A good number of scientists took one passing look at those chompers and assumed that they were ideal for grinding flesh and crushing bone, and nothing else. With no other evidence to go on, early paleontologists straight up panicked and let their imaginations run amok. This resulted in increasingly hyperbolic claims, like that mastodons had claws and the agility of a tiger and ruled the American continents with unparalleled ferocity. According to one anonymous author:

"Forests were laid waste at a meal, the groans of expiring animals were everywhere heard; and whole villages, inhabited by men, were destroyed in a moment."

It's amazing that guy knew these things hated humanity just by looking at a bone! Sounds like somebody has a bright future writing for Cracked.

Union County Parks Dept.
Especially if he just assumed this was a mastodon's fossilized terror dong.

Colonial Americans had an ulterior motive for believing in the flesh-eating mastodon. Unlike the wild continents of Africa and Asia, North America didn't really have any impressively dangerous animals like lions or rhinos. It soon became kind of a joke for the rest of the naturalist world. So the discovery of the mastodon became a source of nationalist pride for the early United States -- a monster so vicious and ferocious that even the rules of basic biology couldn't contain its bloodlust. Thomas Jefferson even assigned Lewis and Clark a secondary mission objective: to find evidence of living mastodons pillaging native villages in the wild uncharted West.

In the meantime, a mastodon skeleton featured in the Philadelphia Museum was altered to look tougher, with its tusks turned downward like a saber-toothed tiger:

Edouard de Montulé, via Common-Place.org

Meanwhile, other researchers came up with even more creative theories:

Alexander Anderson, via Common-Place.org
"What big eyes you have."
"THE BETTER TO STAB YOU WITH."

Of course, today's scientists have a better theory about why the mastodon's teeth look like something out of a grinding mill -- they were for grinding. Grinding up branches and tough vegetable matter. As for the elusive claws, they never found any evidence for that either, but hopefully that won't stop them from making a SyFy original movie out of it.

That shingled-roof formation is actually what gave the stegosaurus its name, and all things considered, it was a fairly reasonable assumption to make. Hell, we have tiny versions of that animal around now. It wasn't until years later that scientists started standing the plates upright, eventually shuffling them around to the version we recognize today.

But if the plates weren't armor, it raised a whole new question: What exactly did these plates do? Were they used for protection? Temperature control? Could they fold those suckers down like wings and take off like an airplane? Haha, that would be ridic-

Ogden Standard-Examiner
"Dude, you forgot to add the totally bitchin' flames decals. I need this to be accurate."

Citing just a little less than zero scientific research to back up his claim, one "Dr. W. H. Ballou" wrote an article in the Ogden Standard-Examiner describing how stegosaurus plates could fold down at will, creating "gliding surfaces immeasurably like those of the planes of to-day." That's right: All it took for a 5-ton behemoth to leap from a cliff and sail gracefully across the Jurassic skies were a series of miniscule back-plates and giant dinosaur balls. To push this madness even further, Ballou asserted that the stegosaurus was a direct ancestor of modern birds (it wasn't, of course) and its plates were actually where wings came from.

As brain-clubbingly stupid as the idea was, it did find some purchase in pop culture. Ballou's Flying Stego-Circus appears to have inspired a scene in Edgar Rice Burroughs' Tarzan at the Earth's Core, where a gliding stegosaurus swoops down from the cliffs to terrorize an explorer, who proceeds to leap off the mountainside with a pair of six-guns and blow the hell out of its tiny brain in a free-falling battle of the ages.

Holy shit! Sounds like we all have some reading to do.

This all started when we discovered that the stegosaurus and the big sauropods had swollen spinal cavities near the hips -- even larger than the space inside the cranium. So scientists theorized that these cavities were a braincase for a second, auxiliary brain. This "sacral brain" supposedly gave them the intelligence boost they needed to control the back half of their bodies, which is kind of like suggesting that putting a second steering wheel in the cargo hold of an 18-wheeler would make it drive better. Growing a whole separate brain just to shake what evolution gave ya isn't common practice in nature. A more sensible reason for these dinosaurs' enlarged ass cavities could be found by looking at birds: Birds have the same kind of spinal swelling, which stores up nutrient-rich deposits, and nowadays scientists think that these big-booty dinosaurs might've had the same junk in their trunks. Or maybe they used it to store weed in case they got pulled over, who knows -- it's just probably not a second brain.

Fernbank Museum
Although we have to admit, it'd be nice to appear deep in thought while scratching your ass.

The trouble is, dinosaur books kept teaching the butt-brain hypothesis as a fact for so long that it became firmly lodged all the way up the public's imagination. The myth still pops up from time to time, too ... like in Pacific Rim, where one scientist casually quips that the giant kaiju need two brains to walk around, "like a dinosaur." Not that anyone holds up Pacific Rim as a pillar of scientific authority -- the movie gets a pass for being generally awesome and never giving the slightest shit about realism in the first place.

