39 resultados para fossil record
Resumo:
We present a new insight on NGC 6034 and UGC 842, two groups of galaxies previously reported in the literature as being fossil groups. The study is based on optical photometry and spectroscopy obtained with the CTIO Blanco telescope and Sloan Digital Sky Survey archival data. We find that NGC 6034 is embedded in a large structure, dominated by three rich clusters and other small groups. Its first and next four ranked galaxies have magnitude differences in the r band and projected distances which violate the optical criteria to classify it as a fossil group. We confirm that the UGC 842 group is a fossil group, but with about half the velocity dispersion that is reported in previous works. The velocity distribution of its galaxies reveals the existence of two structures in its line of sight, one with sigma(nu) similar to 223 km s(-1) and another with sigma(nu) similar to 235 km s(-1), with a difference in velocity of similar to 820 km s(-1). The main structure is dominated by passive galaxies, while these represent similar to 60% of the second structure. The X-ray temperature for the intragroup medium of a group with such a velocity dispersion is expected to be kT similar to 0.5-1 keV, against the observed value of kT similar to 1.9 keV reported in the literature. This result makes UGC 842 a special case among fossil groups because (1) it represents more likely the interaction between two small groups, which warms the intragroup medium and/or (2) it could constitute evidence that member galaxies lost energy in the process of spiraling toward the group center, and decreased the velocity dispersion of the system. As far as we know, UGC 842 is the first low-mass fossil group studied in detail.
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A new species of Spiranthera A. St.-Hil. (Rutaceae, Galipeinae) is illustrated and described from Espirito Santo, Brazil. Spiranthera atlantica Pi rani represents the first species record for the genus in the Atlantic Forest of eastern Brazil. The new (axon resembles the Amazonian S. guianensis Sandwith but differs by its smaller, few-flowered inflorescences and by the fruit and leaflet morphology.
Resumo:
Adamussium Jonkersi sp nov is described from the Late Oligocene Destruction Bay Formation Wrona Buttress area King George Island (South Shetlands) West Antarctica The unit characterized by volcanic sandstone is a shallow marine( succession deposited in a moderate- to high-energy environment The thin shelled pectinids collected from the lower part of the unit are preserved mostly as complete valves Shell thickness sculpture pattern and umbonal angle suggest a free-living inactive swimming life habit
Resumo:
The stomatal density and index in compressed leaves of Glossopteris communis from two different roof shales from the Lower Permian in Parana Basin, Brazil (Western Gondwana) have been investigated to test the possible relationship with modeled global changes in atmospheric CO(2) during the Phanerozoic. The obtained parameters show that the genus Glossopteris from the Cool Temperate biome can be used as CO(2) -proxy, despite the impossibility of being compared with living relatives or equivalents. When confronted with already published data for the Tropical Summer Wet biome, the present results confirm the detection of low levels of atmospheric CO(2) during the Early Permian, as predicted by the modeled curve. Nevertheless, the lower stomatal numbers detected at the climax of the coal interval (Faxinal Coalfield, Sakmarian) when compared to the higher ones obtained in leaves from a younger interval (Figueira Coalfield, Artinskian) could be attributed to temporarily high levels of atmospheric CO(2). Therefore, the occurrence of an extensive peat generating event at the southern part of the basin and subsequent greenhouse gases emissions from this environment may have been enough to reverse regionally and temporarily the reduction trend in atmospheric CO(2). Additionally, the Faxinal flora is preserved in a tonstein layer, which is a record of volcanic activity that could also cause a rise in atmospheric CO(2). During the Artinskian, the scarce generation of peat mires, as revealed by the occurrence of thin and discontinuous coal layers, and the lack of volcanism evidence would be insufficient to affect the general low CO(2) trend.
Resumo:
Changes in the oxygen isotopic composition of the planktonic foraminifer Globigerinoides ruber and in the foraminifera faunal composition in a core retrieved from the southeastern Brazilian continental margin were used to infer past changes in the hydrological balance and monsoon precipitation in the western South Atlantic since the Last Glacial Maximum (LGM). The results suggest a first-order orbital (precessional) control on the South American Monsoon precipitation. This agrees with previous studies based on continental proxies except for LGM estimates provided by pollen records. The causes for this disagreement are discussed.
Resumo:
(Notes on Acaulospora bireticulata Rothwell & Trappe and first record of Acaulospora koskei Blask. from Brazil). Our knowledge of species distribution in arbuscular mycorrhizal fungi (AMF) is still limited and morphological variations found in isolates of one species may provide additional insight for understanding the characters used in the taxonomy of this group. The aims of this work were to expand biogeographical data regarding Acaulospora koskei Blaszk. and Acaulospora bireticulata Rothwell & Trappe, both found in an Araucaria Forest in Sao Paulo state, Brazil, as well as to compare the descriptions of these species with those of other similar AMF.
