The most common sharks found around the Maltese Islands and the Mediterranean sea : guide book

Abstract

What is a shark? Sharks are amazing fish that have been around long before the dinosaurs existed. They live in waters all over the world, in every ocean and even in some rivers and lakes. Unlike other fish, sharks have no bones, their skeleton is made of cartilage, which is a tough, fibrous substance, nearly as hard as bone. Evolution of sharks: Sharks have existed for over 450 million years. They evolved over 100 million years before the dinosaurs did. This was long before people evolved. Most fossil evidence of early sharks is from fossilised teeth. Cladodonts, primitive sharks, had double-pointed teeth, were up to 3 feet (1m) long fish-eaters and lived about 400 million years ago. Modern forms of sharks evolved during the Jurassic Period about 150 million years ago. This was the time of the giant dinosaurs like Brachiosaurus. [excerpt]