The sea lamprey, Petromyzon marinus, which is a descendant of the earliest known type of vertebrates, is a parasitic species of eel-like fish native to the Atlantic Ocean and the East Coast of North America. Because of their eel-like shape, lamprey are sometimes confused with eels, but they are not eels at all. Lampreys, unlike an eel, have no jaws, no true teeth, no paired fins and a skeleton made of cartilage, not true bone.