Resumo:
Northeastern Brazil represents a strategic area in terms of Quaternary records of environmental changes in South America due to its distinct semi-arid climate in near equatorial latitudes. In this study, carbon isotope and charcoal distribution records in soils are used to characterize vegetation dynamics, forest fires and their relation to climate change since the Late Pleistocene in the States of Ceara, Piaui and Paraiba, Northeastern Brazil. At the Ceara site, the carbon isotope record showed an enrichment trend from -24%(o) to 19%(o) during the early-mid Holocene, indicating an opening of vegetation and expansion of savanna vegetation (C(4) plants) during this period. A trend toward more depleted delta(13)C values (similar to-32%.) in the late Holocene indicates an expansion of forest vegetation (C(3) plants). A similar trend is observed at the Piaui and Paraiba sites where values of similar to-24%0 are associated with open forest vegetation during the late Pleistocene. In the early-mid Holocene, delta(13)C values of up to -18.0%(o), suggest the expansion of C4 plants. Based on the carbon isotope data, it is postulated that from similar to 18,000 cal yr B.P. to similar to 11,800 cal yr B.P.-similar to 10,000 cal yr B.P. arboreal vegetation was dominant in northeastern Brazil and is associated with humid climates. The savanna expanded from similar to 10,000 cal yr B.P. to similar to 4500-3200 cal yr B.P. due to a less humid/drier climatic phase, also supported by the significant presence of fires (charcoal fragments in the soil). From approximately 3200-2000 cal yr B.P. to the present, carbon isotope records suggest forest expansion and a more humid phase. These results form part of a regional pattern since they are in agreement with paleovegetation records obtained in regions of Maranhao, northeastern Brazil and in the Amazon and Rondonia States, northern Brazil. (C) 2010 Elsevier B.V. All rights reserved.
Resumo:
Colleters are widely occurring in eudicots showing relevant taxonomic importance in several families. Nevertheless, there are few records in monocots, restricted to only one description of these glands in Orchidaceae. The genus Oncidium is polyphyletic, currently the subject of taxonomic studies. In this context, the secretory structures can be an important diagnostic character that may help in the delineation of this group. O. flexuosum Sims presents colleters in vegetative - leaf primordium of protocorms, apical and axillary buds in the mature rhizomes - and reproductive organs - at the base of bracts, bracteoles and sepals. All the colleters observed are finger-like trichomes, composed of two uniseriated cells, where the apical one is elongated and possesses dense cytoplasm. The exsudate accumulates in a subcuticular space. causing displacement of the cuticle. Histochemical tests indicate the presence of mucilage in association with lipophilic and proteinic compounds inside the secretory cell. Secretion is abundant, hyaline and slightly viscous. The localization of the trichomes and their exsudate indicate the involvement of these colleters with the protection of meristematic regions in vegetative and reproductive organs. These results can be useful in the taxonomy of the genus Oncidium and for future studies about colleters in monocots. (C) 2010 Elsevier GmbH. All rights reserved.
Resumo:
A new Sciophilinae-Azana atlantica, sp. n. - is described from the Atlantic Forest in southeastern Brazil. The species has a number of distinctive apomorphic features, including loss of the mid ocellus, reduced mouthparts, Sc short and incomplete, first section of Rs missing, r-m elongated, longitudinal in position, aligned with the second section of Rs ( R(5)), unforked medial and cubital veins, R(4) missing, M(4) entirely absent, gonostyle triangular, with an inner row of elongated spines and a basal, digitiform inner projection. Some of these features are shared with other genera of the Azana-group of Sciophilinae. The shape of the scutum and the strong spines on the gonostyle make it clear that the species belongs in Azana, despite the features that are distinctive from the remaining species in the genus. There are ten species described in Azana to date, from United States, Europe, Sri Lanka, Canary Islands, tropical Africa and Baltic amber. This is the first Neotropical species belonging to the genus. The complete loss of M(4) and the separated gonocoxites suggest that Azana atlantica, sp. n. forms a monophyletic group with the Afrotropical species of the genus. Azana, Morganiella, Neoaphelomera, Neotrizygia, and Trizygia are shown to compose a small clade within the Azana-group of genera. The division of the genus into two subgenera - A. ( Azana) and A. ( Jugazana) - most probably renders A. ( Azana) paraphyletic and it is suggested that this should be for the time being abandoned.
