What is Hagfish?
{{Taxobox | name = Hagfish | image = Pacific_hagfish_Myxine.jpg | image_caption = Pacific hagfish resting on bottom<br />280&nbsp;m depth off [[Oregon]] coast | regnum = [[Animal]]ia | unranked_superclassis = [[Craniata]] | superclassis = [[Cyclostomata]] | classis = '''Myxini''' | ordo = '''Myxiniformes''' | familia = '''Myxinidae'''}} '''Hagfish''' are [[craniates]] in the superclass [[Cyclostomata]], class '''Myxini'''. Hagfish do not have a skeleton, except they do have a [[skull]], which is made of [[cartilage]]. Because of this, many researchers think Myxini should not be in the [[phylum|subphylum]] [[Vertebrata]].<ref>Neil A. Campbell and J.B. Reece 2005. ''Biology''. 7th ed, Benjamin Cummings, San Francisco CA.</ref> However, because of its fins and [[gill]]s, they are called fish. They are marine, meaning they live in the sea. The original 19th century classification groups hagfish and lampreys together as [[cyclostomata|cyclostomes]] (or historically, [[Agnatha]]), as the oldest surviving class of [[vertebrates]] alongside [[gnathostomata|gnathostomes]] . An alternative scheme proposed that jawed vertebrates are more closely related to lampreys than to hagfish, so vertebrates include lampreys but exclude hagfish. Recent DNA evidence supports the original scheme.<ref name=r3>{{cite journal|author=Janvier P. |year= 2010|title=MicroRNAs revive old views about jawless vertebrate divergence and evolution|journal= Proceedings of the National Academy of Sciences |volume=107|pages=19137–19138|quote=Although I was among the early supporters of vertebrate paraphyly, I am impressed by the evidence provided by Heimberg et al. and prepared to admit that cyclostomes are, in fact, monophyletic. The consequence is that they may tell us little, if anything, about the dawn of vertebrate evolution, except that the intuitions of 19th century zoologists were correct in assuming that these odd vertebrates (notably, hagﬁshes) are strongly degenerate and have lost many characters over time|doi=10.1073/pnas.1014583107|issu