190 research outputs found

    Eocene metatherians from Anatolia illuminate the assembly of an island fauna during Deep Time

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    Island biotas have disproportionately influenced the history and development of evolutionary biology, but understanding their genesis and evolution across geological timescales has been hindered by a poor fossil record. Here we augment the insular Eocene (~43 Ma) mammalian fauna known from the Pontide terrane of central Anatolia by describing two new metatherian taxa (stem marsupials) from the Luš lušk Member of the UzuncžarĆŸÄ±dere Formation in the Orhaniye Basin. Geological and paleontological data indicate that the Pontide terrane was an island on the northern margin of Neotethys during the middle Eocene. Reflecting its geodynamic context in a region of active tectonic convergence, the Eocene Pontide terrane hosted a unique combination of Laurasian and Gondwanan mammals, including an anachronistic radiation of pleuraspidotheriids (archaic ungulates) that went extinct on the European mainland ~13 Ma earlier. Most of the mammalian clades occupying the Pontide terrane colonized it by dispersal across marine barriers rather than being stranded there through vicariance. Endemic radiations of pleuraspidotheriid ungulates and polydolopimorphian metatherians on the Pontide terrane reveal that in situ diversification was an important factor contributing to faunal assembly and evolution. The insular fauna that arose on the Pontide terrane is highly analogous to that of modern Sulawesi, which evolved under strikingly similar geological conditions. Illustrating the ephemeral nature of insular biotas across macroevolutionary timescales, the demise of the Pontide fauna coincided with paleogeographic changes enabling more cosmopolitan taxa to reach it for the first time. The high level of endemism shown by the mammalian fauna of the UzuncžarĆŸÄ±dere Formation eliminates the Pontide terrane as a potential early Eocene dispersal corridor between western Europe and India.INSU-2011 CT49215-12W296-13EAR- 154368

    Plant-dominated assemblage and invertebrates from the lower Cenomanian of Jaunay-Clan, western France

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    International audienceTwo fossil localities are reported on the "LGV SEA" railroad from the Lower Cenomanianof Jaunay-Clan (JC), near Poitiers, western France. The laminated mudstones yielded plantfossils including ferns (Cladophlebis, Osmundophyllum, Ruffordia goeppertii, Sphenopteris),conifers (Brachyphyllum, Dammarophyllum, Pagiophyllum), and terrestrial and aquaticfreshwater angiosperms (Eucalyptolaurus depreii, Ploufolia). They are associated with acoleopteran insect that shows systematic affinities to the modern subfamily Chrysomeli-nae (Chrysomelidae). This assemblage suggests connections with arborescent vegetationgrowing in calm freshwater environment. Brackish to marine invertebrates also occurand include a dakoticancroid crab (Brachyura, Podotremata, Dakoticancroidea) and a fewbivalves (Brachidontes). They suggest brackish episodes during pond sedimentation in acoastal environment. Lastly, vertebrates are represented by an isolated feather

    Paleodrainage, paleoenvironments and paleoclimate of the Burmese Eocene series : implications on the origin and the early evolution of Asian anthropoids

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    Les plus anciens anthropoĂŻdes fossiles sont issus de plusieurs formations gĂ©ologiques asiatiques de l'EocĂšne moyen Ă  tardif (47 Ă  34 millions d'annĂ©es), parmi lesquelles la formation de Pondaung (Birmanie) a dĂ©livrĂ© la faune la plus diverse. L'objectif de cette thĂšse est de reconstituer la palĂ©ogĂ©ographie, l'environnement et le climat de l'EocĂšne birman afin de mieux comprendre leur histoire Ă©volutive. Dans un premier temps, l'Ă©volution de la provenance du sĂ©diment de Birmanie centrale a Ă©tĂ© Ă©tudiĂ©e par une approche alliant pĂ©trographie, lithostratigraphie et gĂ©ochimie isotopique. L'Ă©tude montre que la Birmanie centrale est restĂ©e Ă  l'Ă©cart de tout apport sĂ©dimentaire himalayen et tibĂ©tain et formait, Ă  l'EocĂšne, une bande cĂŽtiĂšre connectant l'avant-pays indien avec la rĂ©gion de la Sonde. Les palĂ©oenvironnements de la formation de Pondaung ont ensuite Ă©tĂ© reconstituĂ©s par une approche combinant sĂ©dimentologie fluviale, pĂ©dologie et palĂ©obotanique. Ces approches rĂ©vĂšlent un paysage de marĂ©cages saisonniers, de forĂȘts ripariennes et d'espaces ouverts, dĂ©veloppĂ©s sous un climat tropical Ă  forte saisonnalitĂ©. Les bois fossiles identifiĂ©s reprĂ©sentent diffĂ©rents Ă©cotones forestiers similaires Ă  ceux des forĂȘts de mousson actuelles. L'Ă©tude en isotope stable de gastĂ©ropodes fossiles et de dents de mammifĂšres confirme un rĂ©gime de prĂ©cipitation semblable Ă  la mousson moderne. Les palĂ©oenvironnements de Pondaung contrastent avec l'idĂ©e d'Ă©paisses forĂȘts primaires comme habitat prĂ©fĂ©rentiel des premiers anthropoĂŻdes et lient leur biodiversitĂ© aux zones tropicales saisonniĂšres, oĂč les plus grosses espĂšces, comme les amphipithĂ©cidĂ©s, Ă©taient particuliĂšrement compĂ©titives.The fossil record of the first anthropoids is currently fed by several Middle to Late Eocene Asian strata (47 to 34 millions years ago), of which the Pondaung Formation in Myanmar has yielded the most diverse and prolific fauna. The aim of this PhD is to reconstruct the paleogeography, paleoenvironments, and paleoclimate of the Eocene Burmese successions in order to better constrain the early evolutionary history of the anthropoids. The sediment provenance of central Myanmar was first studied using a multi-proxy approach, combining petrography, sedimentology and isotope geochemistry. Results show that central Myanmar was isolated from any Himalayan or Tibetan input and additionally formed a narrow coastal band linking the Indian foreland with the Sunda area during the Eocene. Alluvial palaeoenvironments of the Pondaung Formation were then reconstructed through a combined sedimentological, pedological and paleobotanical approach. Results revealed a mosaic landscape with seasonal swamps, riparian forests, and open areas, expanding under a tropical climate with significant seasonality. Fossil woods form different ecotones similar to those of modern days monsoonal forests. Paleoclimate reconstruction through stable isotope geochemistry on mammalian fossil teeth and fossil gastropods confirms a monsoonal, modern-like rainfall regime in the Eocene. Pondaung paleoenvironments contrast with the idea of Eocene evergreen rainforests as a preferential living environment for the first anthropoids and link the Eocene biodiversity of anthropoid fauna to the tropical seasonal areas, where the biggest species, such as the amphipithecids, were particularly competitive

