Chordate of the three subdivisions of chordates, all have distinct skulls. They include the hagfish, which have no vertebrae. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or possibly all deuterostomes, are by their tails". Most craniates are vertebrates, in which the notochord is replaced by the vertebral column. These consist of a series of bony or cartilaginous cylindrical vertebrae, generally with neural arches that protect the spinal cord, and with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, and are therefore not regarded as vertebrates, but as members of
Political Animals and Animal Politics that if animals are excluded from basic justice, as John Rawls held, they can be defended on metaphysical grounds (what Rawls refers to as on the basis of "comprehensive doctrines", as opposed to the "public reasons" which must be used for arguments in the political realm). This is potentially liberating for animal advocates. Nonetheless, Flanders argues, animal issues may be matters of basic justice insofar as they affect humans or that animals themselves have rights. Alternatively, the wrongness of animal cruelty may be a "fixed point" in our political reasoning. Flanders concludes that Rawlsianism provides a good starting point for