Hagfish, the class
Myxini (also known as
Hyperotreti), are
eel-shaped, slime-producing marine fish (occasionally called
slime eels). They are the only known living animals that have a
skull but no
vertebral column. Along with
lampreys, hagfish are jawless; they are the sister group to vertebrates, and living hagfish remain similar to hagfish from around 300 million years ago.