What do you think of this frog? Kind of cute, you think? Perfectly harmless, you think? Not at all like the living embodiment of the Saw movies, you think? Well, you're wrong. The "horror frog" more than lives up to its nickname.

Officially, this is called the hairy frog, and it's easy to see why. The "fur" you see growing out of its sides isn't really fur. The hairs are little fleshy strands, kind of like the papillae you have on the top of your tongue. Scientists think that they help the hairy frog absorb oxygen from the water.

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But it's not these little hairs that give Trichobatrachus robustus its nickname. The "horror frog" earns its name when it is threatened. At first, when scientists picked up these frogs and received a scratch, they thought that it had retractable claws. It does not have claws, retractable or otherwise. It makes claws. It does so by breaking the bones in its hands and feet and shooting the bone fragments out through its own skin. It does all this on the off chance that these broken bone claws can cause the kind of damage that would deter a predator. Can anyone reading this really say they want to live that much?

Evidently, this strategy works. The claws provide enough of an evolutionary edge that the "wolverine frog" — and yes, that is another one of its nicknames — has a special muscles that facilitates the breaking of its bones and the extension of the bone out through its toe pads.

Image: Proceedings of the Zoological Society of London 1901

[Source: Horror Frog Breaks Its Own Bones To Produce Claws.]