Clément Jauvion

Sorbonne Université

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Sylvain Bernard

Institut de minéralogie, de physique des matériaux et de cosmochimie

Sylvain Charbonnier

Structure et Instabilité des Génomes

Pierre Guériau

University of Lausanne

Ninon Robin

Centre National de la Recherche Scientifique

Carolin Haug

Ludwig-Maximilians-Universität München

Joachim T. Haug

Ludwig-Maximilians-Universität München

Denis Audo

Muséum national d'Histoire naturelle

Sylvain Pont

Institut de minéralogie, de physique des matériaux et de cosmochimie

Cristian Mocuta

Synchrotron soleil

Sylvain Charbonnier

Muséum national d'Histoire naturelle

Cooperative Institutions

Centre National de la Recherche Scientifique

Sorbonne Université

Institut de minéralogie, de physique des matériaux et de cosmochimie

Institut de Recherche pour le Développement

Muséum national d'Histoire naturelle

Institute of Paleoprimatology Human Paleontology Evolution and Paleoenvironments

Structure et Instabilité des Génomes

University of Florida

Université Claude Bernard Lyon 1

Laboratoire de Géologie de Lyon : Terre, Planètes et Environnement

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De la vie à la pierre : préservation exceptionnelle d'arthropodes marins fossiles

Clément Jauvion

Le registre fossile est incomplet et ne rend pas reellement compte de la biodiversite ancienne. Certains gisements a preservation exceptionnelle sont riches en organismes « mous » rarement fossilises. La tomographie a rayons X a revele des structures biologiques remarquables (oeufs, organes internes) nous permettant, par exemple, de reconstituer des traits reproductifs chez les Polychelida (Decapoda) du site jurassique de La Voulte-sur-Rhone. Les causes d’une telle preservation restant mal connues, les analyses in situ de la composition mineralogique d’arthropodes fossiles nous ont permis de reconstituer les processus de fossilisation au sein du meme site et d’un site cretace du Liban. Nous montrons ainsi que la biodegradation est primordiale dans la fossilisation, et que le mode de preservation s’explique par la precipitation autour du fossile d’une concretion (fossiles en volume) ou non (fossiles plats). Nous discutons de l’effet des microenvironnements et des microorganismes associes.

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The oldest shipworms (Bivalvia, Pholadoidea, Teredinidae) preserved with soft parts (western France): insights into the fossil record and evolution of Pholadoidea

Palaeontology (2018)

Ninon Robin Marcel Velásquez Anaïs Boura Géraldine Garcia Clément Jauvion

Abstract Teredinidae are obligate xylophagous bivalves that colonize drift wood. They display a highly derived anatomy with a reduced shell; most of their body consists of soft tissues. Consequently, fossil teredinids mostly correspond to burrows, shells or small terminal aragonite structures called ‘pallets’. We report, from mid‐Cretaceous logs of the Envigne Valley, France, exceptionally preserved wood‐boring bivalves with silicified soft parts. After characterizing the wood, we report both the molluscs’ anatomy and their distribution inside the wood (using computed tomography). The 3D‐reconstructions reveal rarely preserved soft tissues (mantle, respiratory siphons, visceral pouch) but surprisingly no mineralized pallets. Envigne shipworms display neat dorsal condyles and a vermiform body plan, making them the oldest known Teredinidae. To document the evolutionary or taphonomic origin of this lack of pallet, the mineralization of these bivalves was investigated, and it is concluded that pallets could have dissolved prior to other carbonate components. From a survey of the fossil wood‐boring bivalves and their characters, we provide a time scaled origin of the main pholadoid clades supported in recent phylogenies. Since we found no correlation between the presence of pallets in Pholadoidea and their occurrence in the stratigraphic record, we suggest that their absence during the Mesozoic could be the result of a taphonomic bias related to the ‘calcite vs aragonite seas’ paradigm. The Cenomanian Envigne Valley was an estuarine to intertidal environment in which the Teredinidae appear to have selected their wood habitat on the basis of size but not type.

