- La Voulte-sur-Rhone
The late mid-Jurassic
lagerstätte at La Voûlte-sur-Rhone, in theArdèche region of southwesternFrance , offers paleontologists an outstanding view of an undisturbed paleoecosystem that was preserved in fine detail as organisms died at the site and settled to the bottom of a shallowepicontinental sea , with a folded floor that in places exceeded 200 m at this site. The site preserves a marine system of the Lower Callovian stage, a little over 160 mya. Some soft parts of organisms are preserved as phosphatised concretions, in exceptional cases down to cellular details. [ [http://palaeo.gly.bris.ac.uk/Palaeofiles/Lagerstatten/lavoulte/index.html (Department of Earth Sciences at University of Bristol): Sarah Joomun, "La Voûlte-sur-Rhone"] ; Etter 2002 notes some retinal structures in the eyes of conchilyocaridi crustacea.]The facies are exposed in a series of quarries at La Boissine, west of the village of La Voûlte-sur-Rhone. Iron pyrites in the silty shale are symptoms of an anoxic environment. The site was recognized among French paleontologists from the mid-nineteenth century for its finely detailed fossils.
At the site, well-preserved
fossil s of the firstpycnogonid s ("sea-spiders") ever found inMesozoic strata were identified in 2007. [Pycnogonids have a very patchy fossil record. S. Charbonnier, J. Vannier and B. Riou, "Jurassic sea spiders from the La Voulte-sur-Rhône Lagerstätte" "Proceedings of the Royal Society of London" B 274, reported in "Geophysical Research Abstracts" 10 (2008) ( [http://www.cosis.net/abstracts/EGU2008/02378/EGU2008-A-02378.pdf?PHPSESSID= on-line abstract] ).] The oldest Coleoid cephalopods (squid and octopus [A single specimen of a small octopus, the oldest such fossil, was published in 1982 (Etter 2002).] ) were found here. Fish,crustacean s, andbivalve s, which lived in mid-water levels and drifted down after they died,ophiuroid s [Most commonly "Ophiopinna elegans" (Etter 2002).] and burrowing worms are all to be found. Periodic turbidity flows may have washedallochthonous organisms in from a more highly oxygenated benthic fauna. Turbidity flows and the presence of two specimens of plants suggest that a shoreline was not far distant, represented today by France'sMassif Central (Etter 2002).References
*Walter Etter, "La Voulte-sur-Rhone: exquisite cephalopod preservation", in David J. Bottjer, Walter Etter, "Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life" (Columbia University Press) 2002. Full description and bibliography of the site.
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