This study of lower embryophyte spore walls concentrates on the outermost layer, the perispore. The focus of this investigation has been to elucidate the evolution, function and chemistry of the perispore. Lack of knowledge of these aspects of the perispore has resulted in conflicting views which are considered herein. A review documenting the first occurrence of the perispore and its evolution suggests that the first perispore-like layer probably occurs in Cooksonia pertoni (Silurian) and Uskiella spargens (Devonian). It is also considered that perisporal envelopes surrounding cryptospores might constitute the inception of the perispore, dating back even further to the Ordovician. It is proposed that the perispore is an ancestral feature that was lost in certain plant groups but retained in some Trimerophytopsida and Progymnospermopsida. The perispore is now a feature of most extant lower embryophytes. The first true perispore is identified in the basal Upper Devonian species Rhacophyton ceratangium. This work suggests that the perispore is comparable to the plant cuticle in aspects such as chemistry, ultrastructure, and most importantly, the function. The perispore is believed to act as a defence mechanism against pathogenic attack and UV radiation but also provides mechanical support. Silica is thought to either form a discrete layer on some lower embryophyte spores or to be integral with sporopollenin. Additional spore wall stability seems to be the main function of silica. No correlation between the presence of silica in pteridophyte fronds and spores was established. This investigation also comprises the report and analysis of siliceous cubic crystals occurring on Selaginella myosurus megaspores. Although their chemical and crystal log raphic properties could not be fully elucidated, it is suggested that these cubic crystals are a new mineral, formed by an unknown bio-mineralization process occurring in plants. A number of different analytical chemistry techniques were applied in order to elucidate perispore components and the chemical nature of sporopollenin. This study has demonstrated that with current techniques it is difficult to isolate and analyse the perispore and that previously reported data were misinterpreted. It is hypothesised that common plasticizers were wrongly described as sporopollenin compounds. The application of matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-ToF MS) to sporopollenin research is introduced. On the basis of the results presented herein, a revised definition for the term perispore is offered.

No description available.

No description available.

Coccolithophores are a key phytoplankton group that exhibit remarkable diversity in their biology, ecology, and in the highly distinctive morphological architecture of their calcite exoskeletons (coccospheres). Their extensive fossil record is testament to the crucial role that they play in the biogeochemical cycling of carbon through the production and export of inorganic coccoliths and organic matter. This fossil record provides an excellent archive of their biotic responses to environmental variability over thousands to millions of years that can be used to investigate the possible sensitivity of coccolithophores to potential changes in future climate. In this thesis, I explore how the fossil record of coccospheres can be utilized to investigate coccolithophore growth and physiology, providing a new cellular-level perspective on how we understand their interactions with global climate. This work focuses particularly on coccolithophores during the Paleogene, ~66 to ~23 million years ago, that was characterized by initially warm, high CO2 ‘greenhouse’ conditions that progressively cooled, involving substantial restructuring of marine systems. By imaging and measuring thousands of individual coccospheres, I have extensively documented the fundamentals of coccosphere architecture, including coccosphere size and shape and its relationship to coccolith size, number of coccoliths and their arrangement around each cell. This unprecedented dataset reveals the remarkable level of diversity in the architecture of Paleogene coccospheres for the first time, including multiple extinct species that had not previously been observed in this original form. Understanding what this dataset of coccosphere ‘geometry’ can tell us has necessitated the parallel exploration of modern coccolithophore biomineralisation and physiology. My culturing experiments on multiple modern species reveal that cell size and the number of coccoliths per cell is strongly regulated by cellular physiology, specifically responding to a decoupling between cellular division and calcification ability as populations transition between exponential and non-exponential phases of growth. Drawing direct comparisons between the coccosphere geometry of modern and fossil coccolithophores enables a proxy for growth phase to be developed that allows cellular physiology in the fossil record to be directly investigated. This is a potentially powerful new tool for understanding biotic-abiotic interactions in geological time. Furthermore, taxon-specific cellular geometry information provides us with a unique means to begin to reconstruct community-level cellular size structure and, crucially, its associated biovolume. These first reconstructions of community cell size structure across the transition from the Early Eocene greenhouse to the Early Oligocene icehouse demonstrate a massive shift in community biovolume distribution towards larger cells. This radically different-looking community must, in part, reflect the ability of the environment to support the demands of larger cells. Taken in conjunction with inferred changes in nutrient availability by the Late Eocene, this shift in population size structure was likely accompanied by an increase in community biomass, with potentially important implications for carbon export and size-specific grazing. Overall, my research illustrates that coccosphere geometry is a valuable tool for investigating fossil coccolithophore assemblages as populations of individual cells that are recording daily physiological responses to their immediate environment that ultimately determines the response of species and communities to environmental change.

