Sunday, 11 October 2015

Raynerius splendens: A Ray-finned Fish from the Late Devonian of Pas-de-Calais, France.

Ray-finned Fish, Actinopterygii, today comprise more than half of all living vertebrate species, but their origins are somewhat obscure. Less than 20 species have been described from the Devonian and none from any earlier deposits, and most of these Devonian Fish are described from external moulds only, with the only two known species with good internal preservation described from acid-prepared material the Gogo Formation of Australia over 30 years ago.

In a paper published in the Proceedings of the Royal Society Series B:Biological Sciences on 30 September 2015, Sam Giles of the Department ofEarth Sciences at the University of Oxford, Laurent Darras of Noeux-les-Mines, Gaël Clément of the Centre de Recherches sur la Paléobiodiversitéet les Paléoenvironnements at Sorbonne Universités, Alain Blieck ofLille University of Science and Technology and Matt Friedman, also of the Department of Earth Sciences at the University of Oxford, describe a new species of Ray-finned Fish from the Late Devonian Ferques Formation of Pas-de-Calais, France.

The specimen comprises an almost complete articulated skull within a block of matrix material. Unlike the Gogo Formation material this was not extracted with acid-preparation, but rather left within the block and accessed by micro-computed tomography, with the hope that this could preserve features of the material that might be lost to acid-preparation.

The specimen is described as Raynerius splendens, where 'Raynerius' honours the late Dorothy Rayner for her work on the Fish of the Gogo Formation, and 'splendens' means 'splendid', a reference to the excellent preservation seen in the specimen.

Raynerius splendens. (a) Rendering and (b) interpretive drawing of specimen in left lateral view. (c) Rendering and (d ) interpretive drawing of specimen in ventral view; skeletal elements interior to the dermal bones (i.e. braincase, gill skeleton) shown in grey. Abbreviations: a.on, aortic notch; av, accessory vomer; bb, basibranchial; cb, ceratobranchial; chy, ceratohyal; clav, clavicle; clm, cleithrum; cor, coronoid; dent, dentary; dhy, dermohyal; epi, epibranchial; exsc, extrascapular; fr, frontal; gul, gular; hb, hypobranchial; hh, hypohyal; hmd, hyomandibula; hmf, hyomandibular facet; ios, interorbital septum; jug, jugal; l.gul, lateral gular; m.clav, median clavicle; m.gul, median gular; mx, maxilla; na, nasal; op, operculum; pa, parietal; por, postorbital process; prscl, presupracleithrum; psp, parasphenoid; quj, quadratojugal;, branchiostegal ray; scl, supracleithrum; scl.r, sclerotic ring. Colour coding of the skeleton: blue, cheek and jaw; purple, skull roof and sclerotic ossicle; pink, braincase; dark green, hyomandibula; light green, operculogular system; turquoise, shoulder girdle; yellow, gill skeleton. Giles et al. (2015).

See also... xiphoidea: A streamlined Galeaspid Fish from the Early Devonian of Yunnan Province.                                       Galeaspid Fish were jawless Bony Fish distinguished by their heavily armoured head-shields with a median opening which apparently served as a water intake and nostril, as was as complex patterns of sensory...

The deepest evolutionary split in the jawed vertebrates (Gnathostomes) is that between the Sharks (Chondrichthyes) and Bony Fish (Osteichthyes), with all terrestrial vertebrates forming a subgroup within the...

Palaeontologists have been interested in the endocasts of vertebrate skulls (moulds of the interior of the skull made by sediment) since at least the nineteenth century, due to the possibility that these can...

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