Hagfish

Hagfish Temporal range: Late Carboniferous–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Sixgill hagfish, Eptatretus hexatrema
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Superclass:	Cyclostomi
Class:	Myxini
Order:	Myxiniformes
Family:	Myxinidae Rafinesque, 1815
Type species
Myxine glutinosa Linnaeus, 1758
Genera[1]
Order Myxiniformes † Myxinikela Bardack, 1991 Family Myxinidae Rubicundinae Fernholm et al., 2013 Rubicundus Fernholm et al., 2013 † Tethymyxine Miyashita et al., 2019 Eptatretinae Bonaparte, 1850 Eptatretus Cloquet, 1819 Myxininae Nelson, 1976 Myxine Linnaeus, 1758 Nemamyxine Richardson, 1958 Neomyxine Richardson, 1953 Notomyxine Nani & Gneri, 1951
Synonyms
Bdellostomatidae Gill, 1872 Homeidae Garman, 1899 Paramyxinidae Berg, 1940 Diporobranchia Latreille, 1825[2]

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] Hagfish are marine predators and scavengers^[4] who can defend themselves against other larger predators by releasing copious amounts of slime from mucous glands in their skin.^[5]

Although their exact relationship to the only other living group of jawless fish, the lampreys, was long the subject of controversy, genetic evidence suggests that hagfish and lampreys are more closely related to each other than to jawed vertebrates, thus forming the clade Cyclostomi.^[6] The oldest-known stem group hagfish are known from the Late Carboniferous, around 310 million years ago,^[7] with modern representatives first being recorded in the mid-Cretaceous around 100 million years ago.^[6]