1,720,962 research outputs found
Chubutolithes gaimanensis and other wasp ichnofossils: breaking through the taphonomic barrier
Get PDFWasp ichnofossils are scarce in the record because of their low preservational potential. Evidence comprises perforations in bee cells, cocoons, and paper and mud nests, whose preservation may involve the most unusual taphonomic processes. The record includes trace fossils preserved in other trace fossils; paper nests preserved in amber, ironstones and caves; and fragile trace fossils preserved in conglomerates. Evidence for wasps is weak in some cases and more reliable in others. Perforations in bee cells can be attributed to other insects; likewise cocoons can be attributed to other insects and other organic and inorganic processes. Some fossil paper and mud nests are the most reliable wasp ichnofossils. Brownichnus favosites preserved in ironstone and in Dominican amber, provide the oldest records of polistines known. One of the best-known examples of wasp ichnofossils is Chubutolithes gaimanensis, preserved in intraclast conglomerates. New ichnological and sedimentological evidence suggests that cells were constructed around plant stems from which they could have dropped to the soil, been covered with sediments, impregnated with carbonate, and then reworked by fluvial action along with other carbonate nodules.Fil: Genise, Jorge Fernando. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cladera, Gerardo. Museo Paleontológico Egidio Feruglio; Argentin
First Record of an Extinct Marabou Stork in the Neogene of South America
Get PDFWe describe a new large species of marabou stork, Leptoptilus patagonicus(Ciconiiformes, Ciconiidae, Leptoptilini), from the late Miocene Puerto Madryn Formation, Chubut Province, Argentina. The specimen consists mainly of wing and leg bones, pelvis, sternum, cervical vertebrae, and a few fragments of the skull. We provisionally adopt the traditional system− atic scheme of ciconiid tribes. The specimen is referred to the Leptoptilini on the basis of similarities in morphology and intramembral proportions with the extant genera Ephippiorhynchus, Jabiru, and Leptoptilos. The fossil specimen resembles in overall morphology and size the species of Leptoptilos, but also exhibits several exclusive characters of the sternum, hu− merus, carpometacarpus, tibiotarsus, and pelvis. Additionally, its wing proportions differ from those of any living taxon, providing support to erect a new species. This is the first record of the tribe Leptoptilini in the Tertiary of South America.Fil: Noriega, Jorge Ignacio. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Cladera, Gerardo. Museo Paleontológico Egidio Feruglio; Argentin
Early Cretaceous riparian vegetation in Patagonia, Argentina
Get PDFEarly Cretaceous riparian vegetation in Patagonia, Argentina. An autochthonous plant as-semblage found at the Bajo Grande locality, Anfiteatro de Ticó Formation, Baqueró Group, Early Aptian of Santa Cruz province, Argentina, is described. Sedimentological data show an alternation of sandstone and lime-stone, with recurrent fossil levels associated to a fluvial system. The frequent flood in areas close to the levee had an influence on the vegetation growing along the banks of the channels. A plant assemblage composed of Ricciopsis grandensis nov. sp. (bryophyte), Adiantopteris tripinnata nov. sp., Schizaeaceae pinnules (ferns), and the gnetalean fructification Ephedra verticillata nov. sp. was found in this paleoenvironment. The taphonomical studies suggest that the plant assemblage was autochthonous, and it grew and was buried in an area near a levee. This result is congruent with environmental data provided by living representative of the fossil taxa analyzed.Fil: Cladera, Gerardo. Museo Paleontológico Egidio Feruglio; ArgentinaFil: del Fueyo, Georgina Marisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Villar, Liliana Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Archangelsky, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin
Palynology and paleoenvironments of the Bajo Comisión section, Cretaceous of Santa Cruz province, Argentina
Get PDFEl perfil de la clásica localidad Bajo Comisión, originalmente estudiada por T. Halle, ha brindado información estratigráfica adicional. Se determinaron más de 200 especies de palinomorfos recuperados de 16 niveles fértiles a lo largo de la columna de 272 m de espesor asignada al Albiano. Los tres niveles fértiles inferiores han sido referidos a la Formación Río Mayer, mientras que los niveles restantes corresponden a la Formación Kachaike. Los conteos de los principales grupos palinológicos incluyen niveles marinos en la mitad inferior del perfil. En la columna dominan las Pteridófitas (abundantes Anemiaceae) y Gimnospermas (principalmente Classopollis), mientras que las angiospermas se hallan representadas por algunas especies primitivas con porcentajes moderados a bajos. El ambiente fue dominado por sedimentación deltaica con una moderada influencia marina en la mitad inferior del perfil (prodelta-frente deltaico-planicies subácueas), y típicamente continental (sub-aerea y fluvial) en su mitad superior. La distribución estratigráfica de 80 especies seleccionadas muestra un cambio gradual (en el lapso cronológico que abarca el perfil) de la asociación palinológica. Dos unidades bioestratigráficas mayores se caracterizan por las primeras apariciones o extinciones de varios taxones. Se sugieren otras subdivisiones menores que pueden tener un