976 research outputs found
Dynamics of dental evolution in ornithopod dinosaurs.
Ornithopods were key herbivorous dinosaurs in Mesozoic terrestrial ecosystems, with a variety of tooth morphologies. Several clades, especially the 'duck-billed' hadrosaurids, became hugely diverse and abundant almost worldwide. Yet their evolutionary dynamics have been disputed, particularly whether they diversified in response to events in plant evolution. Here we focus on their remarkable dietary adaptations, using tooth and jaw characters to examine changes in dental disparity and evolutionary rate. Ornithopods explored different areas of dental morphospace throughout their evolution, showing a long-term expansion. There were four major evolutionary rate increases, the first among basal iguanodontians in the Middle-Late Jurassic, and the three others among the Hadrosauridae, above and below the split of their two major clades, in the middle of the Late Cretaceous. These evolutionary bursts do not correspond to times of plant diversification, including the radiation of the flowering plants, and suggest that dental innovation rather than coevolution with major plant clades was a major driver in ornithopod evolution
On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna)
The history of discovery and interpretation of several dinosaurs collected from quarries near the town of Hastings during the latter half of the 19th century is more complicated than it should be. Samuel Husbands Beckles and Charles Dawson collected several large ornithopod skeletons from this area, but just a few bones from these skeletons were subsequently described and interpreted (principally) by Richard Owen and Richard Lydekker. All these specimens merited recognition because they had the potential to contribute to an on-going debate about the anatomical structure and relationships of the iconic Wealden dinosaur Iguanodon. Unfortunately, no detailed description of these important skeletons was published in later years. Furthermore, previously known associations of bones and even provenance information, linked to the specimens that were gradually acquired by the Natural History Museum, are unclear. Confusion may have arisen because Richard Lydekker used the private collector Charles Dawson as a voluntary curatorial assistant. This account documents the past work on the osteology of material that can be attributed to Hypselospinus fittoni. Nearly all such material is described here for the first time, and every effort has been made to re-establish associations between bones as well as provenance information. A skeletal reconstruction of Hypselospinus is attempted on the basis of the hypodigm. Most of the on-going confusion concerning the affinity of this material with either Hy. fittoni or its sympatric contemporary Barilium dawsoni has been resolved. Hypselospinus fittoni (Lydekker, 1889) is rediagnosed on the basis of this new and relatively comprehensive anatomical description, and this animal is compared with known contemporary and closely related taxa. Some recently published accounts claiming to be revisions of the taxonomy of Wealden ‘iguanodonts’, including material belonging to the hypodigm of Hy. fittoni, have failed to adhere to basic taxonomic principles and have caused more confusion than was strictly necessary. The systematic position of Hypselospinus is reassessed cladistically. The cladistic analysis forms the basis for a revised hierarchical classification of derived ornithopods. The consensus topology generated by the systematic analysis has been used to explore the phylogenetic history of these dinosaurs and create an internally consistent classificatory hierarchy (phylogenetic definitions and Linnaean diagnoses are given for critical positions in the topology). This analysis suggests that there is a fundamental split amongst the more derived (clypeodontan) ornithopod ornithischians into the clades Hypsilophodontia and Iguanodontia. There is evidence for anatomical parallelism and convergence (homoplasy) particularly between large-bodied representatives of both clades. Hypselospinus is one of the earliest known styracosternan iguanodontians and displays anatomical characteristics that presage the evolution of the extraordinarily abundant and diverse hadrosaurs of the latest Cretaceous (Campanian−Maastrichtian). These observations cast fresh light on the phylogeny, classification, diversity, and biology of derived ornithopods. There is little doubt that Hy. fittoni could have been understood far better more than a century ago. That this statement is undoubtedly true is reflected in the century of doubt and confusion that has surrounded this taxon and its original incarnation as Iguanodon fittoni.This is the accepted manuscript of a paper published in the Zoological Journal of the Linnean Society (Norman, D. B. (2015), On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna). Zoological Journal of the Linnean Society, 173: 92–189. doi: 10.1111/zoj.12193). The final version is available at http://dx.doi.org/10.1111/zoj.1219
Childbearing intentions in a low fertility context: the case of Romania
This paper applies the Theory of Planned Behaviour (TPB) to find out the predictors of fertility intentions in Romania, a low-fertility country. We analyse how attitudes, subjective norms and perceived behavioural control relate to the intention to have a child among childless individuals and one-child parents. Principal axis factor analysis confirms which items proposed by the Generation and Gender Survey (GGS 2005) act as valid and reliable measures of the suggested theoretical socio-psychological factors. Four parity-specific logistic regression models are applied to evaluate the relationship between the socio-psychological factors and childbearing intentions. Social pressure emerges as the most important aspect in fertility decision-making among childless individuals and one-child parents, and positive attitudes towards childbearing are a strong component in planning for a child. This paper also underlines the importance of the region-specific factors when studying childbearing intentions: planning for the second child significantly differs among the development regions, representing the cultural and socio-economic divisions of the Romanian territory
Age-related changes in global motion coherence: conflicting haemodynamic and perceptual responses
