Chondrichthyans have toothlike scales called dermal denticles or placoid scales. They were probably derived from a fusion of placoid scales. The entire body is covered by an exoskeleton of placoid scales. The dermis is covered with separate dermal placoid scales. Shark skin is almost entirely covered by small placoid scales. Cartilaginous fishes (sharks and rays) are covered with placoid scales. It is only known from placoid scales discovered in Russia before 1973. The skin is only slightly rough and the placoid scales are small. Placoid scales are found on cartilaginous fish including sharks. The teeth are modified placoid scales that are regularly shed and replaced. Placoid (pointed, tooth-shaped) scales are found in the cartilaginous fishes&colon; sharks, rays. Their skin is covered in placoid scales "(dermal denticles)" that are as rough as sandpaper. Placoid scales have a pointed tip that is oriented caudally and are homologous to teeth. There are yellow-white placoid lesions in the posterior pole at the level of the RPE.