The Hairy Frog
Also called the horror frog and the Wolverine frog, the hairy frog sprouts claws on its hind feet. These aren't "true" claws because they lack a keratin coating, and are made entirely of bone. They emerge through the toe pads when the frog contracts a specific muscle, forcing the claws downwards and breaking the collagen bond between them and the toe bones.
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Key Facts In This Video
The hairy frog breaks its own bones to force keratin claws through its skin. 00:21
The bones break when the frog feels threatened and contracts a muscle that moves the claws downward. 00:35
Scientists theorize that the frog retracts the claws back into its body when its muscles relax. 00:50