Specialised features of Sharks - Skeleton
A sharks skeleton is made from cartilage - not bone.
This allows them greater flexibility and range of motion. The cartilage provides a lightweight internal frame which allows faster movement through the dense medium of water.
In areas where extra strength or support is needed, such as the jaw and backbone, the cartilage in these parts has been calcified - which means it has been strengthened with a layer of tiny calcium crystals to make it even stronger.
Some species have several layers of calcification to give extra strength, the Great White Shark having the most, between 3-5 layers, giving it exceptional jaw strength.
The supporting rays in the fins are made from collagen.