The animation is not very exciting, but the discovery of this fish is. Broadly speaking, fish fall into two groups: jawless fish (only a small number of living species, including the lamprey, but once the only type of fish), and the jawed fish, which includes the vast majority of the fish. The jawed fish can also be divided into two groups: the bony fish, which is the majority of fish, including our own ancestors, and the cartilaginous fish, which are sharks, rays, skates and chimaeras. This creature has just been found, and is a very old member of the cartilaginous fish, so related to modern sharks, and is the oldest known jawed fish, as they say it lived 420 million years ago.