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6 Prehistoric Body Parts You Don’t See Anymore

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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

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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
What's the Difference Between Gophers and Groundhogs?
Gopher or groundhog? (If you chose gopher, you're correct.)
Gopher or groundhog? (If you chose gopher, you're correct.)
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Gophers and groundhogs. Groundhogs and gophers. They're both deceptively cuddly woodland rodents that scurry through underground tunnels and chow down on plants. But whether you're a nature nerd, a Golden Gophers football fan, or planning a pre-spring trip to Punxsutawney, Pennsylvania, you might want to know the difference between groundhogs and gophers.

Despite their similar appearances and burrowing habits, groundhogs and gophers don't have a whole lot in common—they don't even belong to the same family. For example, gophers belong to the family Geomyidae, a group that includes pocket gophers (sometimes referred to as "true" gophers), kangaroo rats, and pocket mice.

Groundhogs, meanwhile, are members of the Sciuridae (meaning shadow-tail) family and belong to the genus Marmota. Marmots are diurnal ground squirrels, Daniel Blumstein, a UCLA biologist and marmot expert, tells Mental Floss. "There are 15 species of marmot, and groundhogs are one of them," he explains.

Science aside, there are plenty of other visible differences between the two animals. Gophers, for example, have hairless tails, protruding yellow or brownish teeth, and fur-lined cheek pockets for storing food—all traits that make them different from groundhogs. The feet of gophers are often pink, while groundhogs have brown or black feet. And while the tiny gopher tends to weigh around two or so pounds, groundhogs can grow to around 13 pounds.

While both types of rodent eat mostly vegetation, gophers prefer roots and tubers (much to the dismay of gardeners trying to plant new specimens), while groundhogs like vegetation and fruits. This means that the former animals rarely emerge from their burrows, while the latter are more commonly seen out and about.

Groundhogs "have burrows underground they use for safety, and they hibernate in their burrows," Blumstein says. "They're active during the day above ground, eating a variety of plants and running back to their burrows to safety. If it's too hot, they'll go back into their burrow. If the weather gets crappy, they'll go back into their burrow during the day as well."

But that doesn't necessarily mean that gophers are the more reclusive of the two, as groundhogs famously hibernate during the winter. Gophers, on the other hand, remain active—and wreck lawns—year-round.

"What's really interesting is if you go to a place where there's gophers, in the spring, what you'll see are what is called eskers," or winding mounds of soil, Blumstein says [PDF]. "Basically, they dig all winter long through the earth, but then they tunnel through snow, and they leave dirt in these snow tunnels."

If all this rodent talk has you now thinking about woodchucks and other woodland creatures, know that groundhogs have plenty of nicknames, including "whistle-pig" and "woodchuck," while the only nicknames for gophers appear to be bitter monikers coined by Wisconsin Badgers fans.

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
Watch Christmas Island’s Annual Crab Migration on Google Street View
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Google

Every year, the 45 million or so red crabs on the remote Australian territory of Christmas Island migrate en masse from their forest burrows down to the ocean to mate, and so the female crabs can release their eggs into the sea to hatch. The migration starts during the fall, and the number of crabs on the beach often peaks in December. This year, you don’t have to be on Christmas Island to witness the spectacular crustacean event, as New Atlas reports. You can see it on Google Street View.

Watching the sheer density of crabs scuttling across roads, boardwalks, and beaches is a rare visual treat. According to the Google blog, this year’s crabtacular finale is forecasted for December 16, and Parks Australia crab expert Alasdair Grigg will be there with the Street View Trekker to capture it. That is likely to be the day when crab populations on the beaches will be at their peak, giving you the best view of the action.

Crabs scuttle across the forest floor while a man with a Google Street View Trekker walks behind them.
Google

Google Street View is already a repository for a number of armchair travel experiences. You can digitally explore remote locations in Antarctica, recreations of ancient cities, and even the International Space Station. You can essentially see the whole world without ever logging off your computer.

Sadly, because Street View isn’t live, you won’t be able to see the migration as it happens. The image collection won’t be available until sometime in early 2018. But it’ll be worth the wait, we promise. For a sneak preview, watch Parks Australia’s video of the 2012 event here.

[h/t New Atlas]

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