Hagfish

Hagfish are jawless fish that have existed for over 300 million years and are among the most primitive vertebrates still alive today. These slimy deep-sea creatures are famous for their ability to produce enormous amounts of protective mucus when threatened, which allows them to escape predators and suffocate attackers by clogging their gills. With their eel-like bodies, tooth-like structures made of protein rather than bone, and a diet consisting mainly of dead animals on the ocean floor, hagfish represent a fascinating living link to the ancient origins of all vertebrate life.