Vertebrates - Sharks

Creatures of this class are characterised by a cartilaginous skeleton made up of tiny, calcified prisms. Living examples include the Sharks, Skates, and Rays. Cartilage is not usually preserved, so common fossils tend to be teeth, scales, and dorsal-fin spines. Sharks’ teeth are continuously replaced from behind, being shed from the jaw margin or lost during feeding.  Chondrichthyans diversified from Devonian (period) origins to become very common in today’s sea.