eventual significado bioestratigráfico. Finalmente, se realizan comparaciones con otras palinofloras de la Cuenca Austral en Santa Cruz.A section at the classical locality Bajo Comisión, originally studied by T. Halle, has provided new stratigraphical data. More than 200 palynological species assigned to the Albian have been determined. They were recovered in 16 fertile horizons along the 272 m thick column. The three lower fertile horizons are referred to the Río Mayer Formation while the other levels belong to the Kachaike Formation. Counts of the main palynological groups include a marine sector in the lower half of the profile. Pteridophytes (abundant Anemiaceae) and gymnosperms (mainly Classopollis) dominate throughout the column, while angiosperms are represented by scarce and moderately varied primitive types. The environment was dominated by deltaic sedimentation (prodelta-deltaic front-subaqueous plains) with a moderate marine influence in the lower part of the column, becoming typically continental (sub-aerial- fluvial) at the upper half of the section. The stratigraphic distribution of 80 selected species shows a gradual and constant change in the composition of the palynological assemblage. Two main biostratigraphic units are characterized by first and last appearences of several taxa. Further subdivisions that may have biostratigraphic significance are also suggested. Finally, comparisons with other palynofloras of the Austral Basin in Santa Cruz province, are made.Fil: Archangelsky, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Archangelsky, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Cladera, Gerardo. Museo Paleontológico Egidio Feruglio; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Palynostratigraphic study of the Early Cretaceous Río Mayer and Kachaike formations at the Quebrada El Moro Section, Austral Basin, southwestern Argentina
Get PDFPalynomorph assemblages have been recovered from the upper levels of the Río Mayer Formation and the basal levels of the Kachaike Formation exposed at the Puesto El Moro Creek, southwest of Santa Cruz Province, Argentina. Forty-five spore species and 25 pollen taxa (including six angiosperms) have been identified. The palynological assemblages of the upper levels of Río Mayer Formation are dominated by pteridophytic spores, while Classopollis is a common element. In the Kachaike Formation, the angiosperm pollen grains are more diverse and abundant than in the underlying unit, and Cheirolepidiaceae pollen continues to dominate. The presence of scarce angiosperm pollen, represented by Clavatipollenites sp., allows reference of the assemblage recorded in the upper levels of the Río Mayer Formation to the Aptian Antulsporites- Clavatipollenites Zone. In addition, the lower levels of the Kachaike Formation are referred to the late Aptian-early Albian, based on the presence of Asteropollis asteroides, Pennipollis peroreticulatus, Clavatipollenites sp. and scarce tricolpate pollen. From the three major stages of the early angiosperm evolution in southern South America that have been previously recognized, the palynoflora of the upper levels of the Río Mayer Formation can be referred to Stage I (late Barremian-Aptian), whereas the assemblages recognized in the Kachaike strata are comparable to Stage II (latest Aptian- earliest Albian).Fil: Perez Loinaze, Valeria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Archangelsky, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Cladera, Gerardo. Museo Paleontológico Egidio Feruglio; Argentin
Arecaceae Fossil Fruits from the Paleocene of Patagonia, Argentina
Get PDFWe describe fossil fruits collected from outcrops of the Salamanca Fm. (Paleocene, Danian, 63. 3-61. 9 Ma) at the Estancia Las Violetas locality, Chubut, Argentina that show affinities with members of the Subtribe Attaleinae, Tribe Cocoseae, Subfamily Arecoideae within the Arecaceae. The fossils are preserved as permineralizations, and were examined by longitudinal, tangential and cross-sections, as well as by the application of Computed Tomography Scanning technology (CT Scan). The fruits are ovoid drupes with 3 longitudinal grooves delimiting three valves; displaying apical stigmatic remains and a single apical germination pore. The exocarp and mesocarp are fused and anatomically indistinguishable one from another; they contain longitudinal fibrous bands with brachysclereids. A centrally placed seed occupies the single locule entirely; the seeds are deltoid with a basal hilum and acuminate tip while the endosperm is ruminate. The taxonomic position of the fossils was explored using phylogenetic analyses of molecular sequences combined with morphological data. Along with the suite of morphological characters that points to an affinity with the Subtribe Attaleinae, Tribe Cocoseae, subfamily Arecoideae, the results of the combined phylogenetic analyses confirm the taxonomic placement. This report constitutes the first confirmed record for the Subtribe Attaleinae worldwide and the first record of fossil palm fruits from Argentina.Fil: Futey, Mary K.. Cornell University; Estados UnidosFil: Gandolfo, Maria A.. Cornell University; Estados UnidosFil: Zamaloa, María del Carmen. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Cúneo, Néstor Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Cladera, Gerardo. Museo Paleontológico Egidio Feruglio; Argentin
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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