Chondrichthyes

Chondrichthyes ( /kɒnˈdrɪkθi.iːz/; from Greek χονδρ- chondr- 'cartilage', ἰχθύς ichthys 'fish') or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, a two-chambered heart, and skeletons made of cartilage rather than bone. The class is divided into two subclasses: Elasmobranchii (sharks, rays and skates) and Holocephali (chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class).