Search results for "Universe"
showing 10 items of 2171 documents
Stratigrafía e diversidade dos vertebrados da Formação Santana.
2010
Diversification of atypical Paleozoic echinoderms: a quantitative survey of patterns of stylophoran disparity, diversity, and geography.
2006
28 pages; International audience; The analysis of morphological disparity and of morphospace occupation through the macroevolutionary history of clades is now a major research program in paleobiology, and increasingly so in organismal and comparative biology. Most studies have focused on the relationship between taxonomic diversity and morphological disparity, and on ecological or developmental controls. However, the geographic context of diversification has remained understudied. Here we address geography quantitatively. Diversity, disparity, and paleogeographic dispersion are used to describe the evolutionary history of an extinct echinoderm clade, the class Stylophora (cornutes, mitrates…
Présence de Dinosaures Théropodes, et probablement, d'Ornithopodes et de Sauropodes, dans le marais maritime du Bajocien-Bathonien des Causses.
2006
35 pages
Découverte en Bourgogne de deux ammonites sinémuriennes remarquables du genre Angulaticeras, (Schlotheimiidae). Implications taxonomiques et paléobio…
2010
Céphalopodes; Jurassique inférieur; Sinémurien; Ontogenèse; Phylogénie; Paléobiogéographie; National audience; Deux ammonites, Angulaticeras greenoughi (J. Sowerby, 1816) et A. sp. nov. aff. angustisulcatum (Geyer, 1886), récemment découvertes dans des dépôts du Sinémurien de Bourgogne, sont décrites. La seconde de ces formes correspond probablement à une espèce nouvelle. Ces deux ammonites appartiennent à la famille des Schlotheimiidae et plus particulièrement au genre Angulaticeras. La découverte de ces formes rares permet, d'abord de décrire les modalités, mal connues, de l'ontogenèse d'un très grand Schlotheimiidae du Sinémurien inférieur, ensuite d'affiner la compréhension des relation…
Éloge d'Henri Tintant (1918-2002) : l'homme et le scientifique.
2006
20 pages
Traces de pas de dinosaures du Jurassique moyen : bilan sur deux décennies de découvertes en Lozère.
2021
8 pages; National audience; Depuis 1999, des découvertes fortuites ainsi que des campagnes de prospections menées en Lozère ont livré plusieurs sites à empreintes de pas de dinosaures d’âge jurassique moyen. Le nombre, la diversité et la remarquable préservation de ces traces constituent un patrimoine paléontologique exceptionnel. Les sites principaux sont localisés dans les Gorges du Tarn et de la Jonte. Leur récente étude a révélé (1) que ces empreintes ont été laissées par des dinosaures théropodes et sauropodes (2) que les écosystèmes parcourus par ces dinosaures correspondaient à des milieux tropicaux et littoraux tels que des marais côtiers, de vastes lagunes ou des baies bordées par …
A new Griesbachian-Dienerian (Induan, Early Triassic) ammonoid fauna from Gujiao, South China.
2019
24 pages; International audience; Bed-by-bed sampling of the lower portion of the Daye Formation at Gujiao, Guizhou Province, South China, yielded new Griesbachian–Dienerian (Induan, Early Triassic) ammonoid faunas showing a new regional Induan ammonoid succession. This biostratigraphic scheme includes in chronological order the late Griesbachian Ophiceras medium and Jieshaniceras guizhouense beds, and the middle Dienerian Ambites radiatus bed. The latter is recognized for the first time as a separate biozone in South China. Eight genera and 13 species are identified, including one new species, Mullericeras gujiaoense n. sp. The new data show that a relatively high level of ammonoid taxonom…
Iron isotopes in micropyrites from the 2.7Ga Tumbiana Formation (Western Australia)
2019
International audience; Stromatolites are considered to be the major drivers for the oceanic oxygenation during Archean time. However, respective rolesof photosynthetic and chemolithotroph organisms in these Archean rocks is not precisely demonstrated. Primarysub-micrometer pyrites associated with pristine organic matter are widespreadin Archean and modern sediments. Iron isotopes are fractionated by redox processesand biological activitiesand are widely used for tracing paleoredox conditions, diagenetic processes ormetabolic signaturesas iron respiration (DIR). Sub micrometer δ56Fevalues ofmicropyritesassociated with organic matter-laminae and CaCO3-SiO2matrixin stromatolites from the 2.7G…
Late Griesbachian (early Triassic) ammonoids and nautiloids from the Dinwoody Formation at Crittenden Springs, Elko County, Nevada.
2021
International audience; We document a relatively small but very important late Griesbachian ammonoid and nautiloid assemblage from the Dinwoody Formation at Crittenden Springs, Elko County, Nevada. This discovery represents the first significant report of late Griesbachian ammonoids in the low-paleolatitudes of eastern Panthalassa, and it also signifies the first report of Wordieoceras wordiei and two co-occurring taxa outside of the Boreal Realm. This similarity in ammonoid faunas, irrespective of paleolatitude, provides support for the concept of weak latitudinal diversity gradients following the end-Permian extinction. The finding is even more noteworthy given the Dinwoody Formation’s re…
Molecular preservation of organic microfossils in Paleoarchean cherts
2019
International audience; Fossilization processesandthe increase of temperature and pressure conditions associated withburialinevitably alter the original biochemical signatures of organic molecules.At a certain stage, biogenic and abiotic organic structures may become undistinguishable [1].Cherts (i.e.silica-rich rocks)are well known forthe morphologicalpreservationof fossilized microorganisms.Recently,spatially resolvedinvestigations usingsynchrotron-based XANESmicrospectroscopyrevealedthatmolecular information about the organic precursor of3.4 Gamicrofossils, was preservedintheStrelley Pool chert(Pilbara, Western Australia),despite a metamorphichistory so far believed to be incompatible wi…