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6 Prehistoric Body Parts You Don’t See Anymore

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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

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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

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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

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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

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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!

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Big Questions
Why Can't Dogs Eat Chocolate?
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Even if you don’t have a dog, you probably know that they can’t eat chocolate; it’s one of the most well-known toxic substances for canines (and felines, for that matter). But just what is it about chocolate that is so toxic to dogs? Why can't dogs eat chocolate when we eat it all the time without incident?

It comes down to theobromine, a chemical in chocolate that humans can metabolize easily, but dogs cannot. “They just can’t break it down as fast as humans and so therefore, when they consume it, it can cause illness,” Mike Topper, president of the American Veterinary Medical Association, tells Mental Floss.

The toxic effects of this slow metabolization can range from a mild upset stomach to seizures, heart failure, and even death. If your dog does eat chocolate, they may get thirsty, have diarrhea, and become hyperactive and shaky. If things get really bad, that hyperactivity could turn into seizures, and they could develop an arrhythmia and have a heart attack.

While cats are even more sensitive to theobromine, they’re less likely to eat chocolate in the first place. They’re much more picky eaters, and some research has found that they can’t taste sweetness. Dogs, on the other hand, are much more likely to sit at your feet with those big, mournful eyes begging for a taste of whatever you're eating, including chocolate. (They've also been known to just swipe it off the counter when you’re not looking.)

If your dog gets a hold of your favorite candy bar, it’s best to get them to the vet within two hours. The theobromine is metabolized slowly, “therefore, if we can get it out of the stomach there will be less there to metabolize,” Topper says. Your vet might be able to induce vomiting and give your dog activated charcoal to block the absorption of the theobromine. Intravenous fluids can also help flush it out of your dog’s system before it becomes lethal.

The toxicity varies based on what kind of chocolate it is (milk chocolate has a lower dose of theobromine than dark chocolate, and baking chocolate has an especially concentrated dose), the size of your dog, and whether or not the dog has preexisting health problems, like kidney or heart issues. While any dog is going to get sick, a small, old, or unhealthy dog won't be able to handle the toxic effects as well as a large, young, healthy dog could. “A Great Dane who eats two Hershey’s kisses may not have the same [reaction] that a miniature Chihuahua that eats four Hershey’s kisses has,” Topper explains. The former might only get diarrhea, while the latter probably needs veterinary attention.

Even if you have a big dog, you shouldn’t just play it by ear, though. PetMD has a handy calculator to see just what risk levels your dog faces if he or she eats chocolate, based on the dog’s size and the amount eaten. But if your dog has already ingested chocolate, petMD shouldn’t be your go-to source. Call your vet's office, where they are already familiar with your dog’s size, age, and condition. They can give you the best advice on how toxic the dose might be and how urgent the situation is.

So if your dog eats chocolate, you’re better off paying a few hundred dollars at the vet to make your dog puke than waiting until it’s too late.

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

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Animals
Elusive Butterfly Sighted in Scotland for the First Time in 133 Years

Conditions weren’t looking too promising for the white-letter hairstreak, an elusive butterfly that’s native to the UK. Threatened by habitat loss, the butterfly's numbers have dwindled by 96 percent since the 1970s, and the insect hasn’t even been spotted in Scotland since 1884. So you can imagine the surprise lepidopterists felt when a white-letter hairstreak was seen feeding in a field in Berwickshire, Scotland earlier in August, according to The Guardian.

A man named Iain Cowe noticed the butterfly and managed to capture it on camera. “It is not every day that something as special as this is found when out and about on a regular butterfly foray,” Cowe said in a statement provided by the UK's Butterfly Conservation. “It was a very ragged and worn individual found feeding on ragwort in the grassy edge of an arable field.”

The white-letter hairstreak is a small brown butterfly with a white “W”-shaped streak on the underside of its wings and a small orange spot on its hindwings. It’s not easily sighted, as it tends to spend most of its life feeding and breeding in treetops.

The butterfly’s preferred habitat is the elm tree, but an outbreak of Dutch elm disease—first noted the 1970s—forced the white-letter hairstreak to find new homes and food sources as millions of Britain's elm trees died. The threatened species has slowly spread north, and experts are now hopeful that Scotland could be a good home for the insect. (Dutch elm disease does exist in Scotland, but the nation also has a good amount of disease-resistant Wych elms.)

If a breeding colony is confirmed, the white-letter hairstreak will bump Scotland’s number of butterfly species that live and breed in the country up to 34. “We don’t have many butterfly species in Scotland so one more is very nice to have,” Paul Kirkland, director of Butterfly Conservation Scotland, said in a statement.

Prior to 1884, the only confirmed sighting of a white-letter hairstreak in Scotland was in 1859. However, the insect’s newfound presence in Scotland comes at a cost: The UK’s butterflies are moving north due to climate change, and the white-letter hairstreak’s arrival is “almost certainly due to the warming climate,” Kirkland said.

[h/t The Guardian]

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