Taphonomy

Cenomanian

Fossil Record

10.1111/pala.12376

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Citations (21)

Impact des processus de fossilisation : étude des crustacés exceptionnellement préservés du Jurassique de La Voulte-sur-Rhône

HAL (Le Centre pour la Communication Scientifique Directe) (2018)

Clément Jauvion Sylvain Bernard Pierre Guériau Sylvain Charbonnier

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Muscles and muscle scars in fossil malacostracan crustaceans

Earth-Science Reviews (2019)

Adiël A. Klompmaker Matúš Hyžný Roger W. Portell Clément Jauvion Sylvain Charbonnier

10.1016/j.earscirev.2019.04.012

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Exceptional preservation requires fast biodegradation: thylacocephalan specimens from La Voulte‐sur‐Rhône (Callovian, Jurassic, France)

Palaeontology (2019)

Clément Jauvion Sylvain Bernard Pierre Guériau Cristian Mocuta Sylvain Pont

Abstract Konservat‐Lagerstätten are seen as snapshots of past biodiversity for a given location and time. However, processes leading to the exceptional morphological preservation of fossils in these deposits remain incompletely understood. This results in a deficient assessment of taphonomic biases and limits the robustness/relevance of palaeobiological reconstructions. Here, we report the mineralogical characterization of crustacean fossils preserved within carbonate‐rich concretions from the Jurassic Konservat‐Lagerstätte of La Voulte‐sur‐Rhône (Ardèche, France). The combination of SEM ‐ EDS , TEM , synchrotron‐based XRF , XRD and XANES allows the mineralogical phases composing these fossils (i.e. fluorapatite, Fe‐sulfides (pyrite, pyrrhotite) and Mg‐calcite) and the surrounding matrix (i.e. Mg‐calcite, clays and detrital silicates) to be identified. Fluorapatite and pyrite (and pyrrhotite) precipitated during decay under anoxic conditions, replacing delicate organic structures and preserving anatomical details. These mineral structures were subsequently consolidated by a Mg‐calcite cement. Of note, histologically similar tissues were replaced by the same mineral phases, confirming that fossilization (in La Voulte) occurred rapidly enough to be influenced by tissue composition. Altogether, the present study shows that exceptional preservation requires fast biodegradation, thereby confirming recent experimental evidence.

Taphonomy

Lagerstätte

Fluorapatite

Authigenic

10.1111/pala.12456

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Show me your yttrium, and I will tell you who you are: implications for fossil imaging

Palaeontology (2018)

Pierre Guériau Clément Jauvion Cristian Mocuta

Abstract The development of X‐ray tomography in the last decade has led to a revolution in palaeontology by providing a means of imaging 3D fossils. In turn, imaging of flat fossils has strongly benefitted from critical improvement of synchrotron X‐ray fluorescence ( XRF ). The latter, which allows the mapping of 2D distributions of major‐to‐trace elements over decimetre‐scale objects, usually targets metals with atomic number (Z) up to strontium (K‐shell emission lines); in the same energy domain, L‐shell emission lines of heavier elements (particularly lead) can also be analysed. A fluorescence signal from strontium can escape from a depth of a few 100 μm in fossils, thereby revealing, due to its substitution for calcium in calcium phosphates (apatite group minerals and bone), hidden fossil bone or phosphatized remains. Nonetheless, strontium similarly substitutes for calcium in calcium carbonates, resulting in the absence of contrast when fossils are preserved in limestone. Here, we show that this issue can easily be overcome by using X‐rays slightly higher in energy (17.2 keV and above) to excite and detect yttrium fluorescence. Together with lanthanides (collectively known as the rare earth elements), yttrium preferentially substitutes for calcium in calcium phosphates, offering anatomical contrasts for a wider range of fossils. This is demonstrated here for three fossils (vertebrate and invertebrate) from different ages and depositional environments. We then discuss the different chemical behaviours of strontium and yttrium in calcium phosphates and carbonates. Although yttrium is also found in other (rarer) minerals, its mapping using synchrotron XRF could be used as a proxy to pinpoint calcium phosphates in fossils and other geological materials.

