The Spanish ribbed newt has an unusual method of protecting itself: when presented with an attacker, the newt can pierce its own skin with its rib bones, allowing it to stab a predator and deliver a dose of deadly poison.
Naturalists have known for well over a century that the ribbed newt is capable of exposing its sharply pointed ribs when threatened, but it is only recently that zoologists at the University of Vienna have looked into the mechanism by which the creature protects itself. Using x-ray imaging, the zoologists have determined that the newt is able to move its rib cage while keeping the rest of its body still, creating enough pressure for the newt to pierce its own skin, so that the ribs can be used as a weapon against would-be predators.
Much like the X-Men mutant Wolverine, the ribbed newt is able to pop its bones back inside its body and quickly heal the skin after an attack, but this amphibian has an extra feature Logan doesn't. When stressed, it secrets a highly toxic poison, which coats the points of the rib bones as they pierce the skin. Thus, the ribs can deliver a quick shot of poison to any animal that tries to grab the newt, leaving the attacker to retreat in great pain.