Unlike the animals mentioned by Ratter14 the tuft at the end of the lions tail hides a "spur" of bone, which is separate from the other bones in the tail. Its function is not known, and it is not present in all lions. It was once believed to be a remnant of a claw that existed in ancient lions, but then disappeared. Scientists think it may have been used to help grasp the prey. (Source L�Afrique de Marmol)