title: An exceptionally preserved Late Devonian actinopterygian provides a new model for primitive cranial anatomy in ray-finned fishes.
abstract: Actinopterygians (ray-finned fishes) are the most diverse living osteichthyan (bony vertebrate) group, with a rich fossil record. However, details of their earliest history during the middle Palaeozoic (Devonian) 'Age of Fishes' remains sketchy. This stems from an uneven understanding of anatomy in early actinopterygians, with a few well-known species dominating perceptions of primitive conditions. Here we present an exceptionally preserved ray-finned fish from the Late Devonian (Middle Frasnian, ca 373 Ma) of Pas-de-Calais, northern France. This new genus is represented by a single, three-dimensionally preserved skull. CT scanning reveals the presence of an almost complete braincase along with near-fully articulated mandibular, hyoid and gill arches. The neurocranium differs from the coeval Mimipiscis in displaying a short aortic canal with a distinct posterior notch, long grooves for the lateral dorsal aortae, large vestibular fontanelles and a broad postorbital process. Identification of similar but previously unrecognized features in other Devonian actinopterygians suggests that aspects of braincase anatomy in Mimipiscis are apomorphic, questioning its ubiquity as stand-in for generalized actinopterygian conditions. However, the gill skeleton of the new form broadly corresponds to that of Mimipiscis, and adds to an emerging picture of primitive branchial architecture in crown gnathostomes. The new genus is recovered in a polytomy with Mimiidae and a subset of Devonian and stratigraphically younger actinopterygians, with no support found for a monophyletic grouping of Moythomasia with Mimiidae.
authors.affiliation: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK sam.giles@earth.ox.ac.uk.
authors.forename: Sam
authors.initials: S
authors.lastname: Giles
authors.affiliation: 313 Rue Nationale, Appt. 96, Nœux-les-Mines 62290, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Darras
authors.affiliation: Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements (CR2P, UMR 7207), Sorbonne Universités, MNHN, CNRS, UPMC-Paris 6, Muséum National d'Histoire Naturelle, CP 38, 57 Rue Cuvier, 75231 Paris cedex 05, France.
authors.forename: Gaël
authors.initials: G
authors.lastname: Clément
authors.affiliation: Université de Lille-Sciences et technologies, UFR Sciences de la Terre, UMR 8198 'EvoEcoPaleo' du CNRS, Villeneuve d'Ascq cedex 59655, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Blieck
authors.affiliation: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
authors.forename: Matt
authors.initials: M
authors.lastname: Friedman
mesh_terms: D000818:Animals; D005399:Fishes / Q000033:anatomy & histology*; D005580:Fossils / Q000033:anatomy & histology*; D005602:France; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology*
keywords: Actinopterygii; Frasnian; Osteichthyes; braincase; computed tomography; gill skeleton