1,721,172 research outputs found
Unusual gut contents in a Cretaceous ichthyosaur
No full textBenjamin P. Kear, Walter E. Boles and Elizabeth T. Smit
Evolution of hind limb proportions in kangaroos (Marsupialia: macropodoidea)
No full textBenjamin P. Kear, Michael S. Y. Less, Wayne R. Gerdtz and Timothy F. Flanneryhttp://librariesaustralia.nla.gov.au.proxy.library.adelaide.edu.au/apps/kss?action=Search&mode=display&queryid=8&asyncsupported=tru
Reassessment of the <i>Styxosaurus snowii</i> (Williston, 1890) holotype specimen and its implications for elasmosaurid plesiosaurian interrelationships
No full textThe holotype (KUVP 1301) of Styxosaurus snowii—one of the earliest described elasmosaurid plesiosaurians—consists of a well-preserved cranium, mandible and articulated sequence of anterior–mid-series cervical vertebrae found in the lowermost Campanian strata of the Smoky Hill Chalk Member in the Niobrara Formation of Kansas, USA. This particular specimen has proven important for recent phylogenies of Elasmosauridae, and is integral to resulting definitions of the subfamily-level clade, Styxosaurinae. Despite this, KUVP 1301 has not been redescribed or figured in detail since its original taxonomic establishment. We, therefore, re-evaluated KUVP 1301 and assessed its phylogenetic implications. Several notable character states are pertinent for diagnosing S. snowii at genus and species level: (1) an anisodont functional dentition comprising enlarged premaxillary and dentary teeth with a pair of maxillary ‘fangs’, and elongate posterior-most dentary teeth that overlap the upper tooth row; (2) a prominent dorsomedian crest extending from the tip of the premaxillary rostrum, and expanding into a low ‘mound-like’ boss between the external bony nasal openings and orbits; (3) a pronounced convex projection on the posterolateral edge of the squamosals; and (4) platycoelous post-axial cervical vertebral centra that are substantially longer than high, and bear both lateral longitudinal ridges and ventral notches. Character state comparisons with the congeneric subfamily specifier Styxosaurus browni suggest that taxonomic distinction is possible, but equivocal. We, therefore, restrict our definition of Styxosaurus to morphologies observable in KUVP 1301. Furthermore, phylogenetic analysis of our first-hand data returns inconsistent elasmosaurid intra-clade relationships, especially with regard to Styxosaurinae. Consequently, we posit that a more targeted reassessment of Elasmosauridae is necessary to resolve both species-level topologies and higher taxonomy within the group. Sven Sachs* [[email protected]] Naturkunde-Museum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602 Bielefeld, Germany; Johan Lindgren [[email protected]], Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden; Benjamin P. Kear [[email protected]] Museum of Evolution, Uppsala University, Norbyvägen 16, Uppsala SE-752 36, Sweden. *Also affiliated with: Im Hof 9, 51766 Engelskirchen, Germany. Received 26.5.2016; revised 13.7.2018; accepted 24.7.2018.</p
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
Myth of the <i>QANTAS</i> leap: perspectives on the evolution of kangaroo locomotion
No full textThe distinctive QANTAS ‘flying kangaroo’ motif of Australia’s national airline signifies what many people regard as the pinnacle of kangaroo evolution—a large-bodied marsupial specialized for endurance-hopping. However, while almost all extant macropodoids (the crown group including kangaroos) use hopping gaits to some extent, the fossil record reveals that the locomotory capabilities of extinct macropodoids were comparatively diverse. The earliest recognized Oligocene–middle Miocene macropodoids probably employed quadrupedal bounding, climbing and slower speed hopping as their primary modes of locomotion. Yet, all were apparently small-bodied (20 kg) forms not appearing until the late Miocene coincident with increasing aridity and the spread of openly vegetated habitats. Hopping is functionally problematic at larger body sizes. Consequently, the later radiation of macropodids (kangaroos, wallabies and their relatives) achieved an optimal mass for efficient higher-speed hopping at ∼35 kg, with a theorized extreme limit of ∼140–160 kg. Modern kangaroos otherwise approach the peak mass range for such gaits at ∼50–90 kg, with the gigantic Pliocene–Pleistocene species of Protemnodon (‘giant wallabies’) at ∼100–160 kg likely being predominantly quadrupedal, and sthenurines (short-faced kangaroos) at ∼50–250 kg seemingly using bipedal striding. Here, we review the fossil evidence of macropodoid locomotion over the last ∼25 million years, and present preliminary analyses of limb bone and tarsal metric data. These indicate that the higher-speed endurance-hopping typical of modern large-bodied kangaroos was probably rare or absent in all but a few crown macropodoid lineages. The intrinsic gait variability of macropodoids has therefore diminished with Late Pleistocene megafaunal extinctions. As a result, the famous QANTAS ‘flying kangaroo’ actually depicts only one of what was once many successful locomotory strategies employed by macropodoids to conquer a range of terrestrial and arboreal habitats. Christine M. Janis [[email protected]], Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK; Adrian M. O’Driscoll [[email protected]], Centre for Anatomical and Human Studies, Hull York Medical School, University of York, York YO1O 5DD, UK; Benjamin P. Kear [[email protected]], The Museum of Evolution, Uppsala University, Norbyvägen 16, Uppsala SE-75236, Sweden.</p
- …
