<P> Cartilaginous fishes, class Chondrichthyes, consisting of sharks, rays and chimaeras, appeared by about 395 million years ago, in the middle Devonian, evolving from acanthodians . The class contains the sub classes Holocephali (chimaera) and Elasmobranchii (sharks and rays). The radiation of elasmobranches in the chart on the right is divided into the taxa: Cladoselache, Eugeneodontiformes, Symmoriida, Xenacanthiformes, Ctenacanthiformes, Hybodontiformes, Galeomorphi, Squaliformes and Batoidea . </P> <Table> External video <Tr> <Td_colspan="2"> Chordate Evolution and Bony Fish YouTube </Td> </Tr> </Table> <Tr> <Td_colspan="2"> Chordate Evolution and Bony Fish YouTube </Td> </Tr> <P> Bony fishes, class Osteichthyes, are characterised by bony skeleton rather than cartilage . They appeared in the late Silurian, about 419 million years ago . The recent discovery of Entelognathus strongly suggests that bony fishes (and possibly cartilaginous fishes, via acanthodians) evolved from early placoderms . A subclass of the Osteichthyes, the ray - finned fishes (Actinopterygii), have become the dominant group of fishes in the post-Paleozoic and modern world, with some 30,000 living species . </P>

The group of fish that were the ancestors to amphibians was