"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.
Vertebrate claws are used in a variety of important behaviours and are typically composed of a keratinous sheath overlying the terminal phalanx of a digit. Keratinous claws, however, are rare in living amphibians; their microstructure and other features indicate that they probably originated independently from those in amniotes. Here we show that certain African frogs have a different type of claw, used in defence, that is unique in design among living vertebrates and lacks a keratinous covering.
Storytellers: David C. Blackburn, James Hanken, Farish A. Jenkins - Dept. Organismic and Evolutionary Biology Harvard University
When Threatened, A Few African Frogs Can Morph Toes Into Claws