Number and arrangement of extraocular muscles in primitive gnathostomes: Evidence from extinct placoderm fishes

Gavin C. Young

    Research output: Contribution to journalArticlepeer-review

    26 Citations (Scopus)

    Abstract

    Exceptional 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.

    Original languageEnglish
    Pages (from-to)110-114
    Number of pages5
    JournalBiology Letters
    Volume4
    Issue number1
    DOIs
    Publication statusPublished - 23 Feb 2008

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