‘Biologists at Harvard University have determined that some African frogs carry concealed weapons: When threatened, these species puncture their own skin with sharp bones in their toes, using the bones as claws capable of wounding predators. [..]
“It’s surprising enough to find a frog with claws,” says Blackburn, a doctoral student in Harvard’s Department of Organismic and Evolutionary Biology. “The fact that those claws work by cutting through the skin of the frogs’ feet is even more astonishing. These are the only vertebrate claws known to pierce their way to functionality.”
“Most vertebrates do a much better job of keeping their skeletons inside,” he adds.
Blackburn first became aware of the clawed frogs while conducting fieldwork in the central African nation of Cameroon. When he picked up one of the hulking fist-sized frogs, it flailed its hind legs violently, scratching him and drawing blood.’