Screening efforts at the Gray Fossil Site, Washington County, Tennessee, have yielded a unique and diverse salamander fauna for the southern Appalachian Mio-Pliocene; including at least five taxa from three modern families (Ambystomatidae, Plethodontidae, and Salamandridae) supporting the woodland-pond interpretation of the site. All specimens represent the earliest record of their respective families in the Appalachian Mountains; with the Notophthalmus sp. vertebrae being the only Mio-Pliocene skeletal fossil known for the family Salamandridae in North America. Three types of plethodontid salamander are present, with one type representing the earliest known desmognathine. The desmognathine fossils lend credence to the 'Appalachian' origin of the clade in the Mio-Pliocene. The GFS salamander fauna is predominated by plethodontids; competition is inferred by the presence of several similarly large-sized taxa and is invoked to explain the presence of neotenic individuals in an otherwise amicable terrestrial environment.

Pliocene-Pleistocene sediments in the southeastern Acambay graben, central Mexico have yielded mammal fossils, including Equus simplicidens, cf. Rhynchotherium, ?Camelops, Mammuthus sp., Bison sp., and Antilocapra sp. The fossiliferous sediments include a period of lacustrine sedimentation in the late Pliocene-early Pleistocene that interrupted fluvial and alluvial sedimentation during the early Pliocene and Pleistocene. The sediments deposited in this late Pliocene paleolake record a history of lake level fluctuations, shown by lithologic variations in lacustrine sediments and abundance of vertebrate burrows. Volcanic and tectonic events in the Acambay graben were the major controls on sedimentation during Pliocene-Pleistocene time. Various local volcanic structures produced source rocks for Pliocene-Pleistocene sediments, and intra-arc extensional tectonics caused basin subsidence. Blockage of stream drainages by lava flows or perhaps increased basin subsidence contributed to the appearance of and fluctuations in the lacustrine system during the late Pliocene. Diatom assemblages from lacustrine sediments indicate slightly higher precipitation and humidity than present-day conditions in the Acambay graben. Therefore, climatic forcing may have also contributed to the development of the late Pliocene paleolake in the Acambay graben. Pliocene-Pleistocene volcanic rocks in this part of the Acambay graben range from basaltic andesite to rhyolite. The calc-alkaline composition of these volcanic rocks is similar to others in the modern Mexican Volcanic Belt; they have a continental arc affinity, which is consistent with a tectonic setting within the Mexican Volcanic Belt. The major eruptive episode in the Acambay graben occurred during the early Pliocene, although volcanism, represented by small volcanic structures, continued until the late Pleistocene. This observed decline in volcanism in the Acambay graben correlates with a early Pliocene through Quaternary trenchward migration of volcanism in the Mexican Volcanic Belt.

L'analyse dans des dépôts anciens des isotopes cosmogéniques in-situ, déjà largement employés dans les sédiments de rivières actuelles, a le potentiel de fournir des enregistrements haute résolution, sur des échelles de temps de 10 Ma, de taux de dénudations intégrés sur des bassins versant entiers. Nous avons étendu avec succès cette méthode à des sédiments des piedmonts du Tian-Shan (Chine) et de l'Himalaya (collines Siwaliks, Népal). Ces deux zones sont au coeur de débats sur l'évolution des relations climat/érosion/tectonique depuis ~10 Ma. Quatre sections au Tian-Shan, couvrant ~9 Ma, et une large étendue spatiale autour de cette chaîne, ne montrent pas de brusque accélération de l'érosion il y a ~3-5 Ma. Au contraire, nous observons à l'échelle régionale une augmentation progressive (x 4 entre 9 et 4 Ma) puis une stabilisation entre 4 Ma et l'actuel. Ces résultats suggèrent une influence limitée des cycles glaciaires quaternaires sur les taux d'érosion dans cette zone. Un enregistrement dans les sédiments himalayens ne montre également pas d'augmentation significative de l'érosion depuis ~6.5 Ma. Il est en revanche probablement le témoin de réorganisation des systèmes de drainages et d'évolutions tectoniques dans cette région. Avec ces études, nous avons ainsi pu produire pour la première fois des enregistrements haute résolution de taux d'érosion depuis ~10 Ma, grâce aux isotopes cosmogéniques. Cette méthode étant potentiellement applicable dans de nombreux contextes géologiques et climatiques, elle permettra indubitablement des avancées importantes dans la compréhension des processus de surface actuels et passés / In-situ cosmogenic nuclides analysis in ancient sediment could potentially provide high-resolution records of denudation rates, integrated over whole drainage basins, and on several million-year time scales. We successfully extended this method to sediments from the Tianshan (China), and the Himalayas (Nepal) piedmonts. These two areas are at the core of ongoing debates on climate-erosion-tectonics relationships since ~10 Ma. Four sections in the Tianshan, covering ~9 Myr and a broad spatial extent around this range, do not display a brutal increase in denudation at 3-5 Ma. On the other hand, they show at the regional scale a progressive increase (x4 between 4-9 Ma) and a subsequent stabilization since ~4 Ma. These results suggest a limited influence of Quaternary glaciations on erosion in this region. One section in the Himalayan piedmont (Siwaliks hills), neither display any significant increase since ~6.5 Ma that would be link to a major climatic shift. It has nevertheless probably recorded reorganizations of the drainage system and tectonics evolutions in this region. With these studies, we were able to produce the first cosmogenic nuclides-based high resolution records of denudation rates over 10 Myr. This method being potentially applicable in many geological and climatic settings, it will indubitably allow further advances in our understanding of past and present surface processes

The present thesis surveys topic of taxonomic diversity and phylogeny of bears (Mammalia, Ursidae) and aspects of its contextual setting under effects of changing conceptual and methodological viewpoints. This problem is studied from several perspectives. The historical perspective is represented by a critical overview of the history of specific and infraspecific classification of bears with special respect to mutual influences of this classification and theoretical concepts of species accepted in particular periods. The perspective of material approach is exemplified by a material-based study of taxonomical and phyletic status of selected Pliocene to Middle Pleistocene ursine taxa. Along with deconstruction of some traditional hypotheses this produced a model explaining species diversification in ursine bears and its discussion in terms of factual relevance of included background concepts. In the pre-evolutionary period the bear species were usually understood broadly, as incipient immanent entities, yet exhibiting obvious certain infraspecific variability. This was established using definitions of varieties (mostly not identifiable with present subspecies or infraspecific taxa) considered as unstable modes of particular species. Although, in the post-Darwinian period, the concept and taxonomic...