Our aim was to use both behavioural and neuroimaging data to identify indicators of perceptual decline in motion processing. We employed a global motion coherence task and functional Near Infrared Spectroscopy (fNIRS). Healthy adults (n = 72, 18-85) were recruited into the following groups: young (n = 28, mean age = 28), middle-aged (n = 22, mean age = 50), and older adults (n = 23, mean age = 70). Participants were assessed on their motion coherence thresholds at 3 different speeds using a psychophysical design. As expected, we report age group differences in motion processing as demonstrated by higher motion coherence thresholds in older adults. Crucially, we add correlational data showing that global motion perception declines linearly as a function of age. The associated fNIRS recordings provide a clear physiological correlate of global motion perception. The crux of this study lies in the robust linear correlation between age and haemodynamic response for both measures of oxygenation. We hypothesise that there is an increase in neural recruitment, necessitating an increase in metabolic need and blood flow, which presents as a higher oxygenated haemoglobin response. We report age-related changes in motion perception with poorer behavioural performance (high motion coherence thresholds) associated with an increased haemodynamic response
Garden and landscape-scale correlates of moths of differing conservation status: significant effects of urbanization and habitat diversity
Moths are abundant and ubiquitous in vegetated terrestrial environments and are pollinators, important herbivores of wild plants, and food for birds, bats and rodents. In recent years, many once abundant and widespread species have shown sharp declines that have been cited by some as indicative of a widespread insect biodiversity crisis. Likely causes of these declines include agricultural intensification, light pollution, climate change, and urbanization; however, the real underlying cause(s) is still open to conjecture. We used data collected from the citizen science Garden Moth Scheme (GMS) to explore the spatial association between the abundance of 195 widespread British species of moth, and garden habitat and landscape features, to see if spatial habitat and landscape associations varied for species of differing conservation status. We found that associations with habitat and landscape composition were species-specific, but that there were consistent trends in species richness and total moth abundance. Gardens with more diverse and extensive microhabitats were associated with higher species richness and moth abundance; gardens near to the coast were associated with higher richness and moth abundance; and gardens in more urbanized locations were associated with lower species richness and moth abundance. The same trends were also found for species classified as increasing, declining and vulnerable under IUCN (World Conservation Union) criteria
Quantitative cross-species extrapolation between humans and fish: The case of the anti-depressant fluoxetine
This article has been made available through the Brunel Open Access Publishing Fund.Fish are an important model for the pharmacological and toxicological characterization of human pharmaceuticals in drug discovery, drug safety assessment and environmental toxicology. However, do fish respond to pharmaceuticals as humans do? To address this question, we provide a novel quantitative cross-species extrapolation approach (qCSE) based on the hypothesis that similar plasma concentrations of pharmaceuticals cause comparable target-mediated effects in both humans and fish at similar level of biological organization (Read-Across Hypothesis). To validate this hypothesis, the behavioural effects of the anti-depressant drug fluoxetine on the fish model fathead minnow (Pimephales promelas) were used as test case. Fish were exposed for 28 days to a range of measured water concentrations of fluoxetine (0.1, 1.0, 8.0, 16, 32, 64 μg/L) to produce plasma concentrations below, equal and above the range of Human Therapeutic Plasma Concentrations (HTPCs). Fluoxetine and its metabolite, norfluoxetine, were quantified in the plasma of individual fish and linked to behavioural anxiety-related endpoints. The minimum drug plasma concentrations that elicited anxiolytic responses in fish were above the upper value of the HTPC range, whereas no effects were observed at plasma concentrations below the HTPCs. In vivo metabolism of fluoxetine in humans and fish was similar, and displayed bi-phasic concentration-dependent kinetics driven by the auto-inhibitory dynamics and saturation of the enzymes that convert fluoxetine into norfluoxetine. The sensitivity of fish to fluoxetine was not so dissimilar from that of patients affected by general anxiety disorders. These results represent the first direct evidence of measured internal dose response effect of a pharmaceutical in fish, hence validating the Read-Across hypothesis applied to fluoxetine. Overall, this study demonstrates that the qCSE approach, anchored to internal drug concentrations, is a powerful tool to guide the assessment of the sensitivity of fish to pharmaceuticals, and strengthens the translational power of the cross-species extrapolation
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
Phylogeny of Basal Iguanodonts (Dinosauria: Ornithischia): An Update
The precise phylogenetic relationships of many non-hadrosaurid members of Iguanodontia, i.e., basal iguanodonts, have been unclear. Therefore, to investigate the global phylogeny of basal iguanodonts a comprehensive data matrix was assembled, including nearly every valid taxon of basal iguanodont. The matrix was analyzed in the program TNT, and the maximum agreement subtree of the resulting most parsimonious trees was then calculated in PAUP. Ordering certain multistate characters and omitting taxa through safe taxonomic reduction did not markedly improve resolution. The results provide some new information on the phylogeny of basal iguanodonts, pertaining especially to obscure or recently described taxa, and support some recent taxonomic revisions, such as the splitting of traditional “Camptosaurus” and “Iguanodon”. The maximum agreement subtree also shows a close relationship between the Asian Probactrosaurus gobiensis and the North American Eolambia, supporting the previous hypothesis of faunal interchange between Asia and North America in the early Late Cretaceous. Nevertheless, the phylogenetic relationships of many basal iguanodonts remain ambiguous due to the high number of taxa removed from the maximum agreement subtree and poor resolution of consensus trees
The Postcranial Skeleton of an Exceptionally Complete Individual of the Plated Dinosaur Stegosaurus stenops (Dinosauria: Thyreophora) from the Upper Jurassic Morrison Formation of Wyoming, U.S.A.
Copyright: © 2015 Maidment et al. This is an open access article distributed under the terms of the Creative Commons Attribution License [4.0], which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article
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