Citations des revues de paléontologie : bilan 2005

L'Association Paléontologique Française (APF) propose un bilan annuel des citations d'une trentaine de revues, dont une dizaine française. En voici le bilan 2005. Cet index de l'APF ne cherche pas à se substituer au facteur d'impact (FI) fourni par l'ISI, mais plutôt à fournir un document de référence fiable à l'échelle de la paléontologie. Le fait de disposer d'un index de citation interne à cette discipline apparait plus utile et plus approprié pour la hiérarchisation de ces revues disciplinaires que le FI officiel qui intègre dans une même hiérarchie des revues de disciplines diverses aux communautés hétérogènes en nombre de chercheurs, ce nombre étant corrélé avec le FI

Oldest Omaliini (Coleoptera: Staphylinidae: Omaliinae) Discovered in the Opaque Cretaceous Amber of Charentes

International audienceAppartenant aux Staphylinidae, la plus grande famille animale connue, les Omaliinae actuels constituent un groupe de scarabées très diversifié' et à large répartition mondiale. Des représentants des Omaliinae sont connus depuis le Jurassique inférieurà moyen, via des fossiles en compression, mais la tribu des Omaliini n'est identifiée qu'à partir du Cénozoïque. Duocalcar geminum Peris and Thayer gen. et sp. nov. est décrit comme le plus ancien fossile connu de cette tribu, et provient de l'ambre opaque du Crétacé moyen (Albien terminal) des Charentes (Sud-Ouest de la France). Sa découverte et sa description ont été rendues possibles grâce a' l'utilization des techniques d'imagerie RX synchrotron en contraste de phase, qui permettent une étude détaillée des inclusions d'insectes dans l'ambre opaque

Re-examination of the palynological content of the Lower Cretaceous deposits of Angeac, Charente, south-west France::Age, palaeoenvironment and taxonomic determinations

International audienceFurther to the work published by Néraudeau et al. six years ago, palynological matter recovered from the lignitic bone bed of Angeac in Charente (south-west France) has been re-examined in order to provide more evidence of its age, the previous Hauterivian–Barremian interpretation being regarded as controversial. The samples come from four sedimentological units, An2–An5, which together yielded an assemblage of 34 species, taxonomically dominated by palaeoecologically significant lygodiaceous verrucate spores, including eight species attributable to the genus Concavissimisporites and three species of Trilobosporites. A few bisaccate pollen grains, including Vitreisporites pallidus, have been recovered, but the gymnospermous pollen spectrum is clearly dominated by the cheirolepidiaceous genus Classopollis, its abundance diminishing progressively upwards from units An4 to An2. The great abundance and diversity of verrucate forms, along with the presence of other spores typical of Lower Cretaceous deposits, such as Aequitriradites verrucosus, and the scarcity of specimens referable to Cicatricosisporites, render this assemblage most similar to those of the Hastings Group of southern England, and the Bückeberg Formation in north-western Germany. The time of deposition is, therefore, more likely to have been Berriasian–Valanginian rather than Hauterivian–Barremian, as previously stated. The associated small assemblage of megaspores is consistent with this determination. Except for Trilobosporites and Concavissimisporites, the use of several other genera commonly applied to Mesozoic verrucate spores, such as Converrucosisporites and Impardecispora, is considered unnecessary. To support this assertion, a Principal Components Analysis has been carried out on 120 verrucate spores from sedimentological units An2–4, taking into account ten morphological variables. The results show that specimens attributable to Trilobosporites are well be separated from the main cluster, which corresponds to Concavissimisporites, underlining the futility of using more than two genera for the species concerned

Study of the Histology of Leafy Axes and Male Cones of Glenrosa carentonensis sp. nov. (Cenomanian Flints of Charente-Maritime, France) Using Synchrotron Microtomography Linked with Palaeoecology

International audienceWe report exceptionally well-preserved plant remains ascribed to the extinct conifer Glenrosa J. Watson et H.L. Fisher emend. V. Srinivasan inside silica-rich nodules from the Cenomanian of the Font-de-Benon quarry, Charente-Maritime, western France. Remains are preserved in three dimensions and mainly consist of fragmented leafy axes. Pollen cones of this conifer are for the first time reported and in some cases remain connected to leafy stems. Histology of Glenrosa has not previously been observed; here, most of internal tissues and cells are well-preserved and allow us to describe a new species, Glenrosa carentonensis sp. nov., using propagation phase-contrast X-ray synchrotron microtomography, a non-destructive technique. Leafy axes consist of characteristic helically arranged leaves bearing stomatal crypts. Glenrosa carentonensis sp. nov. differs from the other described species in developing a phyllotaxy 8/21, claw-shaped leaves, a thicker cuticle, a higher number of papillae and stomata per crypt. Pollen cones consist of peltate, helically arranged microsporophylls, each of them bearing 6–7 pollen sacs. The new high resolution tomographic approach tested here allows virtual palaeohistology on plants included inside a dense rock to be made. Most tissues of Glenrosa carentonensis sp. nov. are described. Lithological and palaeontological data combined with xerophytic features of Glenrosa carentonensis sp. nov. suggest that this conifer has been adapted to survive in harsh and instable environments such as coastal area exposed to hot, dry condition