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(Triphora uniflora A.C. Ferreira, Baptista & Pansarin (Orchidaccae: Triphorcae): a new species and the first record of the genus Triphora Nutt. for Sao Paulo state, Brazil). Triphora uniflora A. C. Ferreira, Baptista & Pansarin, a new species of Orchidaceae, is described and illustrated. Furthermore, this is the first report of the genus Triphora for Sao Paulo state, Brazil. The relationship of this new species to other taxa of the genus and the need to preserve the natural habitat of this Triphora species are discussed.
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The globular cluster HP 1 is projected on the bulge, very close to the Galactic center. The Multi-Conjugate Adaptive Optics Demonstrator on the Very Large Telescope allowed us to acquire high-resolution deep images that, combined with first epoch New Technology Telescope data, enabled us to derive accurate proper motions. The cluster and bulge fields` stellar contents were disentangled through this process and produced an unprecedented definition in color-magnitude diagrams of this cluster. The metallicity of [Fe/H] approximate to -1.0 from previous spectroscopic analysis is confirmed, which together with an extended blue horizontal branch imply an age older than the halo average. Orbit reconstruction results suggest that HP 1 is spatially confined within the bulge.
Resumo:
The end of the Neoproterozoic era is punctuated by two global glacial events marked by the presence of glacial deposits overlaid by cap carbonates. Duration of glacial intervals is now consistently constrained to 3-12 million years but the duration of the post-glacial transition is more controversial due to the uncertainty in cap dolostone sedimentation rates. Indeed, the presence of several stratabound magnetic reversals in Brazilian cap dolostones recently questioned the short sedimentation duration (a few thousand years at most) that was initially suggested for these rocks. Here, we present new detailed magnetostratigraphic data of the Mirassol d`Oeste cap dolostones (Mato Grosso, Brazil) and ""bomb-spike"" calibrated AMS (14)C data of microbial mats from the Lagoa Vermelha (Rio de Janeiro, Brazil). We also compile sedimentary, isotopic and microbiological data from post-Marinoan outcrops and/or recent depositional analogues in order to discuss the deposition rate of Marinoan cap dolostones and to infer an estimation of the deglaciation duration in the snowball Earth aftermath. Taken together, the various data point to a sedimentation duration in the range of a few 10(5) years. (C) 2010 Elsevier B.V. All rights reserved.
Resumo:
Laurencia marilzae Gil-Rodriguez, Senties & MT Fujii is recorded for the first time for the tropical western Atlantic Ocean, occurring in Isla Mujeres, Quintana Roo, Mexican Caribbean. The specimens were collected in November 2008 and June 2009, growing epilithically in the lower intertidal zone on moderately exposed rocky shores. This species is characterized by its distinctive yellow-orange color in the natural environment, four pericentral cells per vegetative axial segment, the presence of secondary pit-connections between adjacent cortical cells, which are markedly projecting at the apices, and by the presence of one ""corp en cerise"" per cell in all cells of the thallus: cortical, medullary, including pericentral and axial cells, and trichoblasts. Morphological similarities and molecular data support the determination of this material as L. marilzae. The present study expands the geographical distribution of L. marilzae to the Caribbean Sea in the tropical Western Atlantic Ocean.
Resumo:
This first record of vivipary in the Amaranthaceae is reported for the foredune plant Alternanthera littoralis var. maritima (July 2008, northern coast of Brazil). Vivipary is the precocious and uninterrupted growth of the seedlings while still attached to the maternal body. We propose a hypothesis for the viviparous germination of this species based on field observations. Our record adds new perspectives to the reproductive biology of the Amaranthaceae.
Resumo:
Palisada flagellifera (Ceramiales, Rhodophyta) is recorded for the first time in the eastern Atlantic Ocean off Tenerife, La Gomera, La Palma and Fuerteventura, Canary Islands, Spain. The specimens were collected in 2006-2009 growing from the lower intertidal to subtidal zones to 2 m depth at sites exposed to wave action. The species possesses a palisade-like arrangement of cortical cells in cross section, lacks secondary pit connections between them, and has tetrasporangia produced by three fertile pericentral cells (the third and the fourth additional and the second that becomes fertile), and a right-angled arrangement of tetrasporangia. Gametangia were not observed. The phylogenetic relationships were inferred by analyses of the chloroplast-encoded rbcL gene sequences from 46 taxa. The Canarian and Brazilian P. flagellifera specimens formed a highly supported clade with a low level of genetic variation in the rbcL sequences (0.02-0.04%), confirming that they are the same taxonomic entity. This study expands the geographical distribution of P. flagellifera to the eastern Atlantic Ocean.