Many Scientists believe sharks came intop existence 400 million years ago. That is almost 200 million years before dinosaurs. Fossil records have shown over 3,000 shark species over the years.One fossil tooth belonged to a Megalodan Shark, the worlds largest ever shark. The tooth on its own was 17cm in length.Sharks dominated the top of the marine food chain along with Mosasaurs and Plesiosaurs.
This is the period in time that saw single celled organisms transform into fish and sharks through evolution. Most sharks evolved in different ways with crazy appendages. There are no sharks that lived in the Plaeozoic era alive today.
There were a couple of sharks that survived from the Paleozoic era and stayed in the Mesozoic era. The Mesozoic era consists of the Triassic, Jurassic, and Cretaceous periods. There was a rapid increase in shark species during the Jurassic period.Here is where all modern shark families evolved the most. But it did not stay that way, the Mesozoic era is also where many marine animals died out.
In the Cenozoic era or present day sharks and toothed whales continue to stay at the top of the aquatic food chain.The last modern shark to evolve were the Hammerhead sharks. The Sharks alive today have survived 5 mass extinctions.