Primer registro de Conopeum gray (Electridae, Bryozoa) en el cretácico superior de la Formación Lefipán (Chubut, Patagonia)

La radiación adaptativa del Orden Cheilostomata (Bryozoa) durante el Cretácico Tardío es de particular interés debido a la rápida expansión y evolución explosiva de innovaciones morfológicas que aparecieron en el grupo. Sin embargo, el conocimiento de briozoos cretácicos es muy escaso globalmente, especialmente en Sudamérica y particularmente en Argentina. En la Formación Lefipán se ha reconocido una fauna monoespecífica de briozoos epifíticos sobre hojas de angiospermos fósiles. La Formación Lefipán es una unidad siliciclástica del Maastrichtiano?Daniano en el ámbito NO de la Cuenca Cañadón Asfalto, la cual completa el ciclo de relleno del rift iniciado a principios del Jurásico. Sus condiciones de sedimentación corresponden a depósitos litorales representados por plataformas someras y deltas dominados por mareas. Asimismo se registra en la unidad la transición K/Pg, aunque en un contexto dinámico afectado por la fase marina transgresiva iniciada a fines del Maastrichtiano. Los ejemplares estudiados corresponden a una nueva especie de queilostomado membraniporiformeasignable al género Conopeum. Briozoos modernos de hábitos de crecimiento membraniporiformes son componentes comunes de ambientes marinos de plataforma somera, intermareal a supramareal con niveles de energía moderada a alta y sustratos duros a flexibles. En la actualidad también se registran formas epifíticas de briozoos caracterizadas por ser fotófilos y por habitar ambientes salobres como albuferas, estuarios y deltas presentando hábitos eurihalinos y adaptados a la naturaleza efímera y flexible del sustrato. Tales condiciones se verifican en la Formación Lefipán, por lo que los briozoos identificados confirman interpretaciones previas.Fil: Taboada, César Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Trelew; ArgentinaFil: Pagani, María Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Cúneo, R.. Museo Paleontológico Egidio Feruglio; ArgentinaReunión de Comunicaciones de la Asociación Paleontológica ArgentinaPuerto MadrynArgentinaCentro Nacional Patagónic

Latest Cretaceous, Paleocene and Eocene floras from Patagonia: a critical piece of Gondwana's floral history comes into focus

Patagonia contains a rich and fairly continuous paleobotanical record from the late Maastrichtian to the middle Eocene, an interval known globally for mass extinction and significant climate changes. From this time interval, we have quantitatively collected and stratigraphically studied over 600 species and 20000 specimens from eight wellpreserved compression macrofloras from north-west and central Patagonia. Cretaceous and early Paleocene floras are from coastal environments, whereas the Eocene floras are from volcaniclastic lake sediments. Several sites and stratigraphic levels in the early Paleocene Salamanca Formation show higher richness than comparable Northern Hemisphere floras, but they are relatively impoverished when compared to those of the upper Maastrichtian Lefipan Formation. Probable middle Paleocene floras from the Peñas Coloradas Formation share most species with the Salamanca Formation, but are preserved in fluvial facies. Bedded tuffs at the Eocene sites have yielded precise Ar- Ar dates of 54.24 ±0.45 Ma for the Pampa de Jones flora, 51.91 ±0.22 Ma for the extremely diverse Laguna del Hunco flora, and 47.46 ±0.05 Ma for the similarly rich Río Pichileufú flora. The history of Patagonian plant diversity in the early Paleogene could be linked to a relatively lower effect of the terminal Cretaceous event and high diversification and immigration during Eocene warming. Although the biogeographic signature of the floras is clearly Gondwanic, during the Paleocene there appears to be greater compositional distinctiveness from coeval Australasian floras than in the Eocene, suggesting some degree of endemism after the K-T. The Eocene floras include beautifully preserved examples of extant Australasian tree genera that are now extinct in South America, including Agathis, Papuacedrus, Dacrycarpus, Eucalyptus, Cassuarinaeceae, and Akaniaceae. Paleoclimate analyses based on the macrofloras indicate subtropical and moist growing conditions; during the Eocene there is evidence for true rainforest conditions. These results contribute a considerably improved framework to understanding the plant evolution in Gondwana.Sesiones libresFinanciado: NSF Grants DEB-0919071 and DEB-0345750Financing: NSF Grants DEB-0919071 and DEB-0345750Financiamento: NSF Grants DEB-0919071 and DEB-0345750Facultad de Ciencias Naturales y Muse

X-ray Spectral and Timing evolution of MAXI J1727-203 with NICER

We present a detailed X-ray spectral and variability study of the full 2018 outburst of MAXI J1727-203 using NICER observations. The outburst lasted approximately four months. Spectral modelling in the 0.3-10 keV band shows the presence of both a soft thermal and a hard Comptonised component. The analysis of these components shows that MAXI J1727-203 evolved through the soft, intermediate and hard spectral states during the outburst. We find that the soft (disc) component was detected throughout almost the entire outburst, with temperatures ranging from ∼0.4 keV, at the moment of maximum luminosity, to ∼0.1 keV near the end of the outburst. The power spectrum in the hard and intermediate states shows broadband noise up to 20 Hz, with no evidence of quasi-periodic oscillations. We also study the rms spectra of the broadband noise at 0.3 - 10 keV of this source. We find that the fractional rms increases with energy in most of the outburst except during the hard state, where the fractional rms remains approximately constant with energy. We also find that, below 3 keV, the fractional rms follows the same trend generally observed at energies >3 keV, a behaviour known from previous studies of black holes and neutron stars. The spectral and timing evolution of MAXI J1727-203, as parametrised by the hardness-intensity, hardness-rms, and rms-intensity diagrams, suggest that the system hosts a black hole, although we could not rule out a neutron star

Discovery of optical outflows and inflows in the black hole candidate GRS 1716-249

We present optical spectroscopy obtained with the GTC, VLT and SALT telescopes during the decline of the 2016-2017 outburst of the black hole candidate GRS 1716-249 (Nova Oph 1993). Our 18-epoch data set spans 6 months and reveals that the observational properties of the main emission lines are very variable, even on time scales of a few hours. Several epochs are characterised by P-Cyg (as well as flat-top and asymmetric) profiles in the H$\alpha$, H$\beta$ and He II ($\lambda$4686) emission lines, implying the presence of an accretion disc wind, which is likely hot and dense. The wind's terminal velocity ($\sim$2000 km s$^{-1}$) is similar to that observed in other black hole X-ray transients. These lines also show transient and sharp red-shifted absorptions, taking the form of inverted P-Cyg profiles. We argue that these profiles can be explained by the presence of infalling material at $\sim$1300 km s$^{-1}$. We propose a failed wind scenario to explain this inflow and discuss other alternatives, such as obscuration produced by an accretion-related structure (e.g. the gas stream) in a high inclination system.Comment: Published in MNRAS main journa

An image dataset of cleared, x-rayed, and fossil leaves vetted to plant family for human and machine learning

Leaves are the most abundant and visible plant organ, both in the modern world and the fossil record. Identifying foliage to the correct plant family based on leaf architecture is a fundamental botanical skill that is also critical for isolated fossil leaves, which often, especially in the Cenozoic, represent extinct genera and species from extant families. Resources focused on leaf identification are remarkably scarce; however, the situation has improved due to the recent proliferation of digitized herbarium material, live-plant identification applications, and online collections of cleared and fossil leaf images. Nevertheless, the need remains for a specialized image dataset for comparative leaf architecture. We address this gap by assembling an open-access database of 30,252 images of vouchered leaf specimens vetted to family level, primarily of angiosperms, including 26,176 images of cleared and x-rayed leaves representing 354 families and 4,076 of fossil leaves from 48 families. The images maintain original resolution, have user-friendly filenames, and are vetted using APG and modern paleobotanical standards. The cleared and x-rayed leaves include the Jack A. Wolfe and Leo J. Hickey contributions to the National Cleared Leaf Collection and a collection of high-resolution scanned x-ray negatives, housed in the Division of Paleobotany, Department of Paleobiology, Smithsonian National Museum of Natural History, Washington D.C.; and the Daniel I. Axelrod Cleared Leaf Collection, housed at the University of California Museum of Paleontology, Berkeley. The fossil images include a sampling of Late Cretaceous to Eocene paleobotanical sites from the Western Hemisphere held at numerous institutions, especially from Florissant Fossil Beds National Monument (late Eocene, Colorado), as well as several other localities from the Late Cretaceous to Eocene of the Western USA and the early Paleogene of Colombia and southern Argentina. The dataset facilitates new research and education opportunities in paleobotany, comparative leaf architecture, systematics, and machine learning.Fil: Wilf, Peter. State University of Pennsylvania; Estados UnidosFil: Wing, Scott L.. National Museum of Natural History; Estados UnidosFil: Meyer, Herbert W.. State University of Pennsylvania; Estados UnidosFil: Rose, Jacob A.. State University of Pennsylvania; Estados UnidosFil: Saha, Rohit. State University of Pennsylvania; Estados UnidosFil: Serre, Thomas. State University of Pennsylvania; Estados UnidosFil: Cúneo, Néstor Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Donovan, Michael P.. State University of Pennsylvania; Estados UnidosFil: Erwin, Diane M.. State University of Pennsylvania; Estados UnidosFil: Gandolfo, María A.. Cornell University; Estados UnidosFil: González Akre, Erika. State University of Pennsylvania; Estados UnidosFil: Herrera, Fabiany. National Museum of Natural History; Estados UnidosFil: Hu, Shusheng. State University of Pennsylvania; Estados UnidosFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Johnson, Kirk R.. Smithsonian Tropical Research Institute; PanamáFil: Karim, Talia S.. University of Colorado; Estados UnidosFil: Zou, Xiaoyu. State University of Pennsylvania; Estados Unido