A New Omomyid Primate from the Earliest Eocene of Southern England: First Phase of Microchoerine Evolution

Hooker, J.J. 2012. A new omomyid primate from the earliest Eocene of southern England: First phase of microchoerin

Paleogene palynostratigraphy of the eastern middle Magdalena Valley, Colombia

This work presents a detailed study of the pollen and spore distribution in the Paleocene-Eocene Lisama and La Paz Formations on the eastern border of the Middle Magdalena Valley, Colombia. One hundred and forty-seven samples obtained from cores and outcrops were prepared for palynological research, fifty-nine of which were rich in pollen and spores. Three hundred spore and pollen taxa were identified. The studied stratigraphic interval is a 2000 m thick coastal and fluvial deposit formed in a variable subsiding tectonic setting. The Lisama Formation is characterized by the dominance of the Proxapertites group. Some typical Paleocene forms start to disappear toward the upper part of the Lisama Formation (e.g.Bombacacidites annae, Ephedripites vanegensis, Retidiporites magdalenensis), and are followed by a barren interval probably linked to intense oxidation during paleosol development (the uppermost 266 m of the Lisama Formation). In the La Paz Formation there is a progressive appearance of early and middle Eocene species (e.g. Cyclusphaera scabrata, Foveotriporites hammenii, Monoporopollenites annulatus, Perfotricolpites digitatus, Spirosyncolpites spiralis, Striatopollis catatumbus, Bombacacidites gonzalezii). This biostratigraphic evidence indicates that an early-middle Eocene hiatus in the eastern area of the Middle Magdalena Valley basin is not present, as many authors have previously suggested. One new pollen genus, Foveomonoporites, and two new pollen species, Foveomonoporites variabilis and Psilamonocolpites operculatus are described and illustrated

Nestin Promotes the Phosphorylation-dependent Disassembly of Vimentin Intermediate Filaments During Mitosis

The expression of the intermediate filament (IF) protein nestin is closely associated with rapidly proliferating progenitor cells during neurogenesis and myogenesis, but little is known about its function. In this study, we examine the effects of nestin expression on the assembly state of vimentin IFs in nestin-free cells. Nestin is introduced by transient transfection and is positively correlated with the disassembly of vimentin IFs into nonfilamentous aggregates or particles in mitotic but not interphase cells. This nestin-mediated disassembly of IFs is dependent on the phosphorylation of vimentin by the maturation/M-phase–promoting factor at ser-55 in the amino-terminal head domain. In addition, the disassembly of vimentin IFs during mitosis appears to be a unique feature of nestin-expressing cell types. Furthermore, when the expression of nestin is downregulated by the nestin-specific small interfering RNA in nestin-expressing cells, vimentin IFs remain assembled throughout all stages of mitosis. Previous studies suggest that nonfilamentous vimentin particles are IF precursors and can be transported rapidly between different cytoplasmic compartments along microtubule tracks. On the basis of these observations, we speculate that nestin may play a role in the trafficking and distribution of IF proteins and potentially other cellular factors to daughter cells during progenitor cell division

eEdad 40Ar/39Ar para la biota de plantas, anuros e insectos del Eoceno Temprano de Pampa de Jones (Formación Huitrera, provincia del Neuquén, Argentina)

The Pampa de Jones fossil site, a stratigraphically isolated roadcut near the northeastern shore of Nahuel Huapi Lake in Neuquén Province, Argentina, holds a rich fossil biota including a macroflora, a microflora, insects, and most famously, an ontogenetic series of pipid frogs. The site exposes tuffaceous mudstone and sandstone beds of probable lacustrine origin, considered to belong to the volcanic Huitrera Formation. However, there have been no reliable age constraints for the fossil assemblage. We undertook laser fusion analyses of sanidine and biotite crystals occurring in a tuff layer found 4.4 m above the main fossil horizon. Twentyeight sanidine crystals yielded an 40ArZ39Ar age of 54.24 ± 0.45 Ma that is preferred over our biotite age of 53.64 ± 0.35 Ma. Pampa de Jones is thus the oldest well-dated Eocene fossil site in Patagonia, predating two other recently 40Ar/39Ar-dated sites: Laguna del Hunco (51.91 ± 0.22 Ma) and Rio Pichileufu (47.46 ± 0.05 Ma). The improved age control makes possible a finer scale of evolutionary hypothesis testing and turnover analysis in the region. The age is concordant with the site's placement in the Huitrera Formation and a depositional origin related to Early Paleogene arc volcanism, and it correlates to an interval of significant climate fluctuations following the Paleocene-Eocene boundary. ©Asociación Paleontológica Argentina.La localidad de Pampa de Jones es un afloramiento estratigráficamente aislado, cercano a la costa noreste del Lago Nahuel Huapi en la Provincia del Neuquén, Argentina. Contiene una rica biota fósil que incluye macroflora, microflora, insectos y una reconocida serie ontogenética de pípidos. La secuencia estratigráfica consiste de fangolitas y areniscas tufáceas de probable origen lacustre, asignada a la Formación Huitrera. La ausencia de datos geocronológicos directos ha impedido la estimación de edades confiables para esta paleobiota. En este trabajo se analizan por fusión láser los cristales de sanidina y biotita presentes en un nivel de toba ubicado a 4.4 m por encima del principal horizonte fosilífero. Veintiocho cristales de sanidina arrojaron una edad 40Ar/39Ar de 54.24 ± 0.45 Ma, la cual se prefiere a la edad de 53.64 ± 0.35 Ma estimada a partir de la biotita. La biota de Pampa de Jones es la más antigua del Eoceno de Patagonia datada radiométricamente, y precede a las dos localidades Eocenas datadas en la región: Laguna del Hunco (51.91 ± 0.22 Ma) y Río Pichileufú (47.46 ± 0.05 Ma). El control cronológico ajustado permitirá evaluar hipótesis evolutivas y analizar recambios en la región con una mayor resolución temporal. La edad obtenida concuerda con la ubicación de la secuencia dentro de la Formación Huitrera y con el origen de los depósitos asociados al volcanismo de arco del Paleógeno temprano, y se correlaciona con un lapso de significativas fluctuaciones climáticas ocurridas con posterioridad al pasaje Paleoceno-Eoceno.Fil: Wilf, Peter. State University of Pennsylvania; Estados UnidosFil: Singer, Brad S.. University of Wisconsin; Estados UnidosFil: Zamaloa, María del Carmen. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Johnson, Kirk R.. Denver Museum of Nature & Science; Estados UnidosFil: Cúneo, Néstor Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentin