Hagfish appear to have branched off from the chordates before the vertebral column appeared (Lee 2002).
Extant hagfish have paddle-like tails, cartilaginous skulls, and tooth-like structures composed of keratin.
There have been claims that the hagfish eye is significant to the evolution of more complex eyes (UQ 2003).
Hagfish are important in food chains, serving as scavengers, while themselves being consumed by seabirds, pinnipeds, and crustaceans (Lim et al.
There has been long discussion in scientific literature about the hagfish being classified as vertebrates versus invertebrates.
The extant hagfish average about half a meter (18 inches) long.
Scientists are exploring possible practical applications for the hagfish slime (Vowles 2007).
Others, however, place Vertebrata and Craniata as synonyms at the same level of classification, and thereby retain hagfish (Myxini) as members of the superclass Agnatha within the vertebrates (Nelson 1994).
Hagfish do not have a larval stage, in contrast to lampreys, which have a long larval phase.
Given their classification as Agnatha, Hagfish are seen as an elementary vertebrate in between Prevertebrate and Gnathostome.
The hagfish family, Myxinidae, is the only family in the order Myxiniformes (also known as Hyperotreti), which itself is the only order in the class Myxini.
Hagfish have no true fins and have six barbels around the mouth and a single nostril.
No other slime secretion known is reinforced with fibers in the same manner as hagfish slime.
The circulatory systems of the extant hagfish have both closed and open blood vessels, with a heart system that is more primitive than that of vertebrates, bearing some resemblance to that of some worms.
The "sphinx" Narasimha is part of the Buddhist tradition and functions as a guardian of the northern direction and was also depicted on banners.
Hagfish are consumed in some regions of the world, being particularly important commercially in Korea (Lee 2002).
Hagfish typically are scavengers, entering decaying and dead fish and invertebrates (including (polychaete marine worms and shrimp), feeding on the insides.
Extant hagfish are long, vermiform (worm-like), and can exude copious quantities of a sticky slime or mucus (from which the typical species Myxine glutinosa was named).
Hagfish are jawless and generally classified with the lampreys into the superclass Agnatha (jawless vertebrates) within the subphylum Vertebrata.
An adult hagfish can secrete enough slime to turn a large bucket of water into gel in a matter of minutes.
A single fossil of hagfish shows that there has been little evolutionary change in the last 300 million years (Marshall 2001).
Hagfish tend to burrow under rocks or into mud, in highly saline waters, and away from bright light (Lee 2002).
Extant hagfish are placed in the family Myxinidae within the order Myxiniformes (Hyperotreti) and subphylum or class Myxini.
Hagfish are the only animals that have a skull but not a vertebral column.
Janvier (1981) and a number of others put hagfish in a separate subphylum Myxini, which along with the subphylum Vertebrata comprises the taxon Craniata, recognizing the common possession of a cranium (Janvier 1981).
Hagfish have a scaleless, elongated, eel-like body without paired fins.