1,720,962 research outputs found
Cymbospondylus Leidy 1868
No full textCymbospondylus Leidy, 1868 (14) Type species Cymbospondylus piscosus Leidy, 1868 (14) Referred species Cymbospondylus petrinus Leidy, 1868 (14); Cymbospondylus buchseri (15); Cymbospondylus nichollsi (16); *Corresponding author. Email: [email protected] (P.M.S.); [email protected] (E.M.G.); [email protected] (L.S.) Cymbospondylus duelferi (17); Cymbospondylus youngorum sp. nov. Genus diagnosis For a recent detailed diagnosis of the genus, see (17). In addition, the results of the phylogenetic analysis in this study offer an apomorphy-based diagnosis.Published as part of Sander, P. Martin, Griebeler, Eva Maria, Klein, Nicole, Juarbe, Jorge Velez, Wintrich, Tanja, Revell, Liam J. & Schmitz, Lars, 2021, Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans, pp. 1-15 in Science (New York, N. Y.) (New York, N. Y.) 374 (6575) on pages 1-2, DOI: 10.1126/science.abf5787, http://zenodo.org/record/580532
Fig. 6 in Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans
No full textFig. 6. The adaptive landscape of body-size evolution. (A and B) Ichthyosaurs (A) feature two early adaptive shifts toward larger skull length, whereas cetaceans (B) entered selective regimes that promoted larger skull width much later in their evolution.Published as part of Sander, P. Martin, Griebeler, Eva Maria, Klein, Nicole, Juarbe, Jorge Velez, Wintrich, Tanja, Revell, Liam J. & Schmitz, Lars, 2021, Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans, pp. 1-15 in Science (New York, N.Y.) 374 (6575) on page 6, DOI: 10.1126/science.abf5787, http://zenodo.org/record/580532
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
The plesiosaur: remarkable morphology, histology, and physiology
Full text linkIn this dissertation, contributions to understanding the morphology, histology, and physiology of plesiosaurs, a major group of marine reptiles from the Age of Dinosaurs, are presented. By using comparative methods and new investigations on recent and fossil taxa, new insights of general importance for amniotes (true land animals) are developed. Furthermore, the results demonstrate the potential of interdisciplinary research, combining conventional vertebrate paleontological approaches, human anatomy, developmental biology, and medical biomechanics.
Plesiosaurs are one of the first described vertebrate fossils and raised many questions over the last 300 years in vertebrate paleontology. However, from the beginnings of paleontology as a science, it was also believed that plesiosaurs evolved in the Early Jurassic, and only few studies discussed a Triassic radiation. After an extraordinary discovery in a German clay pit near Warburg in North Rhine-Westphalia, the first Triassic plesiosaur was found and described in this thesis. The nearly complete and articulated skeleton of Rhaeticosaurus mertensi showed that already in the Triassic the plesiosaur body plan, unique histology, and physiology had evolved. This means that the evolution of plesiosaurs took place in the Triassic and furthermore, that plesiosaurs crossed the Triassic-Jurassic boundary, surviving the end-Triassic extinction event, unlike several other marine and terrestrial tetrapod groups.
In general, plesiosaurs show two major body plans, the plesiosauromorph body plan and the pliosauromorph body plan. The main difference between the two is that plesiosauromorphs have a small head and a long neck (up to 76 cervical vertebrae) and the pliosauromorphs have a huge head and a short neck. However, both body plans evolved convergently in different lineages in Plesiosauria. Nevertheless, the basal condition is a small head and a relative long neck built up by a high number of cervical vertebrae compared to the ancestor.
Plesiosaur cervical vertebrae, independently of taxon, show a special character: two large and symmetrical foramina piercing the ventral surface of the centra. These foramina are here renamed “intersegmental artery foramina” because they do not represent nutrient foramina, as previously believed, but the entry of intersegmental arteries. Retention of these arteries is a strongly paedomorphic character because intersegmental arteries are an embryonic feature that is normally resorbed in a very early ontogenetic stage during the process of resegmentation. μCt investigations and comparison to the development in modern amniotes showed that plesiosaurs did not resorb the arteries during the resegmentation process. The reason is not understood, but it is probably linked to the fact that the plesiosaur count of cervical vertebrae is the highest seen among all amniotes, suggesting that the processes involved in cervical vertebra development must have been faster than in any other amniote group.
However, not only the intervertebral artery foramina raise intriguing questions but also the function and mobility of the long neck of plesiosauromorphs, which had been the subject of many studies. The plesiosaur neck, even in those taxa where it is longest relative to the body length, surprisingly is quite immobile. The neural spine of the cervical vertebrae is high, the zygapophyses are medially inclined, and the distance between the segments is very small. All of these features in the end must have resulted in an only slightly mobile neck. Hence, the mobility of the neck was tested in this thesis using an innovative approach from human anatomy, finite element modeling. The model indicates very limited mobility of only a few degrees in the intervertebral joint, allowing for the calculation of the total mobility of the neck of less than 180º.
Nevertheless, the long, immobile neck must have been useful. Plesiosaurs, especially the plesiosauromorph forms with the small head and the long neck, were hunting in school of fish. Fish in general are very sensitive to hydrodynamic waves. The small head and the long neck caused a hydrodynamic and optical camouflage effect, preventing the fish or school of fish from recognizing the plesiosaur as a large predator. This would have been the case if the plesiosaur would have had a shorter neck but also a small head. The long neck in plesiosaurs thus represent, a special adaptation to prey acquisition in the aquatic environment.
The studies on the plesiosaur neck led to the formulation of the hypothesis that the intervertebral joints in plesiosaurs and some other fossil reptiles had a proper intervertebral disc (IVD) in the dorsal vertebral column, similar to the IVD of mammals. To test this hypothesis, a comprehensive sample of amniote dorsal vertebrae, fossil and extant, was acquired. Particular emphasis was placed on articulated segments of vertebral columns from black shales. Morphology of the centrum, histology of the articular surface, and preserved soft tissues, such as different kinds of cartilage, confirm that the IVD is not only restricted to mammals.
Ancestral character state reconstruction showed that the IVD evolved convergently at least twice in the phylogeny of amniotes, once in synapsids and once in diapsids, but possibly more often. Furthermore, the reptile synovial joint (of recent snakes and crocodiles) shows also convergent evolution, which had been mentioned briefly in different studies but not shown comprehensively. In general, we see here that the evolution and development of the amniote axial skeleton follows similar rules, independently of whether it is from a mammal or a reptile
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
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
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