What is a Shark ?

Sharks and Rays are fish. They have a backbone or vertebral column and jaws like fish however they have very different body plans to most fish found in the sea.

Sharks and Rays belong to a class of fishes known as the Chondrichthyes meaning cartilaginous fishes. Belonging to an early lineage of early development, the Chondrichthyes have evolved and diverged over a much larger time period then their cousins the bony fish. Roughly 400 million years of evolution has been packed into their bodies. They get their name from their internal skeleton that is comprised entirely of cartilage, a dense connective tissue that is not penetrated by blood vessel. This substance is much more flexible than bone. Humans have cartilage in our ears and our nose. Cartilage alone however is not rigid enough and so various parts of the Chondrichthyes skeleton have been rigidified by layers of minerals (calcium carbonate) around the areas that need the most support such as the vertebral column and the jaws.

Bony fish by comparison as their name implies have bone for an internal skeleton that unlike cartilage is penetrated by blood vessels. In addition bone is far more rigid than cartilage although less flexible. The Chondrichthyes are a Class of fish in which there are two sub-classes, the Elasmobranchs (modern sharks, skates and rays) and the Holocephali (ratfish and chimaeras)

To see a video of a genuine shark dissection performed by Dr Jeffrey Graham please click here.

This video is of an actual shark dissection and therefore is very graphic. Viewer discretion is advised.