Chordates possessing and .

By extension, more chordates lack heads or, more precisely, and other head-associated features. The Myxini, or hagfish, are the most primitive of the Craniates.

Subphylum Vertebrata is at least potentially a subset of the Craniata, that is, if heads among chordates came to be prior to the evolution of the . That contention is not at all certain, however, as hagfish in particular may have instead descended from ancestors.

To the extent that hagfish are indeed fish, then the craniates can viewed as fish along with all of their descendants.