1,582 research outputs found
Internal cranial anatomy of Early Triassic species of â Saurichthys (Actinopterygii: â Saurichthyiformes): implications for the phylogenetic placement of â saurichthyiforms
A New Large â Pachycormiform (Teleosteomorpha: â Pachycormiformes) from the Lower Jurassic of Germany, with Affinities to the Suspension-Feeding Clade, and Comments on the Gastrointestinal Anatomy of Pachycormid Fishes
Pachycormiformes is a diverse clade of stem-teleost actinopterygian fishes with a stratigraphic range from the Lower Jurassic (Toarcian) to Upper Cretaceous (Maastrichtian). The Toarcian Posidonienschiefer Formation in SW Germany records the earliest occurrence of â Pachycormiformes in the fossil record, offering unique and crucial insight into the cladeâs origins and early adaptive radiation in the Early Jurassic. However, Early Jurassic taxa remain poorly studied with the taxonomic diversity and stratigraphic/geographic distributions insufficiently defined, thus masking the early part of this evolutionary radiation. Here, we report a new genus and species of pachycormid fish from the Posidonienschiefer Formation identified by phylogenetic analysis as falling in an intermediate position between Saurostomus and Ohmdenia at the base of the suspension-feeding clade. The new taxon shows a unique suite of cranial and postcranial characters. Several synapomorphies of the suspension-feeding clade, notably, the morphology of the hyomandibula, elongation of the skull, and reduced squamation are shared with the new taxon. The intestinal tract is exceptionally preserved, providing one of the most complete examples of pachycormid gastric anatomy. A comparison of the gastrointestinal anatomy of the new genus with other pachycormiforms indicates extensive taxonomic variation within the clade, in the configuration of both the midgut and spiral valve, potentially related to trophic divergence. The results highlight an underestimated high diversity and the rapid acquisition of trophic specializations in Pachycormiformes much earlier in the cladeâs evolution than previously considered
Morphology and phylogenetic relationships of fossil snake mackerels and cutlassfishes (Trichiuroidea) from the Eocene (Ypresian) London Clay Formation
âGempylidsâ (snake mackerels) and trichiurids (cutlassfishes) are pelagic fishes characterized by slender to eelâlike bodies, deepâsea predatory ecologies, and large fangâlike teeth. Several hypotheses of relationships between these groups have been proposed, but a consensus remains elusive. Fossils attributed to âgempylidsâ and trichiurids consist almost exclusively of highly compressed body fossils and isolated teeth and otoliths. We use microâcomputed tomography to redescribe two threeâdimensional crania, historically assigned to â Eutrichiurides winkleri and â Progempylus edwardsi, as well as an isolated braincase (NHMUK PV OR 41318). All from the London Clay Formation (Eocene, Ypresian), these specimens represent some of the oldest fossils identified as trichiuroids. We find that â Eutrichiurides winkleri does not show diagnostic characters of â Eutrichiurides, and it is assigned to a new genus. To investigate the placement of these fossils relative to extant lineages, we combine existing morphological character sets for âgempylidsâ and trichiurids along with published mitogenomic data. Our analyses recover a monophyletic Trichiuridae nested within a paraphyletic âGempylidaeâ. The taxon formerly known as â Eutrichiurides winkleri is considered Trichiuroidea incertae sedis, while â Progempylus edwardsi and NHMUK PV OR 41318 are recovered within the âgempylidâ grade. Using previously published descriptions and character optimizations from our phylogenetic analyses we suggest possible placements for laterally compressed body fossils assigned to Trichiuroidea (â Argestichthys, â Abadzekhia, â Chelifichthys, â Anenchelum, â Eutrichiurides, â Musculopedunculus).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146609/1/spp21221.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146609/2/spp21221_am.pd
A giant dapediid from the Late Triassic of Switzerland and insights into neopterygian phylogeny
A new Triassic neopterygian is described on the basis of a large three-dimensional neurocranium from the Rhaetian (Late Triassic) of the Kössen Formation (Schesaplana, Grisons, Switzerland). CT scanning reveals neurocranial features similar to Dapedium, suggesting that this new genus, Scopulipiscis saxciput gen. et sp. nov., was deep-bodied and potentially durophagous, although no associated dental material is known. An expanded phylogenetic analysis of actinopterygians resolves Dapediidae as a clade (inclusive of Tetragonolepis), although fails to recover any characters supporting the monophyly of the genus Dapedium. Dapediids are resolved as stem holosteans, filling a conspicuous gap in early neopterygian relationships. Pycnodonts, previously suggested as either stem teleosts or the sister group to dapediids, are resolved as a clade on the neopterygian stem. Similarities between the new taxon described here and Dapedium provide insights into morphological disparity within early members of the groupâsuggesting that the ecological expansion of dapediids originated prior to the End-Triassic extinctionâas well as contributing to a growing understanding of endocranial anatomy in Palaeozoic and Early Mesozoic actinopterygians
