Understanding the feeding mechanisms and diet of ornithopod dinosaurs is fundamental to understanding their role in Late Cretaceous ecosystems. Current hypotheses of feeding behaviour are based on functional morphology, and testing these is problematic. Microscopic scratches, microwear, that form on teeth in vivo during feeding are known to record the relative movement of the tooth rows and to capture evidence of tooth-food interactions; however, their applicability to ornithischian dinosaurs has not been tested. The development of a fast non-abrasive and residue free method for the removal of resistant consolidant, along with a safe, rapid technique for replicating tooth surfaces was the first step towards assessing the suitability of quantitative tooth microwear analysis techniques for dinosaur teeth. An evaluation of appropriate statistical analysis methods followed, identifying suitably stringent tests for the analysis of variance in the multi-modal directional microwear data. Analysis of microwear orientation in Iguana iguana provided direct evidence for relative motion of the jaws. Microwear from the basal ornithischian Lesothosaurus diagnosticus revealed three distinct sets of scratches in different orientations that were comparable to those of I. iguana, confirming the isognathic, near-vertical, simple adduction predicted for this dinosaur. Results from the basal ornithopod Hypsilophodon foxii indicate a propalinal translation of the lower jaw during feeding and provide strong support for muscular cheeks, whilst those from the hadrosaurid Edmontosaurus indicate a near-vertical posterodorsal power stroke with a secondary propalinal action and support the presence of a pleurokinetic hinge. Analysis of a range of hadrosaurid taxa found that three differing mastication methods existed, potentially diet related. Furthermore, microwear suggests that here is no significant difference in the jaw mechanics between iguanodontians and hadrosaurids. The results demonstrate that microwear has great potential for unravelling the mystery of dinosaur feeding and identifying key stages in the evolution of jaw mechanics in ornithopods.

The preservation of algal remains and their stratigraphy in recent lake sediments is examined in relation to documented fluctuations in the composition and abundance of the phytoplankton in the same lakes. Identifiable remains of non-siliceous algae were commonly recovered, but the degree of preservation varied specifically and between lakes. Smaller species were under-represented owing to rapid decomposition and selective consumption by herbivores. Larger species were relatively better preserved, especially in the sediments of the more productive lakes where long annual periods of anoxia, or the presence of an algal mat, may inhibit bacterial decomposition. The stratigraphy of many algal remains from one site, Rostherne Mere, accurately reflected the documented fluctuations in the phytoplankton. This correlation enabled the establishment of an 'algal chronology' which provided independent verification of radionuclide dating. Viable akinetes of blue-green algae were recovered from sediments up to 70 years old. Cores from the same site in the mere showed no significant qualitative differences although there were quantitative areal variations. Estimates of standing crop and the concentration of algal remains in either entrapped seston or the sediments were typically within the same order of magnitude. Evidence is presented to refute the suggestion that the mere has recently become enriched by gull excreta. The diatom stratigraphy of two Cumbrian lakes - Grasmere and Elterwater - corresponded to recorded alterations in the phytoplankton, associated with recent changes in sewage treatment. Sediments rich in algal remains are compared to similar deposits in other countries and the possibility that some fossil fuels originated from algal oozes is discussed.

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No description available.

Traditionally, the fossil record has provided the timescale for evolutionary history. However, some evolutionary lineages are completely unrepresented in the fossil record and it is increasingly clear that the rock record in which the fossil record is entombed does not provide a uniform record of all environments at all times - it is systematically biased, but in a predictable manner. Given the frailties of the fossil record, molecular clocks have become the tool of choice in attempts to tell evolutionary time. Molecular clock methods have long been used as a basis for criticising the fossil record, since clocks have invariably yielded estimates of lineage divergence far in excess of palaeontological estimates, leading to the conclusion that the fossil record is woefully incomplete. However, there has been a sea change in perspective among molecular biologists, who are once again looking to the fossil record to better inform the assumptions on which their molecular analyses are based, with the ultimate aim of developing a reliable means of obtaining an evolutionary timescale. The aims of this project were to explore the impact of Bayesian calibration priors on the estimation of molecular divergence times. Analyses of empirical data demonstrate that molecular divergence times are extremely sensitive to the choice of parameters used to inform the calibration priors, and demonstrate that careful evaluation of available fossil evidence is required to inform constraints on node ages. However, competing approaches to calibration have never been tested, because in reality we never know the true time of divergence. The solution is to use simulated data, where the relationship between genetic divergence and fossil evidence is known. Mechanistic models of speciation, non-random fossil preservation and molecular evolution were combined to generate simulated datasets for testing the molecular clock. The results of this research demonstrate that the fossil record can provide accurate, but imprecise, constraints on divergence times, but that the accuracy of molecular divergence times is critically impacted by the way in which fossil data is modelled in the calibration of the molecular clock.

