Class: Chondrichthyes

The Class of Chondrichthyes are denoted most notably by their internal skeleton that unlike our own bone is made up of Cartilage. This is a substance that is much more flexible and lighter than bone. Humans possess it in the tops of our ears and the end of our nose. However Shark Cartilage is unlike our own containing minerals that we have in our bone. The main result of this is that sharks skeletons decompose upon their death extremely rapidly. Consequently fossils of past sharks are difficult to come by, their teeth however are extremely hard and fossilize well, they also regularly lose them although they are replaced. These two facts make sharks teeth are one of the main sources of information about extinct sharks.

They are divided into two groups, the Holocephali (Chimaeras) a group of deep sea fish and the Elasmobranchii (the group that includes all the modern sharks, rays and skates.)

Kingdom: Animalia

Phylum: Chordata

Sub-Phylum: Vertebrata

Class: Chondrichthyes