Phase Contrast X-Ray Synchrotron Imaging

A significant portion of Mesozoic amber is fully opaque. Biological inclusions in such amber are invisible even after polishing, leading to potential bias in paleoecological and phylogenetic studies. Until now, studies using conventional X-ray microtomography focused on translucent or semi-opaque amber. In these cases, organisms of interest were visualized prior to X-ray analyses. It was recently demonstrated that propagation phase contrast X-ray synchrotron imaging techniques are powerful tools to access invisible inclusions in fully opaque amber. Here we describe an optimized synchrotron microradiographic protocol that allowed us to investigate efficiently and rapidly large amounts of opaque amber pieces from Charentes (southwestern France). Amber pieces were imaged with microradiography after immersion in water, which optimizes the visibility of inclusions. Determination is not accurate enough to allow precise phylogenetic studies, but provides preliminary data on biodiversity and ecotypes distribution; phase contrast microtomography remains necessary for precise determination. Because the organisms are generally much smaller than the amber pieces, we optimized local microtomography by using a continuous acquisition mode (sample moving during projection integration). As tomographic investigation of all inclusions is not practical, we suggest the use of a synchrotron for a microradiographic survey of opaque amber, coupled with microtomographic investigations of the most valuable organisms.Peer Reviewe

Citations des revues de paléontologie : bilan 2008

L'Association Paléontologique Française (APF) propose un bilan annuel des citations d'une trentaine de revues, dont une dizaine française. En voici le bilan 2008. Cet index de l'APF ne cherche pas à se substituer au facteur d'impact (FI) fourni par l'ISI, mais plutôt à fournir un document de référence fiable à l'échelle de la paléontologie. Le fait de disposer d'un index de citation interne à cette discipline apparait plus utile et plus approprié pour la hiérarchisation de ces revues disciplinaires que le FI officiel qui intègre dans une même hiérarchie des revues de disciplines diverses aux communautés hétérogènes en nombre de chercheurs, ce nombre étant corrélé avec le FI

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

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

New, primitive termites (Isoptera) from Early Cretaceous ambers of France and Lebanon

This is the publisher's version, also available electronically from palaeodiversity.org.Three new genera and species of primitive termites (Isoptera) are described and figured from Early Cretaceous French and Lebanese ambers: Santonitermes chloeae ENGEL, NEL & PERRICHOT, n. gen., n. sp., from an imago preserved in Charentese amber (Albian–Cenomanian); Syagriotermes salomeae ENGEL, NEL & PERRICHOT, n. gen., n. sp., from an alate detected in opaque amber from the same locality and reconstructed using synchrotron microtomographic imaging; and Lebanotermes veltzae ENGEL, AZAR & NEL, n. gen., n. sp., from an alate preserved in Lebanese amber (Aptian). The three genera exhibit primitive features of the Meiatermes-grade of early isopteran genera (sensu ENGEL et al. 2009). In addition, three further fragmentary specimens from Lebanon amber are reported, each apparently distinct from Lebanotermes n. gen. and the previously described Melqartitermes ENGEL et al., 2007. The new fossils further document the diversity and morphological disparity of ‘lower’ termite groups during the Early Cretaceous, highlighting the importance of palaeontological material for understanding isopteran phylogeny as well as the diversification of Isoptera in the latest Jurassic and Early Cretaceous

Upper Cretaceous amber from Vendée, north-western France:Age dating and geological, chemical, and palaeontological characteristics

International audienceThe Upper Cretaceous lignite deposits of La Garnache, Vendée (western France), consist of two lignitic clay series, Garnache 1 and Garnache 2, separated by a fault. The first series cropped out to the south of the fault during road works until 2002 but is now covered by an embankment. It has provided numerous pieces of amber containing arthropod and microorganism inclusions. The second lignitic series, exposed to the north of the fault, is rich in fossil wood but devoid of amber. Palynological analysis of Garnache 1 revealed several Normapolles species belonging to the genera Atlantopollis, Complexiopollis, Osculapollis, Plicapollis and Trudopollis, but larger forms typical of Senonian deposits are absent. By contrast, Garnache 2 proved to be dominated taxonomically and numerically by spores (Appendicisporites, Camarozonosporites, Gleicheniidites, Patellasporites, Stereisporites), associated with a few gymnosperm (Cerebropollenites, Phyllocladidites, Classopollis) and angiosperm (Liliacidites, Retitricolpites and a single specimen of the Normapolles Complexiopollis) taxa. Garnache 1 is, therefore, younger than Garnache 2, the latter being clearly Cenomanian in age whereas Garnache 1 is more likely to be Turonian. Lignitic clay of Garnache 1 contains numerous translucent, orange to red, pieces of amber. Vendean amber is rich in aquatic arthropods, such as tanaids and epicarideans (Crustacea), as well as marine or brackish siliceous microorganisms such as diatoms and sponge spicules. These aquatic inclusions indicate that resin-producing trees grew along and close to the seashore. The amber-bearing clay was deposited in a calm, estuarine or lagoonal, muddy environment

Dinosaures crétacés en Charente: résultats des fouilles de l'été 2010

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