Decline and fall of the ostracoderms
The reign of the ostracoderms began its decline toward the beginning of the Devonian Period,with the advent of the first real fish, real fish, endowed with upper and lower jaws and, therefore quite capable of hunting, killing and devouring their prey. The first of these real fish were the placoderms ( plated skins) ,followed by the accanthodian (spiny fish), about whome we shall have more to say later. Slowly but, inevitably.they all disappeared. Except for a small thy all disappeard,Except for a small group group that still lived on today, the cyclostomes(round mouths). Only a few members if the great agnatha empire still live today,in two very different orders of cyclostomes the myxinoids or hagfish, and the petromyzons, or lampreys.