CAMBRIDGE, Mass., June 25 (UPI) -- U.S. scientists have found 11 African frog species whose toes can morph into claws -- the only vertebrate claws known to pierce their way to functionality.
Harvard University biologists say the frogs, when threatened, can 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," said doctoral student David Blackburn. "The fact that those claws work by cutting through the skin of the frogs' feet is even more astonishing."
Blackburn said he became aware of the clawed frogs while conducting fieldwork in Cameroon. When he picked up one of the fist-sized frogs, it flailed its hind legs violently, scratching him and drawing blood.
He subsequently examined museum specimens of 63 African frog species and found 11 in which the bones at the ends of the toes were pointed and hooked, with smaller, free-floating bones at their tips.
The research conducted by Blackburn, James Hanken and Farish Jenkins Jr. is to appear in a forthcoming issue of the journal Biology Letters.