10.1111/pala.12377

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A mineralogist’s point of view on exceptional preservation: the case study of the La Voulte-sur-Rhône crustacean fossils

Clément Jauvion Sylvain Bernard Pierre Guériau Sylvain Charbonnier

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Palaeoecology of Voulteryon parvulus (Eucrustacea, Polychelida) from the Middle Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte (France)

Scientific Reports (2019)

Denis Audo Ninon Robin Javier Luque Michał Krobicki Joachim T. Haug

Exceptional and extremely rare preservation of soft parts, eyes, or syn-vivo associations provide crucial palaeoecological information on fossil-rich deposits. Here we present exceptionally preserved specimens of the polychelidan lobster Voulteryon parvulus, from the Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte, France, bearing eyes with hexagonal and square facets, ovaries, and a unique association with epibiont thecideoid brachiopods, giving insights onto the palaeoenvironment of this Lagerstätte. The eyes, mostly covered in hexagonal facets are interpreted as either apposition eyes (poorly adapted to low-light environment) or, less likely, as refractive or parabolic superposition eyes (compatible with dysphotic palaeoenvironments). The interpretation that V. parvulus had apposition eyes suggests an allochthonous, shallow water origin. However, the presence of thecideoid brachiopod ectosymbionts on its carapace, usually associated to dim-light paleoenvironments and/or rock crevices, suggests that V. parvulus lived in a dim-light setting. This would support the less parsimonious interpretation that V. parvulus had superposition eyes. If we accept the hypothesis that V. parvulus had apposition eyes, since the La Voulte palaeoenvironment is considered deep water and had a soft substrate, V. parvulus could have moved into the La Voulte Lagerstätte setting. If this is the case, La Voulte biota would record a combination of multiple palaeoenvironments.

Lagerstätte

Paleoecology

10.1038/s41598-019-41834-6

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A new polychelidan lobster preserved with its eggs in a 165 Ma nodule

Scientific Reports (2020)

Clément Jauvion Denis Audo Sylvain Bernard Jean Vannier Allison C. Daley

Crustacean eggs are rare in the fossil record. Here we report the exquisite preservation of a fossil polychelidan embedded within an unbroken nodule from the Middle Jurassic La Voulte-sur-Rhône Lagerstätte (France) and found with hundreds of eggs attached to the pleon. This specimen belongs to a new species, Palaeopolycheles nantosueltae sp. nov. and offers unique clues to discuss the evolution of brooding behaviour in polychelidan lobsters. In contrast to their development, which now relies on a long-lived planktic larval stage that probably did not exist in the early evolutionary steps of the group, the brood size of polychelidan lobsters seems to have remained unchanged and comparatively small since the Jurassic. This finding is at odds with reproductive strategies in other lobster groups, in which a long-lived planktic larval stage is associated with a large brood size.

10.1038/s41598-020-60282-1

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After 100 years: a detailed view of an eumalacostracan crustacean from the Upper Jurassic Solnhofen Lagerstätte with raptorial appendages unique to Euarthropoda

Lethaia (2020)

Paula G. Pazinato Clément Jauvion Günter Schweigert Joachim T. Haug Carolin Haug

The Solnhofen Konservat-Lagerstätte yields a great number of remarkably preserved fossils of eumalacostracan crustaceans that help us understand the early radiation of several groups with modern representatives. One fossil from there, Francocaris grimmi Broili, 1917 is a small shrimp-like crustacean originally described about 100 years ago as a mysidacean crustacean (opossum shrimps and relatives) from latest Kimmeridgian – early Tithonian (Upper Jurassic) of the Solnhofen Lithographic Limestones of Southern Germany. New material with exceptionally preserved specimens, allied with modern imaging techniques (mostly composite fluorescence microscopy), allows us to provide a detailed re-description of this species. The most striking feature of Francocaris grimmi is an extremely elongated thoracopod 7 with its distal elements forming a spiny sub-chela. This character supports a sister group relationship of Francocaris grimmi with Eucopiidae, an ingroup of Lophogastrida, pelagic peracaridans common in marine environments throughout the world. We also discuss other supposed fossil representatives of Lophogastrida, identifying all of them as problematic at best. The structure of the sub-chela in F. grimmi indicates an original use in raptorial behaviour. Francocaris grimmi appears to be unique in possessing such a far posterior sub-chelate appendage as a major raptorial structure. In most representatives of Euarthropoda in which sub-chelate appendages occur and are used for food intake, they are usually closer to the mouth.

Appendage

Chela

Lagerstätte

Sister group

10.1111/let.12382

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Citations (8)