    The Ayeyarwady River

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    The Oldest Paleo-Sal Forest ? Reconstruction of Myanmar Eocene vegetation

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    International audienceLes formations gĂ©ologiques mio-pliocĂšnes de Birmanie ont livrĂ© de nombreux restes vĂ©gĂ©taux qui permettent aujourd’hui une bonne reconstitution de la diversitĂ© ligneuse de cette pĂ©riode. Bien qu’abondants les dĂ©pĂŽts plus anciens n’ont pour l’instant fait l’objet que de peu d’études palĂ©obotaniques. Depuis une dizaine d’annĂ©es de trĂšs nombreux Ă©chantillons de bois fossiles ont pu ĂȘtre rĂ©coltĂ©s dans le cadre de plusieurs missions palĂ©ontologiques franco-birmanes. L’étude et la description d’une quarantaine de ces restes provenant de diffĂ©rents sites appartenant Ă  la Formation Pondaung nous permettent aujourd’hui de proposer une reconstitution de l’environnement forestier pour l’EocĂšne moyen. Ainsi, les Ă©chantillons de bois fossile ont Ă©tĂ© rattachĂ©s Ă  des familles botaniques modernes : Caesalpinaceae, Moraceae, Combretaceae, Sapindaceae, Malvaceae, Dipterocarpaceae, Theaceae et 5 nouvelles espĂšces ont pu ĂȘtre dĂ©crites. Les bois fossiles dĂ©crits ont Ă©tĂ© rapprochĂ©s d’espĂšces actuelles. Ces derniĂšres composent aujourd’hui diffĂ©rents Ă©cotones des forĂȘts de Sal Sud-Est asiatiques modernes, reflĂ©tant ainsi un climat probablement plus sec que ce qui avait Ă©tĂ© envisagĂ© par le passĂ©. En complĂ©ment de cette approche floristique une Ă©tude statistique des caractĂšres anatomiques du bois telle que proposĂ©e par Wiemann et al. (1998) nous permet de proposer une reconstitution de certains paramĂštres climatiques

    The Oldest Paleo-Sal Forest ? Reconstruction of Myanmar Eocene vegetation

    No full text
    International audienceLes formations gĂ©ologiques mio-pliocĂšnes de Birmanie ont livrĂ© de nombreux restes vĂ©gĂ©taux qui permettent aujourd’hui une bonne reconstitution de la diversitĂ© ligneuse de cette pĂ©riode. Bien qu’abondants les dĂ©pĂŽts plus anciens n’ont pour l’instant fait l’objet que de peu d’études palĂ©obotaniques. Depuis une dizaine d’annĂ©es de trĂšs nombreux Ă©chantillons de bois fossiles ont pu ĂȘtre rĂ©coltĂ©s dans le cadre de plusieurs missions palĂ©ontologiques franco-birmanes. L’étude et la description d’une quarantaine de ces restes provenant de diffĂ©rents sites appartenant Ă  la Formation Pondaung nous permettent aujourd’hui de proposer une reconstitution de l’environnement forestier pour l’EocĂšne moyen. Ainsi, les Ă©chantillons de bois fossile ont Ă©tĂ© rattachĂ©s Ă  des familles botaniques modernes : Caesalpinaceae, Moraceae, Combretaceae, Sapindaceae, Malvaceae, Dipterocarpaceae, Theaceae et 5 nouvelles espĂšces ont pu ĂȘtre dĂ©crites. Les bois fossiles dĂ©crits ont Ă©tĂ© rapprochĂ©s d’espĂšces actuelles. Ces derniĂšres composent aujourd’hui diffĂ©rents Ă©cotones des forĂȘts de Sal Sud-Est asiatiques modernes, reflĂ©tant ainsi un climat probablement plus sec que ce qui avait Ă©tĂ© envisagĂ© par le passĂ©. En complĂ©ment de cette approche floristique une Ă©tude statistique des caractĂšres anatomiques du bois telle que proposĂ©e par Wiemann et al. (1998) nous permet de proposer une reconstitution de certains paramĂštres climatiques
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