The fishes are the most numerous and diverse of the vertebrate groups, stemming from a long and branched line of ancient ancestry. Though they account for more than half of the world's total vertebrate species, they have essentially retained the same anatomical plan for 450 million years (Maisey, 1996). What accounts for the stamina of these living fossils? During their evolutionary history, fishes have given rise to a vast diversity of forms, not merely to survive but also to compete, they have colonized an extraordinary range of habitats, and their sheer numbers are nearly enough to…
