Search results for "PG"
showing 10 items of 1521 documents
Effect of simulated faunal impoverishment and mixture on the ecological structure of modern mammal faunas: Implications for the reconstruction of Mio…
2011
15 pages; International audience; The strong link between environment and the ecological diversity of communities is often used for drawing palaeoenvironmental inferences from fossil assemblages. Here we focus on the reliability of fossil samples in comparison to original communities when inferring palaeoenvironments from the ecological diversity of fossil mammal faunas. Taphonomic processes and sampling techniques generally introduce two kinds of biases in fossil samples: 1) the directional impoverishment of communities, i.e. the absence of some specific categories of bones, individuals or species; and 2) the mixture of several communities, temporally (timeaveraging) and/or spatially (spac…
Late Quaternary changes in bat palaeobiodiversity and palaeobiogeography under climatic and anthropogenic pressure: new insights from Marie-Galante, …
2016
25 pages; International audience; Data on Lesser Antillean Late Quaternary fossil bat assemblages remains limited, leading to their general exclusion from studies focusing on Caribbean bat palaeobiodiversity and palaeobiogeography. Additionally, the role of climatic versus human pressure driving changes in faunal communities remains poorly understood. Here we describe a fossil bat assemblage from Blanchard Cave on Marie-Galante in the Lesser Antilles, which produced numerous bat remains from a well-dated, stratified context. Our study reveals the occurrence of at least 12 bat species during the Late Pleistocene and Early Holocene on Marie-Galante, whereas only eight species are currently kn…
Middle Jurassic tracks of sauropod dinosaurs in a deep karst cave in France.
2019
14 pages; International audience; Although the deep galleries of natural underground cavities are difficult to access and are sometimes dangerous, they have the potential to preserve trace fossils. Here, we report on the first occurrence of sauropod dinosaur tracks inside a karstic cave. Three trackways are preserved on the roof of the Castelbouc cave 500 m under the surface of the Causse Méjean plateau, southern France. The tracks are Bathonian in age (ca. 168–166 Ma), a crucial but still poorly known time interval in sauropod evolution. The three trackways yield sauropod tracks that are up to 1.25 m long and are therefore amongst the largest known dinosaur footprints worldwide. The trackm…
Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study.
2016
17 pages; International audience; In biogeography, the similarity distance decay (SDD) relationship refers to the decrease in compositional similarity between communities with geographical distance. Although representing one of the most widely used relationships in biogeography, a review of the literature reveals that: (1) SDD is influenced by both spatial extent and sample size; (2) the potential effect of the phylogenetic level has yet to be tested; (3) the effect of a marked biogeographical structuring upon SDD patterns is largely unknown; and (4) the SDD relationship is usually explored with modern, mainly terrestrial organisms, whereas fossil taxa are seldom used in that perspective. U…
Biodiversity is not (and never has been) a bed of roses!
2011
9 pages; International audience; Over the last decades, the critical study of fossil diversity has led to significant advances in the knowledge of global macroevolutionary patterns of biodiversity. The deep-time history of life on Earth results from background originations and extinctions defining a steady-state, nonstationary equilibrium occasionally perturbed by biotic crises and "explosive" diversifications. More recently, a macroecological approach to the large-scale distribution of extant biodiversity offered new, stimulating perspectives on old theoretical questions and current practical problems in conservation biology. However, time and space are practically distinct, but functional…
Allometric space and allometric disparity: a developmental perspective in the macroevolutionary analysis of morphological disparity.
2008
8 pages; International audience; Here, we advance novel uses of allometric spaces--multidimensional spaces specifically defined by allometric coefficients--with the goal of investigating the focal role of development in shaping the evolution of morphological disparity. From their examination, operational measures of allometric disparity can be derived, complementing standard signals of morphological disparity through an intuitive and process-oriented refinement of established analytical protocols used in disparity studies. Allometric spaces thereby become a promising context to reveal different patterns of evolutionary developmental changes and to assess their relative prevalence and import…
Paleohistology of the Cretaceous resin‐producing conifer Geinitzia reichenbachii using X‐ray synchrotron microtomography
2021
International audience; PremiseThe conifer Geinitzia reichenbachii was a common member of the Cretaceous Laurasian floras. However, the histology of G. reichenbachii leafy axes was never described in detail, and our knowledge of its paleoecology remains very limited. Using new and exquisitely preserved silicified material from the Upper Cretaceous of western France, we describe G. reichenbachii from the gross morphology to the cellular scale, then discuss paleoecological and taphonomical implications.MethodsWe examined specimens from two localities in western France (Claix and Moragne) using propagation phase-contrast X-ray synchrotron microtomography.ResultsThe cuticle and the inner tissue…
Tendencies in paleontological practice when defining species, and consequences on biodiversity studies
2005
The exploration of evolutionary patterns over geological time has recently received new impetus from the development of morphological disparity as a new biodiversity metric alongside taxonomic diversity. Clade dynamics can be analyzed by comparing and contrasting these two metrics. Like any metrics based on sampling, quantification, and naming, taxonomic diversity and morphological disparity are not free from bias. The long use of taxonomic diversity has prompted many studies of bias and its effects, whereas bias affecting morphological disparity has only been summarily explored. This is particularly so for the effect of the growth of knowledge over paleontographical time (i.e., historical …
Conifers from the Cenomanian amber of Fouras (Charente-Maritime, western France)
2020
Fossil inclusions of arthropods and microorganisms are abundant in the Cretaceous amber from western France, but plant meso- or macroremains are scarce. Preserved remains are mostly tiny, very fragmented, and indeterminable. Only one amber locality in the Charente department has already provided conifer remains. Here, we report the first plant mesoremains ensnared in Cenomanian amber from Fouras – Bois Vert, in the Charente-Maritime department. They consist of three well-preserved leafy axes and one cone of Cheirolepidiacean conifers. Based on the helical arrangement of rhomboidal, longer than wide, and highly adpressed leaves, leafy axes are ascribed to the genus Pagiophyllum. The ovoid co…
The cranium of Proviverra typica (Mammalia, Hyaenodonta) and its impact on hyaenodont phylogeny and endocranial evolution.
2019
19 pages; International audience; We describe the first endocast reconstruction of a hyaenodont mammal based on X‐ray microtomography. The endocast belongs to the type material of the European hyaenodont Proviverra typica. We performed phylogenetic analysis to contextualize the evolution of endocranial size and complexity in Hyaenodonta. We added several European hyaenodonts and modified several codings of the most recent character–taxon matrix established to question the relationships within Hyaenodonta. Including these new species in a phylogenetic analysis reveals a new clade: Hyaenodontoidea. Comparisons with several previously described endocasts show that there was an increase in comp…