Chondrichthyes (Cartilaginous fishes)
Chondrichthyes (Huxley, 1880) is a group of jawed fish with paired fins and nostrils. They have scales and further are their hearts two-chambered. They differ significantly in having a skeleton made of cartilage rather than bone. The group is divided in the two subclasses: Elasmobranchii (sharks, rays and skates) and Holocephali (chimaeras, sometimes called ghost sharks).
There exists around 800 described species of chondrichthyes.