Ce mémoire présente l'étude du signal phytolithique de sédiments mio-pliocènes du Tchad(Afrique Centrale) datés entre 7-2 Ma, et contemporains des Homininés anciens Sahelanthropustchadensis et Australopithecus bahrelghazali. Une calibration de la relation plantes-phytolithes-solspour l'Afrique tropicale subsaharienne actuelle a d'abord été réalisée pour apprécier la signatureenvironnementale des phytolithes dans le registre fossile. L'analyse des assemblages phytolithiques de98 espèces de graminées (Poaceae) a permis d'élaborer trois nouveaux indices phytolithiques à partirde 43 types propres aux Poaceae. Testés sur une base de 57 sols/sédiments modernes du Tchad, cesindices permettent de tracer les associations graminéennes aquatiques du Lac Tchad, les associationsmésophytiques des milieux humides soudaniens, et les associations xérophytiques des milieux secssahéliens. L'analyse des assemblages phytolithiques des sols/sédiments actuels considérés dans leurensemble a permis d'évaluer le potentiel de ce proxy à caractériser la physionomie des formationssoudano-sahéliennes modernes. La calibration a été appliquée à l'étude d'un enregistrementsédimentaire discontinu du Lac Tchad (6-2 Ma) (forage de Bol, 13°N/14°E) et à celle de 18 niveauxpaléontologiques du Djourab (7-3.5 Ma) (16°N/17°E). Les résultats indiquent la présence de savanesintermédiaires à fermées et de zones de végétation aquatique dominantes à 7 Ma dans le Djourab, puisde savanes plus ouvertes et sèches à 3.5 Ma. Une phase de bas niveau lacustre est enregistrée entre3.6-2.8 Ma à Bol, et un pic d'aridité à 3.2 Ma. Enfin, les résultats montrent l'existence de graminéesen C4 au Tchad depuis 7 Ma. / This thesis dissertation is dedicated to the study of the phytolith signal of Mio-Pliocenesediments from Chad (Central Africa) dated between 7-2 Ma, and contemporary to the early Homininspecies Sahelanthropus tchadensis and Australopithecus bahrelghazali. A calibration work studyingthe relationship plants-phytoliths-soils in modern sub-Saharan tropical Africa was carried out in orderto assess the environmental significance of the phytolith signal in the fossil record. Phytolithassemblages produced by 98 sub-Saharan grass species (Poaceae) were analyzed and the results led tothe development of three new phytolith indices defined from 43 types specific to Poaceae. Tested on adatabase of 57 modern soil/sediment samples from Chad, these indices allow drawing aquatic grassassociations of Lake Chad, mesophytic grass associations of wetlands from the Sudanian domain, andxerophytic grass associations of drylands from the Sahelian domain. The analysis of modern soilphytolith assemblages (total assemblages) was used to assess the potential of this proxy to characterizethe physiognomy of the Sudano-Sahelian vegetation types. The calibration had been applied to thestudy of a discontinuous sedimentary record from Lake Chad (6-2 Ma) (Bol core, 13°N/14°E) and of18 paleontological levels from the Djourab (7-3.5 Ma) (16°N/17°E). The results indicate thedominance of intermediate to closed savannas and areas of aquatic vegetation at 7 Ma in the Djourab,and more open and dry savannas at 3.5 Ma. A limited lacustrine stage is recorded between 3.6-2.8 Maat Bol, and a shift of aridity at 3.2 Ma. Finally, the results show the existence of C4 grasses in Chadsince 7 Ma.

La sous-famille des Suinae est largement répandue en Afrique au Plio-Pléistocène et a été abondamment utilisée pour corréler biochronologiquement les sites à hominidés en se basant sur l'évolution morphologique rapide des troisièmes molaires dans différentes lignées. À partir d'un échantillon important de suinés africains actuels, les schémas de variation morphologique crânio-mandibulaire et dentaire sont quantifiés par morphométrie géométrique. Ce référentiel actuel sert à estimer la variabilité morphologique dans le registre fossile. La révision de la paléobiodiversité du genre Kolpochoerus (le suiné plio-pléistocène le plus abondant) dans les bassins du Turkana et de l'Awash s'appuie sur l'étude anatomique et morphométrique de matériels publié et inédit découverts dans la basse vallée de l'Omo (formation de Shungura) et dans la vallée moyenne de l'Awash en Éthiopie. Une nouvelle espèce fossile est décrite, les trajectoires évolutives au sein de chaque espèce sont quantifiées, et les interprétations biostratigraphiques sont révisées. Les liens de parenté au sein du genre Kolpochoerus sont décrits grâce à l'analyse cladistique. L'étude de la paléoécologie des suinés africains est basée sur l'anatomie comparée et la biogéochimie des isotopes stables (carbone et oxygène). Les suinés fossiles présentent une gamme de taille importante, ainsi que des régimes alimentaires et des habitats variés. Les nouvelles connaissances acquises sur leur biodiversité, leur phylogénie, et leur écologie permettent de proposer une histoire paléobiogéographique des Suinae en Afrique. / The subfamily Suinae is widespread in Plio-Pleistocene deposits in Africa, and was heavily used as a biochronological tool to correlate hominid-bearing sites based on the rapid morphological evolution of third molars in different lineages. A large sample of extant African suines enables to quantify patterns of variation in cranio-mandibular and dental morphology using geometric morphometrics. This modern referential is used to estimate the morphological variability in the fossil record. Revision of the paleobiodiversity of the genus Kolpochoerus (the most abundant Plio-Pleistocene suine) in Turkana and Awash basins is based on anatomical and morphometric studies of published and unpublished material discovered in the Lower Omo Valley (Shungura Formation) and in the Middle Awash Valley in Ethiopia. A new fossil species is described, evolutionary trajectories within each species are quantified, and biostratigraphic interpretations are revised. Phylogenetic relationships within the genus Kolpochoerus are described by the cladistic analysis. Paleoecological study of African suines is based on comparative anatomy and stable isotopic biogeochemistry (carbon and oxygen). Fossil suines display a wide range of body size, as well as various diets and habitats. The new results produced regarding their biodiversity, phylogeny, and ecology, enable to reconstruct a paleobiogeographic history of Suinae in Africa.

