus’ single claw is analogous to modern animals with similar diets like anteaters and pangolins, though their claw count isn’t quite so minimalist.

6. Shoulder Spikes - Gigantspinosaurus

Wikimedia Commons

With one of the most satisfying names in taxonomy, this dino is named after the gigantic spikes that were situated on his shoulders. Exactly how they were situated on those shoulders (and therefore their exact purpose) is yet unknown, though it’s reasonable to guess that they were used for displaying and/or competing for mates. And before you ask, Gigantspinosaurus is indeed a stegosaur, just one of several members of the genus Stegosaurus. Another of Gigantspinosaurus’ close relatives, Kentrosaurus, may have had similar spikes on its shoulders, or possibly on its hips (on this spike-placement question, the jurassic jury’s still out). But Gigantspinosaurus appropriately maintains the record of largest shoulder spikes in prehistory.

A very special thanks to our good friend, prehistorian Brian Switek, for lending his expert eye to this piece!

NOAA, Wikimedia Commons // Public Domain
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

Joe Raedle, Getty Images
10 Things You Might Not Know About Grizzly Bears
Joe Raedle, Getty Images
Joe Raedle, Getty Images

Ursus arctos horribilis is better known by the more casual term of grizzly bear. These massive, brown-haired predators have a reputation as one of nature’s most formidable killing machines. Standing up to 8 feet tall and weighing 800 pounds, these fierce mammals have captivated—and frightened—humans for centuries. Keep your distance and read up on these facts about their love for munching moths, eating smaller bears, and being polar-curious.


Grizzlies—more accurately, North American brown bears—are strong enough to make a meal out of whatever they like, including moose, elk, and bison. Despite their reputation for having carnivorous appetites, their diet also consists of nuts, berries, fruits, and leaves. They’ll even eat mice. The gluttony doesn’t kick in until they begin to exhibit hyperphagia, preparing for winter hibernation by chomping down enough food to gain up to three pounds a day.


A grizzly bear eats fruit in Madrid, Spain
Dani Pozo, AFP/Getty Images

More than 700 grizzlies live in or near Yellowstone National Park, which forces officials to constantly monitor how park visitors and the bears can peacefully co-exist. Because bears rummaging in food containers can lead to unwanted encounters, the park’s Grizzly & Wolf Discovery Center tests trash cans and coolers to see if they’re bear-resistant. (Nothing is truly bear-proof.) Often, a bear will use “CPR,” or jumping on a canister with its front legs, in order to make the lid pop off. Containers that can last at least 60 minutes before being opened can be advertised by their manufacturers as being appropriate for bear-inhabited environments.


It's a myth that grizzlies can't climb trees. Though their weight and long claws make climbing difficult [PDF], and they need support from evenly-spaced branches, grizzlies can travel vertically if they choose to.


Two grizzly bears play in a pool at a zoo in France
Jean-Francois Monier, AFP/Getty Images

In addition to being omnivorous, grizzlies can also be classified as cannibals. They’ve been spotted eating the carcasses of black bears in Canada. Calling it a “bear-eat-bear world,” officials at Banff National Park in Alberta said the grizzlies are “opportunistic” and more than willing to devour black bears—sometimes just one-fifth their size—if the occasion calls for it. And it’s not just black bears: One study on bear eating habits published in 2017 recorded a 10-year-old male eating a 6-year-old female brown bear.


Although grizzlies enjoy eating many insects, moths are at the top of the menu. Researchers have observed that bears are willing to climb to alpine heights at Montana’s Glacier National Park in order to feast on the flying appetizers. Grizzlies will turn over rocks and spend up to 14 hours in a day devouring in excess of 40,000 moths.


A grizzly bear appears at the Wild Animal Sanctuary in Keenseburg, Colorado
John Moore, Getty Images

In what would be considered an ill-advised decision, explorer Zebulon Pike decided to gift his friend President Thomas Jefferson with two grizzly cubs in 1807. Jefferson reluctantly accepted them and kept them in a cage near the north entrance to the White House, and later re-gifted the cubs to museum operator Charles Willson Peale. Sadly, one of them got shot after getting too aggressive with Peale’s family.


The bears we see in fiction or lazing about in the wild tend to look cumbersome and slow, as most anything weighing nearly a half-ton would. But in a land race, even Olympic champions would be on the losing end. Grizzlies can reportedly run 35 mph, and sustain speeds of up to 28 mph for two miles, faster than Usain Bolt’s 27.78 miles per hour stride (which he can only sustain for a few seconds).


A grizzly bear is shown swimming at a pool in an Illinois zoo
Scott Olson, Getty Images

In parts of Alaska and Canada where grizzlies and polar bears converge, there are sometimes rare sightings of what observers call “grolar bears” or “pizzlies.” With large heads and light-colored fur, they’re a hybrid superbear birthed from some interspecies mating. Typically, it’s male grizzlies who roam into those territories, finding female polar bears to cozy up with. Researchers believe climate change is one reason the two are getting together.


When it comes to intellect, grizzlies may not get all the same publicity that birds and whales do, but they’re still pretty clever. The bears can remember hotspots for food even if it’s been 10 years since they last visited the area; some have been observed covering tracks or obscuring themselves with rocks and trees to avoid detection by hunters.


A grizzly bear and her cub walk in Yellowstone National Park
Karen Bleier, AFP/Getty Images

For 42 years, grizzlies at Yellowstone occupied the endangered species list. That ended in 2017, when the U.S. Fish and Wildlife Service declared that a rise in numbers—from 150 in the 1970s to more than 700 today—meant that conservation efforts had been successful. But overall, the grizzly population is still struggling: Fewer than 2000 remain in the lower 48 states, down from 50,000 two centuries ago.


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