hagfish

• They have no jaws. Instead, they have two raspers above their tongue.
• They are functionally hermaphroditic, meaning that while they have both male and female sex organs, they mature as one or the other, but have the capacity to change.
• They have an incredibly low metabolism, and may need to eat only once every couple of months.
• They can be found in great numbers in the colder ocean waters of the northern and southern hemispheres.
• It is now known that while they do consume dead or dying fish, their diet consists principally of marine worms and invertebrates.
• Despite the fact that they may be the most repulsive species of fish, over 5 millon pounds of hagfish is consumed annually in Korea.

Hagfish are not actually fish, they're not even vertebrates, but are actually our closest non-vertebrate cousins. Both vertebrates (like you and me) and hyperotreti (the group to which hagfish belong) are in the phylum chordata (animals with spinal cords) and are further grouped together in the taxon craniata (animals with skulls). Hagfish are then separated from vertebrates into hyperotreti because they have no backbones. The lineage looks like this:

            =    ?====== Calcichordata
            |
Chordata ===|  ========= Urochordata
            |  |
            ===|     === Cephalochordata
               |  ===|
               ===|  === Yunnanozoon  
                  |                   === Hyperotreti (hagfishes)
                  ====== Craniata ====|
                                      === Vertebrata (lampreys and jawed vertebrates)

Hag"fish`(- fish`),n.(Zoöl.)

See Hag, 4.

© Webster 1913