Member of the genus Sicista rank among the rarest and the least known European mammals. They exhibit a number of outstanding specificities (hibernation, aestivation etc.) and extreme capability of a rare range dynamics. Their fossil record is fragmentary and associated with numerous controversies. The present thesis summarizes results of a detailed revision of the fossil record of Sicista from Czech Republic, Slovakia and some other countries. It comprises of about 150 items of the Holocene and Vistualian age as well as from the Middle and Early Pleistocene including earliest records from MN17/Q1 boundary and type material of S. praeloriger from Q1 Betfia. Compared to a sample of extant population, variation dynamics of both metrical and nonmetrical dental traits was examined in details with particular attention to phenotype patterns of particular fossil samples. The results demonstrated extensive amount of both within- and between-population variation and rather limited validity of commonly used discrimination criteria of extant clades. Nevertheless, we succeeded in species identification of considerable part of numerous Holocene and Vistulian records which revealed (i) a range expansion of S. subtilis s.l. during MIS 3 with persistent distribution in lowland regions of Central Europe in the Late...

Human evolution has been linked to climate change multiple times in the literature. One of the more well-known theories is the ‘savannah’ theory, which states that walking upright became an advantageous character when climate in Africa changed causing drier environments, changing woodlands to savannahs. Human ancestors could cross open fields more easily when walking upright, therefore it was thought that climate change could be a driving factor in the change to bipedal locomotion. Five hominin species were the basis of the study presented here, showing that change towards bipedal locomotion was a mosaic process with gradual change. A review of the relevant literature shows that the timing of change in fossils to bipedal locomotion and climate change do not coincide in the interval 6-3 Ma, therefore suggesting that climate change did not drive human evolution in this case. Changes towards open landscapes with C4 grass dominance peaked at the Pliocene-Pleistocene boundary (2.6 Ma), while the first hominin species already walked completely bipedally before 3.5 Ma.

The Gray Fossil Site, northeastern Tennessee, is formed by multiple karst sub-basins filled with lacustrine sediments. The oldest sediments found were recently dated as Paleo-Eocene by palynological means, whereas the youngest sediments are considered Mio-Pliocene based on their faunal assemblage. In this study, we examined the Mio-Pliocene lacustrine sediments from the Gray Fossil Site to determine the Late Neogene floral characteristics of a site within the southern Appalachian Mountains. The Mio-Pliocene lacustrine sinkhole fill preserves a unique fossil assemblage, which includes invertebrate, vertebrate, and floral remains. Floral remains are represented by wood, seeds, leaves, and pollen grains. Forty-seven palynological samples from six different test-pits were analyzed. All pits exhibit a low pollen yield, a result of basic pH levels, drought, and fire events that occurred during deposition. The palynofloral assemblage has a low to moderate diversity and is largely dominated by a Quercus-Carya-Pinus assemblage (~ 90% of the palynoflora). The presence of Pterocarya grains supports a Late Neogene age for these lacustrine sediments. Comparison with modern pollen-based floras from North America suggests that: (1) examined pits can be discriminated into two separate groups based on their palynofloral signatures, (2) the Mio-Pliocene vegetation at the site ranged between a closed to open woodland setting, depending on the intensity and frequency of drought and fire events, and (3) the fossil palynofloral assemblage is comparable to what would be expected in the modern North American Mesophytic Forest region.

No description available.