The hagfish is a jawless fish that feeds on dead or injured fish. The lamprey, another jawless fish, attaches itself to a living fish to feed on its body fluids.
Lampreys and hagfish belong to the superclass Agnatha, which means "no jaws" in Greek. They are primitive vertebrates with skeletons made of cartilage and have notochords, flexible rod-shaped structures supporting the length of the body, rather than true spinal columns. Both hagfish and lampreys have very sharp teeth and use them to shred flesh. Their origins date back about 530 million years; modern hagfish are similar to fossil specimens dating back 300 million years.