Cartilaginous fish are characterized by a skeleton made of cartilage instead of a bone, jaws, and symmetrically paired fins, gills, and paired nostrils. These fish generally have tough skin covered with modified teeth called 'dermal denticles'. These provide protection and also help to streamline the fish.
There are at least 1100 known species of cartilaginous fish, which include sharks, rays, skates and sawfish and ghost sharks (or chimeras).