Search results for "Hom"
showing 10 items of 8335 documents
Variations morphologiques des Toxaster (Echinoida : Spatangoida) en regard des fluctuations spatiales (Arc de Castellane, SE France) et temporelles (…
2006
Resume L'impact du milieu sedimentaire sur l'installation, la croissance et la morphologie de spatangues primitifs du Cretace inferieur, est analyse chez le genre Toxaster dans le Valanginien et l'Hauterivien de l'Arc de Castellane au Nord de la plate-forme provencale. Les analyses concernent la dimension spatiale a partir de l'etude comparative de six populations isochrones de Toxaster granosus kiliani de la biozone a Verrucosum distribuees le long d'un gradient proximo-distal, puis la dimension temporelle a partir de l'etude d'une coupe de reference (Carajuan) couvrant l'intervalle stratigraphique Valanginien superieur–Hauterivien superieur et concernant principalement les especes T. gran…
Vegetation dynamics of Kisima Ngeda freshwater spring reflect hydrological changes in northern Tanzania over the past 1200 years: implications for pa…
2021
13 pages; International audience; Kisima Ngeda (KN), a spring on the northern margin of saline Lake Eyasi, Tanzania, sustains an Acacia-Hyphaene palm woodland and Typha swamps, while the surrounding vegetation is semi-desert. To study the vegetation changes associated with this spring, which represents a plausible modern analog for the fossil springs documented in the nearby paleoanthropological and archaeological sites of Olduvai Gorge, we analyzed the pollen content of a 43 cm-long sediment core that documents vegetation changes since the last ~1200 years (from cal yrs. C.E. 841 to 2011). Our results show that (1) Hyphaene palms, which require meso-halophytic soil conditions were most abu…
Early evidence of fire in south-western Europe: the Acheulean site of Gruta da Aroeira (Torres Novas, Portugal)
2020
The site of Gruta da Aroeira (Torres Novas, Portugal), with evidence of human occupancy dating to ca. 400 ka (Marine Isotope Stage 11), is one of the very few Middle Pleistocene localities to have provided a fossil hominin cranium associated with Acheulean bifaces in a cave context. The multi-analytic study reported here of the by-products of burning recorded in layer X suggests the presence of anthropogenic fires at the site, among the oldest such evidence in south-western Europe. The burnt material consists of bone, charcoal and, possibly, quartzite cobbles. These finds were made in a small area of the cave and in two separate occupation horizons. Our results add to our still-limited know…
Uneven Data Quality and the Earliest Occupation of Europe—the Case of Untermassfeld (Germany)
2017
AbstractThe database regarding the earliest occupation of Europe has increased significantly in quantity and quality of data points over the last two decades, mainly through the addition of new sites as a result of long-term systematic excavations and large-scale prospections of Early and early Middle Pleistocene exposures. The site distribution pattern suggests an ephemeral presence of hominins in the south of Europe from around one million years ago, with occasional short northward expansions along the western coastal areas when temperate conditions permitted. From around 600,000-700,000 years ago Acheulean artefacts appear in Europe and somewhat later hominin presence seems to pick up, w…
Radial Symmetry, the Anterior/Posterior Axis, and Echinoderm Hox Genes
2008
20 pages; International audience; The strangeness of echinoderm pentaradiality results from superposition of radial symmetry onto ancestral deuterostome bilaterality. The Extraxial- Axial Theory shows that echinoderms also have an anterior/posterior (A/P) axis developed independently and ontogenetically before radiality. The A/P axis is first established via coelomic stacking in the extraxial region, with ensuing development of the pentamerous hydrocoel in the axial region. This is strongly correlated with a variety of gene expression patterns. The echinoid Hox cluster is disordered into two different sets of genes. During embryogenesis, members of the posterior class demonstrate temporal, …
After the emergence of the Acheulean at Melka Kunture (Upper Awash, Ethiopia): From Gombore IB (1.6 Ma) to Gombore Iγ (1.4 Ma), Gombore Iδ (1.3 Ma) a…
2021
International audience; While the emergence of the Acheulean is well documented in East Africa at ~1.7 Ma, subsequent developments are less well understood and to some extent controversial. Here, we provide robust evidence regarding the time period between 1.6 Ma and 1.2 Ma, based on an interdisciplinary approach to the stratigraphic sequences exposed in the Gombore gully of Melka Kunture, in the upper Awash Valley of Ethiopia. Throughout the Pleistocene, the environment differed significantly from elsewhere in Africa because of the elevation at 2000 m asl, the cooler and rainy climate, the Afromontane vegetation, the development of endemic animal species, and the recurrent impact of volcan…
Are aquatic and semiaquatic true bugs (Hemiptera: Nepomorpha; Gerromorpha) distinct aquatic communities? A case study in homogeneous habitats
2019
We investigated the environmental factors influencing Nepomorpha and Gerromorpha in lentic, highly vegetated habitats from the Danube Delta. We collected 7032 individuals from 12 species from 23 ha...
Disentangling the latitudinal and altitudinal shifts in community composition induced by climate change: The case of riparian birds
2021
11 pages; International audience; Aim: This study investigates whether, and how, the composition of riparian bird communities has been affected by climate warming and habitat change. Although these two forces act separately, their respective contributions are rarely examined. Moreover, while the response of a given community may be a function of latitude and altitude, most studies have focused on these gradients separately. Riparian ecosystems are an opportunity to investigate community change along latitudinal and elevational gradients.Location: France, three major rivers (the Doubs, the Allier and the Loire)Taxon: Birds.Methods: Drawing upon bird community monitoring data over a period of…
Forest multifunctionality is not resilient to intensive forestry
2021
AbstractThere is ample evidence that intensive management of ecosystems causes declines in biodiversity as well as in multiple ecosystem services, i.e., in multifunctionality. However, less is known about the permanence and reversibility of these responses. To gain insight into whether multifunctionality can be sustained under intensive management, we developed a framework building on the concept of resilience: a system’s ability to avoid displacement and to return or transform to a desired state. We applied it to test the ability of forest multifunctionality to persist during and recover from intensive management for timber production in a boreal forest. Using forest growth simulations and…
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…