ABSTRACT
Current phylogenies of extant and fossil craniate taxa suggest that the armoured, jawless ‘ostracoderms’ are more closely related to the gnathostomes than to either hagfishes or lampreys. These fossils show that a number of characters, which are unique to the gnathostomes among living craniates, appeared before the rise of jaws. ‘Ostracoderms’, in particular galeaspids and osteostracans, can thus provide information on the shaping of the gnathostome characters and the general gnathostome condition. This is exemplified here with the shaping of the gnathostome braincase and nasohypophysial complex.
