GEOSCAN, résultats de la recherche


TitreReconstructing the mouth of the first vertebrates
AuteurGoudemand, N; Orchard, M J; Urdy, S; Bucher, H; Tafforeau, P
Source34th International Geological Congress, abstracts; 2012 p. 1
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120101
Réunion34th International Geological Congress; Brisbane; AU; août 5-10, 2012
Sujetsvertébrés; paléontologie des vertébrés; morphologie des fossiles; paléontologie
Programmebassins sédimentaires du Yukon, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
The origin of jaws remains largely an enigma that is best addressed by studying fossil and living jawless vertebrates. Conodonts were marine, eel-shaped animals, whose vertebrate affinity is still disputed. The general architecture of the conodont oral skeleton is a bilaterally symmetrical array of usually 15 phosphatic elements, which generally gets disarticulated after the decay of the supporting tissues. Hence most conodonts are known only as isolated elements.
From the detailed study of hundreds of articulated 'natural assemblages' and photographic simulation of their collapse, Purnell and Donoghue (1997) reconstructed a convincing 3D model of the Idiognathodus apparatus (presumably a template for all ozarkodinid conodonts) in a single position : a putative generalized resting (dead) position.
Based on new partial natural assemblages, imaged using propagation phase-contrast X-ray synchrotron microtomography (ID19 beamline at the ESRF, Grenoble), and the new interpretation of other articulated fossils preserving uncommon configurations of the apparatus, we reconstructed the other working positions and developed a 3D animated functional model (Goudemand et al., 2011). Thereof we deduced that the skeleto-muscular mechanism used by conodonts for feeding was very similar to that of extant cyclostomes (lampreys and myxinoids). This lends additional support to the interpretation of conodonts as 'primitive' vertebrates and it suggests that the first vertebrates used a similar, pulley-like, feeding mechanism before the apparition of jaws.