Class: Chondrichthyes Subclass: Elasmobranchii Superorder: Selachimorpha Orders Carcharhiniformes Heterodontiformes Hexanchiformes Lamniformes Orectolobiformes Pristiophoriformes Squaliformes Squatiniformes Sharks are a group of fish characterized by a cartilaginous skeleton , five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are