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Reconceptualizing the Politics of Pockets of Effectiveness: A Power Domains Approach
This previous chapter argued that existing studies of PoEs have struggled to specify the forms of politics that shape how PoEs emerge and perform PoEs over time. To help address this problem, this chapter outlines the new conceptual and methodological approach developed for this project, which constitutes the first systematic investigation of PoEs across different types of political context. In conceptual terms, the authors argue that an alignment of political settlements analysis with critical theories of state power and African politics can help reveal how PoEs are shaped by underlying relations of power and politics. However, PoEs also need to be located within the particular âpolicy domainâ that they operate within, and which defines the political role they play, the policy challenges they face, and the organizational characteristics they require to perform effectively. The chapter identifies how this integrated âpower domainsâ approach can generate researchable propositions and how these were investigated through a mixture of within- and across-case analysis. It summarizes the results of the expert surveys that undertaken in Ghana, Kenya, Rwanda, Uganda, and Zambia, which were chosen to represent different types of political settlement. These surveys identified state agencies that operated within the domain of economic governance, namely ministries of finance, central banks, and revenue authorities. The chapter discusses how in-depth mixed methods investigations of these fifteen organizational case-studies were undertaken, tracking performance from the early 1990s through to the late 2010s, and locating each within shifting political settlement dynamics and the changing transnational political economy of development
A Late Devonian actinopterygian suggests high lineage survivorship across the end-Devonian mass extinction
LAB-AID: an interactive web application for visualization of multi-level data from biological experiments
A key step in understanding the results of biological experiments is visualization of the data. Many laboratory experiments contain a range of measurements that exist within a hierarchy of interdependence. An automated and facile way to visualize and interrogate such multi-level data, across many experimental variables, would: 1) lead to improved understanding of the results, 2) help to avoid misleading interpretation of statistics, and 3) easily identify outliers and sources of batch and confounding effects. While many excellent graphing solutions already exist, they are often geared towards the production of publication-ready plots, the analysis of a single variable at a time, require programming expertise, or are unnecessarily complex for the task at hand. Here we present LAB-AID (Laboratory Automated Interrogation of Data), an interactive tool specifically designed to automatically visualize and query hierarchical data resulting from biological experiment
Measuring well-being in sport performers: where are we now and how do we progress?
The importance of optimal well-being and mental health in elite athletes has received increasing attention and debate in
both the academic and public discourse. Despite the number of challenges and risk factors for mental health and well-being
recognised within the performance lifestyle of elite athletes, the evidence base for intervention is limited by a number of
methodological and conceptual issues. Notably, there exists an increasing emphasis on the development of appropriate sportspecifc measures of athlete well-being, which are required to underpin strategies targeted at the protection and enhancement
of psychosocial functioning. Therefore, the purpose of this article is to review psychometric issues in well-being research and
discuss the implications for the measurement of well-being in sport psychology research. Drawing on the broader literature
in related disciplines of psychology, the narrative discusses four key areas in the scale development process: conceptual and
theoretical issues, item development issues, measurement and scoring issues, and analytical and statistical issues. To conclude,
a summary of the key implications for sport psychology researchers seeking to develop a measure of well-being is presented
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