Class Chondrichthyes

Also see:
Class Chondrichthyes Fossil Gallery

Class Chondrichthyes comprises the jawed, cartilaginous fish with a flexible skeleton made of cartilage rather than bone. Since appearing on earth some 450 million years ago, some members of class Chondrichthyes, notable the sharks, have been and remain among the fiercest and successful of predators. Their success that has not only assured their survival, but has required their minimal evolutionary adaptation over the eons to assure survival. Sharks have a good sense of smell but poor eyesight. To compensate for the poor eye site, they have a lateral line system of sensory organs running down the side of the body that can detect very small changes in water pressure as would be made by a fish swimming nearby. Skates and rays are other examples of cartilaginous fish that consists of about 1,000 extant species.

Order Lamniformes contains the extinct Megalodon (Carcharodon megalodon) which like all extinct sharks is only known by the fossil teeth. Shark fossils are extremely rare, in general, because cartilage fossilizes very poorly. Their teeth, however, are made of a bone-like material coated with hard enamel and they fossilize very well.