The Hairy Bone-breaker
We usually don't like to have repeats on a list, but this frog – Trichobatrachus robustus, otherwise known as a hairy frog -- deserves to share space with other superhero animals. But no young, handsome leading man would ever want to be cast in the film adaptation of this super animal's story. The male hairy frog is horrifyingly ugly and sprouts hair-like threads of skin and arteries during mating season. Because the ladies love that.
His superpower is equal parts disturbing and awesome. When threatened, the frog can puncture claws out of his toe pads, just like Wolverine. Instead of cat or dog claws made of keratin, the hairy frog's claws are bone. More disturbingly, the frog appears to have to break the bones of its toes in order to push the claw out [source: Brahic]. Put it like that, and Wolverine suddenly seems more villain than hero.
Scientists can't figure out how the bone retracts, and they posit that the amphibian is regenerating tissue to help the wound heal. Which is really all you need to know to launch a thousand nightmares: a Wolverine frog with regeneration powers.