Young, Gavin2015-12-081744-9561http://hdl.handle.net/1885/33950Exceptional braincase preservation in some Devonian placoderm fishes permits interpretation of muscles and cranial nerves controlling eye movement. Placoderms are the only jawed vertebrates with anterior/posterior obliques as in the jawless lamprey, but with the same function as the superior/inferior obliques of other gnathostomes. Evidence of up to seven extraocular muscles suggests that this may be the primitive number for jawed vertebrates. Two muscles innervated by cranial nerve 6 suggest homologies with lampreys and tetrapods. If the extra muscle acquired by gnathostomes was the internal rectus, Devonian fossils show that it had a similar insertion above and behind the eyestalk in both placoderms and basal osteichthyans.Keywords: Devonian; extinction; fish; fossil; homology; muscle; abducens nerve disease; anterior oblique muscle; article; cranial nerve; extinct species; extraocular muscle; eye movement; fish; fossil; inferior oblique muscle; innervation; internal rectus muscle; l Eye muscles; Gnathostome phylogeny; Jaw evolution200810.1098/rsbl.2007.05452015-12-08