Hagfish are eel-like creatures with soft, slimy skin. They have a single nostril and a mouth that is surrounded by four pairs of barbels. Hagfish are scavengers and feed on dead or dying fish and other animals.
Lampreys are also eel-like creatures, but they have a more streamlined body and a sucker-like mouth. Lamreys are parasites and feed on the blood of other fish. They attach themselves to a fish and then use their teeth to cut through the fish's skin and suck its blood.
Ostracoderms were an extinct group of jawless fish that lived from the Ordovician to the Devonian periods. They were covered in bony plates and had a variety of body shapes. Ostracoderms were likely the ancestors of modern jawed fish.
Jawless fish are an important part of the marine ecosystem. They play a role in the food chain and help to clean up dead animals. Jawless fish are also a source of food for some humans.