Evolution of fishes

FISH

Fishes evolved from the free-swimming larval forms of their chordate ancestors approximately 500 million years ago. These first fishes were jawless, boneless and limbless bottom feeders which later evolved into an extremely diverse group of organisms in terms of morphology, physiology, behaviour and ecology. In the half a billion years since their appearance, fish have risen from obscurity to become the most successful group of vertebrates on the planet today. This section outlines some of the major groups of fishes and charts their evolutionary history.

This timeline indicates the approximate timeframe that each group enjoyed high success, though fossil evidence suggests that some groups (the ostracoderms and chondrichthyans in particular) may have been present much earlier . The approximate date that each period began is expressed at the bottom of the timeline in millions of years before present.