Hairy (Wolverine) Frog

This small four-inch amphibian is a resident of Western Africa. What is so strange about this frog, is the manner in which it will defend itself when it encounters a predator. When threatened, it will contract the muscles in its hind legs so forcefully that it causes the bones to break and protrude through its skin. The result is a cat-like appearance of their toe pads with extendable claws. After having defended itself successfully the bones once again retreat back into the frog and it is believed the connective tissue helps the bone to regenerate until the next attack. This regenerative process is common in amphibians.

 

https://www.newscientist.com/article/dn13991-horror-frog-breaks-own-bones-to-produce-claws/