Sharks belong to the clade Selachimorpha in the subclass Elasmobranchii in the class Chondrichthyes. The Elasmobranchii also include rays and skates; the Chondrichthyes also include Chimaeras. It was thought that the sharks form a polyphyletic group: some sharks are more closely related to rays than they are to some other sharks,[21] but current molecular studies support monophyly of both groups of sharks and batoids.[22][23]
The clade Selachimorpha is divided into the superorders Galea (or Galeomorphii), and Squalea (or Squalomorphii). The Galeans are the