1,721,035 research outputs found
Dataset for article: Synchrotron radiation-based X-ray tomography reveals sexual dimorphism in cementum incrementation
No full textThis dataset supports the publication: Newham, Elis et al. (2020). Synchrotron radiation-based X-ray tomography reveals sexual dimorphism in cementum incrementation, Proceedings of the Royal Society: Interface </span
Exploring the use of tomography for the quantification of cementum growth patterns across the mammal phylogeny
No full textThis project is focused on the application of state-of-the-art imaging technologies and novel analytical techniques in order to improve understanding of the growth and structure of cementum; the mineralised tissue that connects teeth to the peridontium in mammals. Like all vertebrate hard tissues, the growth of cementum is controlled by a series of natural rhythms that control its pattern and pace. This is recorded in circum-annual increments (similar to tree rings) hypothetically created by dietary differences in the production rate of its two key components; hydroxyapatite matrix and collagen fibres. As cementum is only rarely resorbed, these increments can be counted to provide a direct estimate of chronological age, a technique known as cementochronology. Further, the circum-annual rhythm followed by cementum increments may also allow them to record discrete life history events that create severe strain on body metabolism over the course of several months, such as pregnancy. However, the exact causation and rhythm of cementum increments is still poorly understood due to a paucity of direct experimental study. The majority of previous studies of cementochronology have been based on thin-section histology, and several caveats of this approach have undermined confidence in the ability to quantitatively analyse cementum increments. Overall, current study of cementum lacks the application of modern technology and analytical methods that have revolutionised interpretation of microstructures and ultrastructures of other hard tissues such as bone, and increased their use as hallmarks of disease or as records of life history. The application of synchrotron X-ray tomography (SR CT) has here been used to improve understanding of the structure and count of cementum increments in mammals ranging from our oldest ancestors, to some of our closest relatives. The non-destructive nature and high throughput of SR CT has allowed study of large samples of Morganucodon and Kuehneotherium, two of the oldest known fossil mammals from the early Jurassic (~200 million years ago). The three-dimensional perspective and ultra-high resolutions (<500nm voxel size) of SR CT data provided an unprecedented level of detail to study and more precise counts of increments than previous thin-section-based techniques, which in-turn provided minimum estimates of maximum lifespan for both animals. Further, as the lifespans of modern mammals are inversely related to their basal metabolic rate and post-natal growth rate, these estimates have been used to improve understanding of the physiology of early mammals and the evolution of the sophisticated endothermic (warm-blooded) physiology of modern mammals. From this study the potential of SR CT for analyzing cementum growth, and the relationship between cementum growth and life history variables, was made clear. Subsequent SR CT imaging was conducted on a sample of rhesus macaque monkeys (Macaca mulatta), raised in laboratory conditions. One sub-sample consisted of breeding females, another of non-breeding females, as well as a juvenile female and a male. This sample was used to study the optimal experimental settings for SR CT imaging of cementum, and generate an image processing and analysis workflow to automatically count cementum increments and study their shape and texture using computer vision. This workflow was then used to study sexual dimorphism in increment structure, and to investigate the potential for pregnancy events to be recorded in SR CT cementum data in both the M. mulatta sample and samples of C12th and C19th century archaeological humans of known sex (including three C19th individuals of known age and reproductive history). Significant dimorphism in increment shape and texture was found in both taxa. Female increments were found to be significantly more tortuous than males, with lower contrast and less well defined boundaries. Further, increments formed during pregnancy were found to be more chaotic in shape and texture than surrounding increments. Finally, SR CT was used to image the cementum increments of a diverse fauna of fossil mammals from the Middle Jurassic of the UK (Bathonian: ~168-166 million years ago). This fauna can be split into stem mammals (mammaliaforms alongside Morganucodon and Kuehneotherium), and crown mammals (bracketed evolutionarily by living mammals). Using the automative counting technique developed for counting primate cementum increments, it was found that mammaliaforms lived significantly longer maximum lifespans than contemporary crown mammals. This in-turn suggests a proportional disparity in metabolic potential, and that Mid Jurassic crown mammals had developed a similar basal metabolic rate to living mammals of comparable body mass. In summary, the work presented in this thesis has shown that the application of state-of-the-art analysis techniques has the ability to maximise the potential of cementum as a recording structure of disparate elements of life history among mammals. The workflow for imaging, processing and study developed here can be applied to a wide range of life history variables, for both fossil and extant taxa. The automated nature of the image analysis techniques presented overcomes many of the major caveats highlighted in previous thin-section based studies of cementum and their applicability, robusticity and accuracy can only be improved by their continued development in the wider cementochronology community outside of this project
Data from: Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the K-Pg boundary
