How long has there been sharks?

The history of sharks dates back over 400 million years. They are one of the oldest forms of life still in existence today, and have lived continuously since the Silurian period of the Paleozoic era. Sharks have evolved over millions of years, with over 500 different species existing today. They range in size from the smallest, the cookiecutter shark, which is only 6.5 inches long, to the largest, the whale shark, which can reach up to 40 feet in length. Sharks can be found in all oceans of the world, from the shallows of the continental shelves to the deep waters of the open ocean.