'Acanthodians are not at all shark-like in shape, for example they have diamond-shaped scales and spines in front of all the fins,' says Emma. Described as the 'least shark-like shark', it is thought to have risen from within a group of fish known as acanthodians or spiny sharks. The earliest shark-like teeth we have come from an Early Devonian (410-million-year-old) fossil belonging to an ancient fish called Doliodus problematicus. It was also around this time that the first plants invaded the land. As there are no fossils of these animals from this period of time, this is based solely on the DNA and molecular evidence of modern sharks and chimaeras. Scientists are still debating if these were true sharks or shark-like animals.'ДЄnalysis of living sharks, rays and chimaeras suggests that by around 420 million years ago, the chimaeras had already split from the rest of the group. If these were from sharks it would suggest that the earliest forms could have been toothless. The earliest fossil evidence for sharks or their ancestors are a few scales dating to 450 million years ago, during the Late Ordovician Period.Д®mma Bernard, a curator of fossil fish at the Museum, says, 'Shark-like scales from the Late Ordovician have been found, but no teeth. While often referred to as living fossils, sharks have evolved many different guises over the hundreds of millions of years that they have been swimming the oceans.

The group includes the more famous animals such as whale sharks and great whites, but also all rays, skates and the little-known chimaeras (also known as ratfish, rabbit fish or ghost sharks). The only part of their skeleton not made from this soft, flexible tissue is their teeth. Sharks belong to a group of creatures known as cartilaginous fishes, because most of their skeleton is made from cartilage rather than bone.

First sharks 3d