Claw
A primate's nail only has the unguis; the subunguis has disappeared. Similar to the tail, the claw in apes is not needed. However, in some primates, the subunguis has redeveloped to make a claw-like structure. These certain animals do not have actual claws; instead the unguis appears normal along with a thick growth of subunguis.  Some lemurs have a toilet-claw which they use for scratching and grooming.