 Claws grow out of the third phalanges of the paws and are made of keratin.Many predatory mammals have protractile claws that can partially hide inside the animal's paw, especially the cat family, Felidae, almost all of whose members have fully protractible claws.Outside of the cat family, retractable claws are found only in certain species of the Viverridae (and the extinct Nimravidae).