1,720,976 research outputs found
The Endocranial Cavities of Sloths (Xenarthra, Folivora): Insights from the Brain Endocast, Bony Labyrinth, and Cranial Sinuses
No full textFolivora (sloths) constitutes a taxonomically rich group comprised of many extinct representatives and a few living forms. The clade also shows remarkable skeletal disparity that has been studied by paleontologists for more than two centuries. Accordingly, the first published information on endocranial morphology in fossil sloths, recovered though natural or reconstructed internal casts or broken specimens, date to the nineteenth century. Today, new computed tomography (CT) and three-dimensional digital reconstruction techniques allow observation in great detail of many endocranial structures, such as the brain endocast and cranial nerve trajectories, as well as the bony labyrinth of the inner ear and patterns of cranial pneumatization. These analyses have been recently applied to modern (Bradypus and Choloepus) and extinct (Catonyx, Glossotherium, and Megatherium) sloth skulls. General patterns include a conservative brain anatomy among sloths, a strong phylogenetic imprint on the bony labyrinth, and the presence of extensive cranial pneumatization in some extinct mylodontids. The present work comprises a synthesis of both historical and recently published data on endocranial structures in Folivora. Further studies of the endocranial cavities in other extinct sloths have the potential to enhance understanding of several aspects of the clade’s evolutionary history, including phylogeny and paleobiology
A relative of the Ganges and Indus river dolphins from Miocene deposits of the Amazonian basin: multiple toothed whale invasions of freshwater environments?
Get PDFDuring their transition to the marine environment, in addition to numerous morphological changes, early
cetaceans had to evolve physiologically to face the excess of salt due to the ingestion of seawater. But
evolution is complex, far from being a process with one way. After this critical Eocene step of their
evolutionary history, followed by several phases of diversification of fully marine cetaceans (leading to the two
extant suborders, Mysticeti, the baleen whales, and Odontoceti, the toothed whales), members of several
odontocete clades independently recolonized freshwater environments. Nowadays, four species in the genera
Inia, Lipotes (possibly recently extinct), and Platanista (two species), exclusively occupy river and lake habitats,
respectively in the Amazon-Orinoco, Yangtse, and Ganges-Indus river basins. Based on morphological and
molecular data, as well as on paleontological information on their fossil relatives, it has been demonstrated
that Inia, Lipotes, and Platanista are relict members of ancient lineages with distantly related marine
ancestors.
Among them, the endangered Platanista is interesting for several reasons. In addition to its unusual cranial
morphology, this nearly blind dolphin is the sole survivor of the superfamily Platanistoidea, much diversified
from the late Oligocene up to the middle Miocene. Among platanistoids, the fossil record of Platanistidae is
dominated by members of the extinct subfamily Pomatodelphininae, most of them discovered in marine to
estuarine Miocene layers. Only one fragmentary mandible, from marine deposits of the early Miocene of
Oregon, has been tentatively referred to the subfamily Platanistinae, the clade typified by the extant
Platanista.
We report on the discovery of an isolated platanistid periotic (ear bone, one of the most diagnostic elements
in crown cetaceans) found in late middle Miocene sediments of the Fitzcarrald Arch area, Peruvian Amazonia.
This periotic is identified as belonging to a platanistine, based on several derived characters shared with
Platanista. Even if fragmentary, this is likely the most significant fossil record of a platanistine, partly filling the
temporal gap between the emergence of the subfamily and the Recent Platanista. Interestingly, this specimen
was found in a geographic area now occupied by Inia. Sedimentology and associated fauna indicate that this
middle Miocene depositional area corresponds to an inland tidally-influenced freshwater/oligohaline basin.
Although a marine origin cannot be discarded for this new fossil platanistine record, it is tempting to
hypothesize that it illustrates an early step of the colonization of a freshwater habitat, in a region very far from
the area of Platanista. If confirmed, this interpretation would further support the scenario of multiple Miocene
freshwater invasions by members of several odontocete clades.
Reasons for such drastic ecological changes are not yet clear, and several factors, both biological (competition
with diversifying pelagic delphinoids, flight from oceanic predators, migration of prey in freshwater regions)
and physical (sea level changes and temperature fluctuation), might have played a role. Species of three
strictly freshwater odontocete genera survived until the Holocene, and one of them probably went extinct at
the dawn of a twenty-first century that will be decisive for the fate of the remaining others
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