The primary goal of numerical palaeobiology is to understand the processes that generate and eliminate extinct and extant biodiversity. It is important to examine key clades and adaptive assemblages, whose evolution appears intrinsically related to major events in deep time. Mesozoic marine reptiles represent an excellent candidate for investigation, having ascended to ecological dominance in the aftermath of the Permo-Triassic mass extinction and passed through multiple biotic crises. Observations from the rich Triassic marine reptile fossil record highlight diverse ecologies, providing tentative evidence for an exceptional radiation driven by new trophic opportunities - but quantitative tests for this are scarce. Others have highlighted the potential long-term impacts of extinction, and revealed that ichthyosaur evolution was reset following an extinction interval in the Late Triassic. Although a recent body of research has provided new insights into marine reptile macroevolution, many questions remain unanswered. In this thesis, I present several diverse case studies exploring the impacts of ecological opportunity and biotic perturbations in Mesozoic marine reptile macroevolution. Throughout, focus is placed on examining temporal and group-wide patterns of morphological and functional diversity (disparity) and testing rates of phenotypic evolution. Chapters 2-4 focus on Sauropterygia, the most diverse and ecologically disparate Mesozoic marine reptiles, while chapter 5 incorporates all Mesozoic marine reptiles as an inclusive adaptive assemblage. In brief, results show that the Triassic was a time of unusual diversification and high disparity in marine reptile evolution. Multiple lines of evidence show the Triassic was a time of marked morphological, functional and ecological proliferation. Results herein also reveal that sauropterygians, and marine reptiles as a whole, passed through a macroevolutionary bottleneck during the Late Triassic, similar to that identified for ichthyosaurs previously. Overall, this thesis supports the idea that major extinction events can have disproportionate effects on macroevolution, by catalysing exceptional radiations in their aftermath.

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This study aims to explore the skeletal mineralogy of temperate and Polar bryozoans, investigating variability within and between species in relation to methodological, biological and environmental factors. Oceans are becoming warmer and more acidic and it is becoming increasingly important to increase our knowledge about the responses of marine calcifiers to environmental conditions. Bryozoans are important components of the benthic community globally, however prior to this study relatively little was known about their skeleton composition. This study has contributed over 1700 new mineralogical analyses to the field and provided new skeletal profiles for 115 bryozoan species. The study represents by far the most comprehensive regional profile of bryozoan mineralogy to date with 79% of Scottish species analysed. Targeted experiments have resulted in the documentation of impacts of curational procedures on skeletal mineralogy, resulting in recommendations which are pertinent across taxa in the wider fields of both curation and palaeoclimatography. Evidence is presented of mineral localization in specific skeletal features in bryozoan skeletons which adds to the growing body of data showing MgCO3 localization for mechanical and ecological advantage in marine invertebrates. Prior to this study it was proposed that both “active” biological and “passive” environmental controls influence bryozoan skeletal mineralogy. Through the examination of both Polar and Temperate species, this study has provided evidence of biological control of bryozoan mineralogy, while finding no evidence of passive environmental control. This finding precludes the use of bryozoan mineralogy for palaeoclimatic interpretation, for the species included in this study, and it is recommended that future species are chosen carefully and thoroughly calibrated prior to their use as palaeothermometers. Further investigation into the effects of ecological specification on the temperature/mineralogy response may, however, prove an area for fruitful research, enabling prediction of climate change effects on the bryozoan skeletons of ecologically specialised species and providing insights into future changes in community composition.

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No description available.