Concealed Weapons: Erectile Claws In African Frogs

Certain frogs of Central Africa possess bizarre defensive weapons.



Unlike the claws of most vertebrates, which are externally visible and attached to the digit tip, the bony claws of these frogs lie hidden. There is no keratinous covering and the sharp, curved bone is concealed entirely within the toe.



To become functional, the claw is flexed causing the tip to break free from connections within the toe and pierce through the frog's skin.



Confronted by a predator or picked up by a human, these frogs expose their concealed weapons and with powerful thrashing and kicking, readily draw an adversary's blood.



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