But how about Discovery Channel specials? In the series Clash of the Dinosaurs, guest paleontologist Matt Wedel discussed the evidence against the two-brain hypothesis in a filmed interview, but since double-brained dinosaurs make for more fascinating TV, the editors deliberately chopped his words until he endorsed the idea. Only after he issued a bitter complaint did Discovery try to set his words straight ... long after the myth was spread to thousands of viewers. What a bunch of butt-brains.

The defining feature of the dimetrodon is its sail:

Charles R. Knight, via Wikimedia
Along with its propensity to look hilarious during heavy winds.

But this wasn't always the case. Back in the early days of paleontology, when scientists were digging up these skeletons, dressing them in funny hats, and performing vaudeville routines, all that remained of dimetrodon's sails after millions of years were rows of bony spikes. That's why the first re-creations of this dinosaur looked more like a walking mohawk:

H.F. Cleland, via Brian Switek
Seen here in one of the few illustrations that didn't feature a safety pin nose piercing.

Back in 1911, German paleontologist Otto Jaekel proposed that dimetrodon's protruding back spikes were a defensive weapon against predators -- sort of a giant, reptilian hedgehog. Which is, of course, totally awesome, and we could see why he said it. Then he got a bit carried away making up awesome crap about thunder-lizards and went on to posit that dimetrodon could twist its spine around like a corkscrew, pointing its spikes in all directions like a hellish Tinkertoy wheel.

Dimetrodon also had a vegetarian cousin, edaphosaurus, who was given the same sail-less treatment on the wall of the Berlin Aquarium. The bones of edaphosaurus had little branches sticking out of them, which our old friend Edward Drinker Cope thought might've helped the animal blend in with the undergrowth of a wooded environment.

Berlin Aquarium, via Dinosaurpalaeo
Yep. Totally blending in. Where is the giant friggin' dinosaur in this picture?!

Failing that, Cope had an alternate explanation: Instead of having one big sail, each of edaphosaurus' sailbones supported an individual sail, like the masts on a ship, and these sails could be turned to the wind for the animal to navigate the surface of prehistoric lakes. That's right, the sail of edaphosaurus was thought to be used for actual sailing. Just a big ol' vicious lizard, using his belly as a boat and yachting about with his backfins.

Remember: Both cocaine and heroin used to be totally legal back in the day.

Hey, remember when scientists discovered that T. rex probably had feathers? Oh, you actually physically can't forget, because we've pounded that information into your brain so many times that it's replaced your own phone number? Sorry about that. But yeah, it turns out this rabbit hole goes a lot deeper.

Isn't it strange that dinosaurs all look pretty much exactly like their skeletons with a bit of meat stretched over them? You know that's not how living animals work. We've shown you the terror lurking beneath the skin already. The phenomenon of dinosaurs closely resembling their skeletons is known as shrink-wrapped dinosaur syndrome, and if we drew today's animals by the same standards, we'd end up with baboons straight from the concept art for Resident Evil:

C.M. Kosemen

Or how about a beautiful swan, transformed into a terrifying predator that spears fish with its scythe-like arms:

C.M. Kosemen
In fairness, the updated swan paddle boats are pretty kickass.

In reality, the truth about what dinosaurs really looked like is open to as much speculation as your imagination will allow. There's really no way of knowing if dinosaurs had feathers, or turkey crests, or even trunks.

Bill Munns
This is a real idea that scientists have argued about.

In light of this, some authors have put together a book speculating about what might actually pop out if we ever manage to clone dinosaurs like in Jurassic Park:

John Conway

Emiliano Troco

John Conway
At least the feathered T. rex can feel a little less ridiculous.

Nobody's saying the above representations are accurate -- it's pure guesswork. But hard evidence for this sort of thing is cropping up already: A recent discovery of a duck-billed edmontosaurus in Canada came preserved with a flappy rooster's comb on top of its head. It's precisely the sort of bizarre crap that you find on modern animals all the time:

Julius Csotonyi / Current Biology
"The crest is almost stupid-looking enough, but could we draw his snout to look like ridiculous buck teeth, too?"

So basically we're saying that all those terrifying, lean, sleek killing machines from Jurassic Park may have never existed, at least not in the way you think of them. In reality, they could have been a bunch of waddle-having, flappy-skinned, feathered, bright purple goofballs.

We're sorry.

Mr. Yee sticks random bones together to create the Internet's largest comedy fortune cookie and some fairly amusing T-shirts.

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Related Reading: If you think Hunter-Gatherers lived lives of miserable starvation, than you're even more wrong than all those paleontologists. For the hilariously stupid versions of our modern animals, you'd be best served by clicking here. And if you'd rather look at some ancient animals that will give you waking nightmares, this article can oblige. Say hello to the Murderbird with a 40-foot wingspan for us!