Fig. 3

Developmental origins of Palaeospondylus cranial skeleton. a,b Diagrammatic anatomy of the cranial skeleton in dorsal (a) and ventral (b) views. c Cyclostome pattern in embryonic development of lamprey, hagfish, and also of Palaeospondylus. d Hypothetical developmental configuration of Palaeospondylus derived from the cyclostome craniofacial pattern. anp, anterior nasal process and its derivatives; ma, mandibular arch; mo, mouth; ne, nasal epithelium; nhp, nasohypophyseal plate; ph, pharynx; php, post-hypophyseal process and its derivatives; vert, vertebra. For other abbreviations, see Fig. 2