943 resultados para Geology>Paleontology>Vertebrate Paleontology
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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O presente trabalho compreende o estudo geológico e paleontológico detalhado da litofácies recifal da Formação Pirabas, Estado do Pará, aflorante na Praia do Maçarico, município de Salinópolis, como um corpo pequeno, isolado e lenticular, que deve ter se desenvolvido na rampa interna da plataforma do Mar de Pirabas. O conteúdo biótico é rico e variado, composto por três grupos de algas coralíneas, poríferos, corais, briozoários, equinoides, foraminíferos, ostracodes, e moluscos. Foram reconhecidos neste recife em mancha três estágios de sucessão ecológica, estabilização, colonização e diversificação, onde as finas crostas micríticas reconhecidas na parte superior do estágio diversificação indicam degradação das condições ambientais favoráveis à acreção recifal, provavelmente devido a continentalização do sítio deposicional. O exame petrográfico revelou apenas uma microfácies deposicional, biomicrito, sem consideráveis variações texturais e composicionais. A cimentação marinha é predominante, representada por massas microcristalinas e cimentos micríticos, localmente neomorfisados para bioesparito, e detritos carbonáticos advindos do fluxo biogênico inconsolidado, resultantes principalmente da dispersão de cristais de aragonita dos fragmentos algálicos, acumulados sob a forma de lama micrítica. Para a gênese da bioconstrução as algas foram fundamentais na consolidação e modelagem do arcabouço, principalmente as macroalgas vermelhas, decisivas para a proteção e cimentação dos demais organismos.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Anchitherine horses are a subfamily of equids that are abundantly represented in the late Eocene and early Oligocene of North America. This group has been heavily studied in the past, but important questions still remain. Some studies have focused on the Eocene-Oligocene boundary and have used these equids along with other taxa to study mammalian diet and climate change through this interval. I reexamine two anchitherine genera, Mesohippus and Miohippus, from stratigraphic sequences of the White River Group in western Nebraska and southwestern South Dakota. These sequences span the Chadronian (late Eocene), Orellan (early Oligocene), and Whitneyan (early Oligocene) North American land-mammal ages. The most recent revision of these genera was done by Prothero and Shubin (1989). I review the characters used for taxonomic identification. This includes characters such as the hypostyle, the articular facet on the third metatarsal, and dental dimensions. To avoid possible biases caused by combining specimens from different stratigraphic levels, specimens were separated by location and stratigraphic level. The length and width of cheek teeth, and tooth rows were measured on 488 specimens. First molar area serves as a proxy for body mass in horses and other mammals, and can be useful for distinguishing among species. Results indicate that the characters used by Prothero and Shubin were highly variable in anchitherine horses and are not useful for distinguishing between these genera. The development of the articular facet on the third metatarsal may be a function of body size and therefore may be of no more utility than first molar area. Variability in first molar area suggests the presence of three species in the medial and late Chadronian, two species in the Orellan, and at least two species in the Whitneyan. Due to a lack of objective criteria separating Mesohippus from Miohippus, I recommend synonymy of these genera, making Mesohippus a junior subjective synonym.
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The study of the micro-fauna of Montana formations has been almost entirely neglected. Because the petroleum industry of this state has not felt the necessity for using micro-paleontology in its sub-surface correlations, the science has been but little used. The Montana Power Company has had an examination made of some of its well cuttings by a competent micro-paleontologist who found some foraminifera in Mesozoic sediments. However, no investigations have been made to determine the presence and character of the micro-fauna of the Paleozoic formations of Montana.
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no. 01-18
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El objetivo de este trabajo es determinar la existencia de diferencias de género en la distribución de las firmas de los trabajos de paleontología de vertebrados, analizando el caso de la revista argentina Ameghiniana, desde 1957 hasta 2011. Mediante el método bibliométrico se estudia la distribución y evolución por género de las firmas de los autores, su productividad, procedencia geográfica, composición de las firmas (autorías y coautorías), orden de mención de autores, taxón estudiado y niveles de citación alcanzados. Los resultados muestran un predominio del género masculino en el número de firmas, en las tasas de productividad media anual y en los niveles de citación. No se encontraron diferencias significativas entre el género y los taxones estudiados ni en el orden de las firmas, pero sí en la variable "procedencia geográfica" de los autores. Se concluye que en los estudios de paleontología de vertebrados publicados en Ameghiniana se mantiene la tradición masculina que caracteriza a la disciplina. Sin embargo, el incremento de firmas de mujeres durante todo el periodo, la equiparación de la productividad en la última década y el aumento de coautorías mixtas son claras señales de una tendencia de cambio
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A detailed sedimentological and paleontological analysis of the uppermost Miocene (Messinian)–Pliocene boundary at the northern border of the Bajo Segura Basin, southeastern Spain, was carried out in order to describe the evolution of the regional paleocoastline during the Pliocene reflooding of the Mediterranean immediately after the sea-level fall related to the Messinian Salinity Crisis. Multiple trace fossils typical of firm- and hardgrounds were recognized, allowing identification of Glossifungites (two different types), Entobia, and Gnathichnus ichnofacies. Trace-fossil analysis showed that lithology and media consistency exerted considerable control on the development of the different ichnocoenoses and that there was a clear decrease in hydrodynamic energy from a coastal to a shallow-water shelf environment related to progressive sea-level rise. Ichnological and sedimentological data provide evidence that the definitive flooding of the Mediterranean was rapid and synchronous throughout the northern margin of the Bajo Segura Basin. The following model for the Pliocene transgression in the study area is therefore proposed: (1) the marine ingression penetrated along the incised paleovalleys carved as a consequence of the fall in sea level, where the first two Pliocene systems were deposited (P0–P1); (2) during the maximum flooding surface of the transgression, the sea overflowed the margins of the paleovalleys and extended throughout the entire northern margin of the basin; and (3) the third Pliocene system was deposited, forming the lower part of a highstand systems tract (P2).
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El objetivo de este trabajo es determinar la existencia de diferencias de género en la distribución de las firmas de los trabajos de paleontología de vertebrados, analizando el caso de la revista argentina Ameghiniana, desde 1957 hasta 2011. Mediante el método bibliométrico se estudia la distribución y evolución por género de las firmas de los autores, su productividad, procedencia geográfica, composición de las firmas (autorías y coautorías), orden de mención de autores, taxón estudiado y niveles de citación alcanzados. Los resultados muestran un predominio del género masculino en el número de firmas, en las tasas de productividad media anual y en los niveles de citación. No se encontraron diferencias significativas entre el género y los taxones estudiados ni en el orden de las firmas, pero sí en la variable "procedencia geográfica" de los autores. Se concluye que en los estudios de paleontología de vertebrados publicados en Ameghiniana se mantiene la tradición masculina que caracteriza a la disciplina. Sin embargo, el incremento de firmas de mujeres durante todo el periodo, la equiparación de la productividad en la última década y el aumento de coautorías mixtas son claras señales de una tendencia de cambio
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Mode of access: Internet.
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Thesis (M.S. in Geology)--University of California, Berkeley, 1914.