No full textIt is often postulated that mammalian diversity was suppressed during the Mesozoic Era and increased rapidly after the Cretaceous–Palaeogene (K–Pg) extinction event. We test this hypothesis by examining macroevolutionary patterns in early therian mammals, the group that gave rise to modern placentals and marsupials. We assess morphological disparity and dietary trends using morphometric analyses of lower molars, and we evaluate generic level taxonomic diversity patterns using techniques that account for sampling biases. In contrast with the suppression hypothesis, our results suggest that an ecomorphological diversification of therians began 10–20 Myr prior to the K–Pg extinction event, led by disparate metatherians and Eurasian faunas. This diversification is concurrent with ecomorphological radiations of multituberculate mammals and flowering plants, suggesting that mammals as a whole benefitted from the ecological rise of angiosperms. In further contrast with the suppression hypothesis, therian disparity decreased immediately after the K–Pg boundary, probably due to selective extinction against ecological specialists and metatherians. However, taxonomic diversity trends appear to have been decoupled from disparity patterns, remaining low in the Cretaceous and substantially increasing immediately after the K–Pg extinction event. The conflicting diversity and disparity patterns suggest that earliest Palaeocene extinction survivors, especially eutherian dietary generalists, underwent rapid taxonomic diversification without considerable morphological diversification.,Fossil occurrence datasetFossil occurrences of tribosphenidan mammals from the Cretaceous through Selandian. This dataset is modified from an occurrence list downloaded from the Paleobiology Database (www.paleobiodb.org) on November 19, 2015.Grossnickle&amp;Newham2016_FossilOccurrenceDataset.xlsxMolar landmark and outline coordinatesThese are the original point coordinates (in tps format) used in a geometric morphometric analysis of lower molar shape. For each genus, the first seven coordinates are cusp landmarks, the next 20 coordinates outline the talonid, and the final 20 coordinates outline the trigonid. (Note that the outline coordinates are not equally-spaced semilandmarks.) See Grossnickle &amp; Newham (2016) for information concerning how these coordinates were analyzed.molar_LM_coords_GrossnickleNewham2016.xlsx</span
Data from: Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the K-Pg boundary
No full textIt is often postulated that mammalian diversity was suppressed during the Mesozoic Era and increased rapidly after the Cretaceous–Palaeogene (K–Pg) extinction event. We test this hypothesis by examining macroevolutionary patterns in early therian mammals, the group that gave rise to modern placentals and marsupials. We assess morphological disparity and dietary trends using morphometric analyses of lower molars, and we evaluate generic level taxonomic diversity patterns using techniques that account for sampling biases. In contrast with the suppression hypothesis, our results suggest that an ecomorphological diversification of therians began 10–20 Myr prior to the K–Pg extinction event, led by disparate metatherians and Eurasian faunas. This diversification is concurrent with ecomorphological radiations of multituberculate mammals and flowering plants, suggesting that mammals as a whole benefitted from the ecological rise of angiosperms. In further contrast with the suppression hypothesis, therian disparity decreased immediately after the K–Pg boundary, probably due to selective extinction against ecological specialists and metatherians. However, taxonomic diversity trends appear to have been decoupled from disparity patterns, remaining low in the Cretaceous and substantially increasing immediately after the K–Pg extinction event. The conflicting diversity and disparity patterns suggest that earliest Palaeocene extinction survivors, especially eutherian dietary generalists, underwent rapid taxonomic diversification without considerable morphological diversification
Complex neuroanatomy in the rostrum of the Isle of Wight theropod <em>Neovenator salerii</em>
No full textThe discovery of large, complex, internal canals within the rostra of fossil reptiles has been linked with an enhanced tactile function utilised in an aquatic context, so far in pliosaurids, the Cretaceous theropod Spinosaurus, and the related spinosaurid Baryonyx. Here, we report the presence of a complex network of large, laterally situated, anastomosing channels, discovered via micro-focus computed tomography (μCT), in the premaxilla and maxilla of Neovenator, a mid-sized allosauroid theropod from the Early Cretaceous of the UK. We identify these channels as neurovascular canals, that include parts of the trigeminal nerve; many branches of this complex terminate on the external surfaces of the premaxilla and maxilla where they are associated with foramina. Neovenator is universally regarded as a ‘typical’ terrestrial, predatory theropod, and there are no indications that it was aquatic, amphibious, or unusual with respect to the ecology or behaviour predicted for allosauroids. Accordingly, we propose that enlarged neurovascular facial canals shouldn’t be used to exclusively support a model of aquatic foraging in theropods and argue instead that an enhanced degree of facial sensitivity may have been linked with any number of alternative behavioural adaptations, among them defleshing behaviour, nest selection/maintenance or social interaction
Dataset for: Reptile-like physiology in Early Jurassic stem mammals
Full text linkDataset supports: Newham, E. et al. (2020). Reptile-like physiology in Early Jurassic stem-mammals. Nature Communications.
Virtual thin sections through tooth roots of Jurassic mammals, showing cementum increments.</span
Dataset for: A robust, semi-automated approach for counting cementum increments imaged with X-ray computed tomography
No full textData of manuscript A robust, semi-automated approach for counting cementum increments imaged with X-ray computed tomography in PloS One.</span
Synchrotron radiation-based X-ray tomography reveals life history in primate cementum incrementation
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