Just to add insult to horror, it turns out that the hagfish doesn't even really need a mouth, considering that it can actually eat with its skin. It generally gets its nutrition from swimming around in putrid waters around decomposing corpses and absorbing the delicious corpse juices through its pores. It seems like the only reason it has four rows of yellow fangs is because God had to match a quota for horrible things.

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The leatherback sea turtle is one of those animals you can post on your friend's Facebook page to cheer them up after a shitty day. Because damn, look at the cute little guy.

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But if you're utilizing the leatherback turtle for its powers of adorableness, make sure that you don't take a picture of it while it's yawning, because oh God, Jesus no, it looks like the sarlaac.

Those hundreds of jagged stalactites that line the turtle's mouth and esophagus all the way down to its horrible, horrible gut are called papillae, and they exist because the universe hates beauty, and also because the leatherback turtle's diet consists entirely of jellyfish and other soft-bodied, slimy invertebrates. Anyone who's ever tried to catch a jellyfish with two spoons would give their left nut for a fork, which is why the turtle is equipped with its own murder cavern. Those jellyfish are going nowhere.

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Leatherbacks need an efficient funneling system to deposit their prey directly into their stomach, because with nearly zero nutrients in a jellyfish, the turtle needs to consume around 73 percent of its body weight every day. That's a lot of time spent chasing jellyfish that the turtle can't waste on inefficiency.

Unfortunately, the turtle can't tell the difference between jellyfish and plastic bags, so the cute and cuddly leatherback turtle is facing extinction from floating debris. And that sucks, because it's just as important to preserve nature's horror as it is to preserve its beauty. It reminds us of who's in charge.

Getty

You already know piranhas as the little ravenous balls of teeth that eat everything, but have you ever wondered what eats piranhas? We're glad you asked! Meet the payara, also known as the "vampire fish." That up there with it is Jeremy Wade, a British biologist who apparently isn't too attached to his nose.

You have to be toting some pretty hardcore weaponry to survive in the Amazon, and the vampire fish is packing a mouth full of knives designed to shank other fish prison-yard style. The teeth are so long -- up to 6 inches -- that it has to sheathe them in a holster built into the front of its face.

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They are closely related to piranhas, and piranhas also constitute most of their diet. It's like a monster that has evolved to eat other monsters. And while there have been no reports of a payara stabbing people in the kidneys and making off with their wallets, it's probably still a good idea not to go into the water.

Imagine you're alone in the dark, briny depths of the ocean, detached from the rest of your diving team, with nothing but heavy blackness and silence all around you. Then, quietly at first, you hear the sound of high-pitched voices approaching you. "Come play with us!" they say. "We want to be friends!"

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Appearing only in deep water under cover of night, the cookie cutter shark is only 2 feet long, but it has the largest teeth relative to its size of any shark, contorting its face into a terrifying Bond-villain smile.

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As small as it is, the cookie cutter prefers to inflict hit-and-run attacks. As its name suggests, its signature move is to use the razor-sharp cookie cutter built into its face to quickly rip a circular chunk out of whatever tasty piece of flesh it comes across. Like the Flash, but attacking you with a melon baller. That's why its victims wind up looking like this:

Wikipedia

And they're not picky about what they clamp onto. Whales, dolphins, other sharks and even submarines bear the circular scars of cookie cutter attacks. And in 2009, marathon swimmer Michael Spalding came out of the water after a midnight swim with an inch deep circular piece missing from his leg. Thanks, Mike. Now they know what we taste like.

Once you start the journey into the center of a penguin, it's teeth all the way down. There are teeth in their beaks, teeth on their cheeks, teeth on their tongues, and probably teeth on the backs of their eyeballs if you ever care to check (we don't recommend it).

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Because penguins swallow their food alive and wriggling, they need some way to both keep hold of their prey and maximize its suffering. The penguin's spiny tongue and mouth parts work like a conveyor belt to keep things moving in one direction -- and it's not someplace anyone wants to go.

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We already have a lot of respect for the woodpecker for having the highest density of dick references in a single name, but while we're discussing large, phallic protrusions, check out the woodpecker's tongue, which suggests that it is definitely compensating for something.

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The woodpecker basically has a gaffing hook for a tongue. Not only is it up to three times the length of the bird's beak, but it's tipped with a barbed spearhead that impales bugs in trees and drags them screaming to their end.

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You might be wondering how the woodpecker keeps this whole thing inside its head. Even if you weren't wondering that, we're going to tell you anyway. You see, when it's not using it to stab things, the woodpecker wraps its entire tongue around the back of its skull, behind its eyeball, and then back into its nostril, like so:

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Every party has that one guy who's all "Hey, look what I can do!" Woodpecker parties are full of those guys.

Why would nature do this to us? Well, it's the same reason we have them -- teeth like ours are able to chew anything, and unusually for a fish, their favorite foods are seeds and nuts.

You'd be tempted to make a bad joke here about "keeping your nuts out of the Amazon River," at which point we'd be forced to tell you that, all jokes aside, the pacu will in fact eat your testicles. That's why Papua New Guineans have nicknamed it the "ball cutter."

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The pacu was introduced to Papua New Guinea in the 1990s to provide a local food source (because people just love eating something that looks like man contorted into an eternal scream), and since then, the "nut"-eating bastards have been credited with the deaths of at least two men in the region from a combination of blood loss and shame. Happy swimming, guys.

The Telegraph

Monte Richard is a columnist at DaftGadgets.com, Warren Tilson has a book, and E. Reid Ross lives in the Craption Forums.

For more nightmare fuel, check out 7 Terrifying Giant Versions of Disgusting Critters and 7 Terrifying Prehistoric Creatures (That Are Still Around).