Search results for "LYN"
showing 10 items of 910 documents
Pleistocene paleoenvironmental reconstructions and mammalian evolution in South-East Asia: focus on fossil faunas from Thailand.
2006
16 pages; International audience; Mammalian faunal studies have provided various clues for a better reconstruction of hominid Quaternary paleoenvironments. Inthis work, two methods were used: (1) the cenogram method, based on a graphical representation of the mammalian communitystructure, and (2) the species richness of murine rodents to estimate climatic parameters. These methods were applied to Middle andLate Pleistocene mammalian faunas of South-East Asia, from South China to Indonesia. Special emphasis was laid on a fauna fromnorth-east Thailand dated back to approximately 170,000 years (i.e. a glacial period). This Thai fauna seems characteristic of aslightly open forested environment …
Palynofacies and calcareous nannofossils in the Upper Kimmeridgian, southeastern Paris basin (France)
2005
AbstractThe Upper Kimmeridgian Members “Calcaires blancs supérieurs” and the “Marnes à exogyres supérieures” of the southeastern Paris basin were investigated for their palynofacies and calcareous nannofossils. These members display alternating limestone-marl lithotypes and represent shallow marine palaeoenvironments. The lower carbonate member is interpreted as a proximal palaeoenvironment (palaeobathymetry = 5 to 10 m), where storm and swell deposits were prevalent and the salinity was occasionally weak. The relative richness of brown phytoclasts in this part is favoured by good preservation related to restricted conditions. These conditions would explain the dominance of the nannofoss…
Occurrence of organic-matter-rich beds in Early Cretaceous coastal evaporitic setting (Dorset, UK): a link to long-term palaeoclimate changes?
2009
11 pages; International audience; In Dorset (southern U.K.), the Durlston Bay and Lulworth Cove sections expose lowermost Cretaceous coastal marine and non-marine partly evaporitic sediments (the so-called Purbeckian facies). An interval with organic matter (OM)-rich layers is recognized in both sections. This OM-rich interval is 20 m thick in the middle of the Durlston Bay section. Within these beds, a large OM accumulation is recorded, with total organic carbon (TOC) of up to 8.5 wt%. High hydrogen index (HI) values (up to 956 mgHC/gTOC) point to a Type I OM, generally considered as derived from algal-bacterial biomass. This contrasts with the OM present in the underlying and overlying in…
Étude paléobotanique d’une lentille argileuse cénomanienne de la carrière de Hucheloup, Maine-et-Loire, NO France : implications taxonomiques, strati…
2017
International audience; A Cenomanian clay lens in Hucheloup Quarry (Maine-et-Loire, north-western France) has yielded 82 foliar compressions and impressions, of which 62 were identified at several taxonomic levels. The plants are ascribed to diverse Pinales (27%), ferns (27%), Ginkgoales (26%), angiosperms (19%) and Cycadales (1%). The most abundant species in the assemblage are Frenelopsis alata (K. Feistmantel) E. Knobloch emend. J. Kvaček (Pinales) and Eretmophyllum obtusum (Velenovský) J. Kvaček (syn. E. andegavense Pons, Bourreau et Broutin) (Ginkgoales). Wood fragments, along with very well-preserved cuticles, have also been recovered and identified. The specimens are usually very fra…
Le site à ambre et plantes du Cénomanien de Neau (Mayenne, France)
2020
International audience; A new Cenomanian amber- and plant-bearing deposit has been discovered at Neau, in the Mayenne department (France). The Cenomanian fossiliferous lignites are located in karst filling in a substratum of Cambrian limestones. The amber corresponds mainly to tiny millimetric grains, devoid of arthropod inclusions, but rich in microorganisms, especially the sheated bacteria Leptotrichites resinatus , and containing pollen grains ( Classopollis ) and wood fibers (Araucariacae or Cheirolepidiaceae). The lignites provide abundant conifer and ginkgoale cuticle fragments ( Frenelopsis , Eretmophyllum ) and a lot of palynomorphs ( e.g. Gleicheniidites senonicu s, Cyathidites , D…
Spatio-temporal dynamics of genetic variation in the Iberian lynx along its path to extinction reconstructed with ancient DNA
2017
here is the tendency to assume that endangered species have been both genetically and demographically healthier in the past, so that any genetic erosion observed today was caused by their recent decline. The Iberian lynx (Lynx pardinus) suffered a dramatic and continuous decline during the 20th century, and now shows extremely low genome- and species-wide genetic diversity among other signs of genomic erosion. We analyze ancient (N = 10), historical (N = 245), and contemporary (N = 172) samples with microsatellite and mitogenome data to reconstruct the species' demography and investigate patterns of genetic variation across space and time. Iberian lynx populations transitioned from low but …
A Tale of Big Game and Small Bugs
1999
Animal populations undergo repetitive cycles of rising and falling numbers. In a Perspective, [Ranta and colleagues][1] discuss the value of time-series analyses for examining the changing dynamics of animal populations. A large time series gathered by the Hudson Bay Company based on the fur trade has provided invaluable data on the rise and fall of the Canadian lynx population from 1821 to the present. Analysis of this time series reveals that climate as well as factors influencing birth and death rates are important in regulating the lynx population ([ Stenseth et al .][2]). In a separate study, mathematical modeling combined with fieldwork revealed the importance of predators in determin…
The Eurasian Modern Pollen Database (EMPD), version 2
2020
The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60% from 4826 to…
Dispersal and colonization in heterosporous lycophytes: palynological and biogeographical notes on the genus Isoetes in the Mediterranean region
2016
After a short review of the available information on dispersal in the heterosporous genus Isoetes, which has been the subject of some mainly anecdotal or occasional observations, a case study in the Mediterranean area is presented. In the geographical context given by the island of Sicily with its satellite islets and archipelagos, the distribution of terrestrial and amphibian Isoetes species was analysed to verify if any of them occurred in the oceanic (‘thalassogenous’) islets, never connected to the mainland. The only species revealed to be able to cross the geographical and ecological barrier represented by the sea and colonize some volcanic islands was Isoetes durieui Bory, a terrestri…
Efficient estimation of generalized linear latent variable models.
2019
Generalized linear latent variable models (GLLVM) are popular tools for modeling multivariate, correlated responses. Such data are often encountered, for instance, in ecological studies, where presence-absences, counts, or biomass of interacting species are collected from a set of sites. Until very recently, the main challenge in fitting GLLVMs has been the lack of computationally efficient estimation methods. For likelihood based estimation, several closed form approximations for the marginal likelihood of GLLVMs have been proposed, but their efficient implementations have been lacking in the literature. To fill this gap, we show in this paper how to obtain computationally convenient estim…