Some fish have bones, including full backbones and articulated skeletons, while other fish do not have bones. The bony fish, as they are known, belong to the class Osteichthyes. The other class of fish is known as Chondrichthyes, which includes cartilaginous fish like sharks and rays.
The bony fish of class Osteichthyes are the largest class of vertebrates in the animal kingdom, with more than 20,000 species known to man. Bony fish fall into two subcategories: the ray-finned fish and the lobe-finned fish. Ray-finned fish make up the vast majority of known living fish species as of July 2014; the coelacanth, once thought to be an extinct prehistoric fish, is the only known living lobe-finned bony fish.