According to the Shark Trust, sharks, skates and rays all belong to a subclass of Chondrichthyes known as the Elasmobranchii. The class Chondrichthyes consists of fish-like marine animals that have skeletons made up of cartilage rather than bone.
The Fishery Bulletin of the Fish and Wildlife Service notes that the other subclass in Chondrichthyes, Holocephali, are closely related animals that are known as chimaeras. The group to which sharks, skates and rays belong is distinguished from these creatures by having asymmetrical tail fins and multiple gill openings. While sharks belong to the infraclass Selachii, rays and skates belong to the infraclass Batoidea.