|CHORDATA - The Chordates|
o Chordata |--Urochordata | |--Larvacea | `--+--Ascidiacea | `--Thaliacea `--+--Cephalochordata `--+--Haikouella `--o Craniata |--Myxinoidea `--Vertebrata
The Craniata is the clade uniting the hagfish (Myxinoidea) and the vertebrates. It is named for the skull (cranium), which among extant animals is restricted to these animals, although it is likely that the immediate ancestors and cousins of the craniates - stem-craniates or "craniatomorphs" - also had skulls. Note that skulls originally, as in hagfish and basal vertebrates, were wholly of cartilage and without bone.
Early craniates include Haikouichthys and Myllokunmingia from the Cambrian of China. Haikouella has been suggested as a craniate, but is probably a "craniatomorph" or even further down on the deuterostome tree, perhaps a relative or member of the Vetulicolia.