title: Fossil musculature of the most primitive jawed vertebrates.
abstract: The transition from jawless to jawed vertebrates (gnathostomes) resulted in the reconfiguration of the muscles and skeleton of the head, including the creation of a separate shoulder girdle with distinct neck muscles. We describe here the only known examples of preserved musculature from placoderms (extinct armored fishes), the phylogenetically most basal jawed vertebrates. Placoderms possess a regionalized muscular anatomy that differs radically from the musculature of extant sharks, which is often viewed as primitive for gnathostomes. The placoderm data suggest that neck musculature evolved together with a dermal joint between skull and shoulder girdle, not as part of a broadly flexible neck as in sharks, and that transverse abdominal muscles are an innovation of gnathostomes rather than of tetrapods.
authors.affiliation: Western Australian Organic and Isotope Geochemistry Centre, Department of Chemistry, Curtin University, Perth, Western Australia 6102, Australia.
authors.forename: Kate
authors.initials: K
authors.lastname: Trinajstic
authors.forename: Sophie
authors.initials: S
authors.lastname: Sanchez
authors.forename: Vincent
authors.initials: V
authors.lastname: Dupret
authors.forename: Paul
authors.initials: P
authors.lastname: Tafforeau
authors.forename: John
authors.initials: J
authors.lastname: Long
authors.forename: Gavin
authors.initials: G
authors.lastname: Young
authors.forename: Tim
authors.initials: T
authors.lastname: Senden
authors.forename: Catherine
authors.initials: C
authors.lastname: Boisvert
authors.forename: Nicola
authors.initials: N
authors.lastname: Power
authors.forename: Per Erik
authors.initials: PE
authors.lastname: Ahlberg
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005399:Fishes / Q000033:anatomy & histology* / Q000145:classification / Q000235:genetics*; D005580:Fossils; D008445:Maxillofacial Development / Q000235:genetics*; D009334:Neck Muscles / Q000033:anatomy & histology*; D010802:Phylogeny