Hagfish, of the class Myxini / mɪkˈsaɪnaɪ / (also known as Hyperotreti) and order Myxiniformes / mɪkˈsɪnɪfɔːrmiːz /, are eel -shaped jawless fish (occasionally called slime eels). Hagfish are the only known living animals that have a skull but no vertebral column, although they do have rudimentary vertebrae. [3]