1,721,018 research outputs found
(2151) Proposal to conserve the name Marattiopsis (fossil Marattiaceae) with a conserved type
Full text linkFil: Bomfleur, Benjamin. University Of Kansas; Estados UnidosFil: Escapa, Ignacio Hernan. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Taylor, Edith L.. University Of Kansas; Estados UnidosFil: Taylor, Thomas N.. University Of Kansas; Estados Unido
First evidence of a tetrapod footprint from the Triassic of northern Victoria Land, Antarctica
No full textHere, we report on a tetrapod footprint from the Transantarctic Basin in the far north of Victoria Land, which marks the first record of terrestrial vertebrates for this region. The single specimen derives from a previously unknown lithological unit of Middle or Late Triassic age of the Beacon Supergroup in the Helliwell Hills in the central Rennick Glacier area. It differs in both size and morphology clearly from Middle Triassic trackway types from the upper Fremouw Formation of the Queen Alexandra Range in southern Victoria Land, and likely represents a primitive amniote, procolophonid or therapsid. The footprint is the third evidence of fossil vertebrate trackways in Antarctica
A silicified Todea trunk (Osmundaceae) from the Eocene of Patagonia
No full textThe Osmundaceae family is the sister group to all other extant leptosporangiate ferns. Its rich fossil record has enabled detailed reconstructions of the evolutionary history of the group. Fossil evidence for today’s Southern Hemisphere subtribe Todeinae, however, has been difcult to accumulate, with only two unambiguous fossil occurrences of modern Todea. Here, we describe a silicifed Todea stem from the Eocene Laguna del Hunco lagerstätte of Patagonia. The stem contains a heterogeneous outer cortex with distinct fbrous rings surrounding the leaf traces, indicative of subtribe Todeinae; nests of thick-walled fbres associated with departing leaf traces together with the sclerenchymatous pith and with abundant sclerenchyma fbres in the inner stipe cortex enable assignment to Todea. The stem difers from T. tidwellii—the only other known fossil Todea stem described thus far—mainly in lacking sclerenchyma lining the adaxial concavity of the stipe bundle. Co-occurrence with sterile foliage fragments indicates that the stem may belong to Todea amissa, a species that was initially described based on frond compressions from the same deposits. Our fnding corroborates the widely disjunct Gondwanan distribution of Todea across the Southern Hemisphere in the past, and provides an impetus to re-assess genetic divergence between the relictual African and Australasian populations of Todea barbara today in order to resolve the evolutionary history of the group more clearly. Finally, this frst report of structurally preserved plant remains from Laguna del Hunco highlights the thus far untapped potential for anatomical preservation in this important fossil lagerstätte.Fil: Bomfleur, Benjamin. Westfälische Wilhelms Universität; AlemaniaFil: Escapa, Ignacio Hernán. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Uncharted permian to jurassic continental deposits in the far north of victoria land, east antarctica
No full text© 2020 The Author(s). Published by The Geological Society of London. All rights reserved.The remote lower reaches of the Rennick Glacier in the far north of Victoria Land hold some of the least-explored outcrop areas of the Transantarctic basin system. Following recent international field-work efforts in the Helliwell Hills, we here provide a comprehensive emendation to the regional stratigraphy. Results of geological and palaeontological reconnaissance and of petrographic, geochemical and palynostratigraphic analyses reveal a stack of three previously unknown sedimentary units in the study area: the Lower Triassic Van der Hoeven Formation (new unit, 115+ m thick) consists mainly of quartzose sandstone and non-carbonaceous mudstone rich in continental trace fossils. The Middle to Upper Triassic Helliwell Formation (new unit, 235 m thick) consists of coal-bearing overbank deposits and volcaniclastic sandstone and yielded typical plant fossils of the Gondwanan Dicroidium flora together with plant-bearing silicified peat. The succession is capped by c. 14 m of the sandstone-dominated Section Peak Formation (uppermost Triassic–Lower Jurassic). Our results enable more detailed correlation of the Palaeozoic–Mesozoic successions throughout East Antarctica and into Tasmania. Of particular interest is one section that spans the end-Permian mass extinction interval, which promises to allow detailed reconstructions of high-latitude vegetation dynamics across this critical interval in Earth history.Y
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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