Fossil plants are commonly found preserved as impression/compression fossils; rarer but more informative are three-dimensional fossils, which can preserve the full or partial anatomy. Traditional palaeobotanical techniques for studying these 3D fossils – through physical sectioning to reveal surfaces for inspection – destroy some part of the fossil during preparation, resulting in data-loss. Tomography combined with ‘virtual palaeontology’ can overcome such limitations. This thesis documents the application of tomography to a number of different plant specimens, in various forms of preservation, with the aid of six case-studies. The first five case-studies demonstrate the use of tomographical methods to elucidate anatomical details of fossil plant organs; with each method improving data acquisition compared to the previous. The first details Physical Optical Tomography (POT) as a technique for extracting morphology from specimens where non-invasive x-rays are not amenable or historical physical dataset used. The second shows the advantages of non-destructive X-ray Micro-Tomography (XMT) in revealing the large scale structures of palaeobotanical material. The third investigates XMT combined with traditional destructive techniques to recover both the maximum morphology and cellular detail. The fourth uses XMT combined with Synchrotron Radiation X-ray Micro-Tomography (SRXMT), resulting in improvements to the visualisation of cellular anatomy. The fifth demonstrates that undescribed macro-sized palaeobotanical material may be fully taxonomically described through non-destructive SRXMT alone. The final case-study investigates the advantages and disadvantages of re-studying a pre-existing tomographic dataset and demonstrates that modern software and hardware enable enhanced data extraction. Discussion of the strengths and weaknesses of each method is undertaken, with details presented for the numerous experimental non-destructive XMT and SRXMT scans performed, informing which technique to use for a given fossil. Furthermore, differences in visualisation technique and problems associated with 3D modelling are discussed.

No description available.

No description available.

During the green house world of the Paleocene, Antarctica was covered in extensive forests, even though the continent was situated over the South Pole. Fossil wood is abundant in the marine sequences of Seymour Island, Antarctica. Originating from forests that once grew on a volcanic arc now represented by the Antarctic Peninsula. This research presents a detailed study of the forests and climates of Antarctica primarily using a new assemblage of fossil wood and palynomorphs, directly tied to a sedimentary sequence (K/Pg boundary to Late Paleocene in age) on Seymour Island, which has allowed for a more rigorous interpretation of the composition and structure of the Antarctic Peninsula forests and the climates under which they grew. Tree types identified from fossil wood include: Agathoxylon, Phyllocladoxylon, Protophyllocladoxylon, Podocarpoxylon/Cupressinoxylon, Nothofagoxylon, Weinmannioxylon, Myrceugenelloxylon and Antarctoxylon. Their nearest living relatives (NLR) are found growing in warm to cool temperate Southern Hemisphere forests. Palynomorphs revealed diverse Podocarpaceae including Lagarostrobos franklinii (Phyllocladidites mawsonii) and shrubby angiosperm taxa such as Proteaceae, as well as ferns and mosses. Collective analysis of taxomomy, wood preservation, sedimentology and NLRs indicate that the lowland forests were similar to the cool temperate mixed Nothofagus forests of New Zealand and Thamnic/Implicate forests in Tasmania. Upland floras may have resembled Araucaria – Nothofagus woodlands found in cool temperate Chile today. Coexistence Analysis indicates marginally warm to cool temperate climates with sufficient rainfall for tree growth. Analysis of angiosperm anatomy suggests sufficient water availability. Mean growth ring analysis suggests a trend towards cooler climates from the Early to the Late Paleocene. However, the majority of trees suggest growth under a fluctuating climate. For the first time specific gravity (SG) has been calculated for fossil wood from Antarctica and has provided further insight into the ecology and growth conditions of the trees. Narrow values of SG (0.50 – 0.80) are indicative of a temperate climate in the Paleocene of Antarctica.

No description available.

The Rivington Anglezarke uplands, at the western limits of the Rossendale outlier, are an important landscape resource in industrial Lancashire. Scattered ancient monuments and farmstead ruins stimulate enquiry and suggest long-term human influence while expansive species poor vegetation over peat suggests little has changed over long periods of time. This study seeks insight into such observations by investigation of the vegetational history locked in the peat deposits. Pollen analytical and stratigraphic investigations at 10 sites enable a pattern of vegetational development to be proposed for the last 6000 years. Local pollen assemblage zones, described for each site, are supported by numerical methods in the formulation of a regional pollen assemblage zone scheme for the study area. Chronological support is derived from 20 radiocarbon dates obtained on peat samples from 7 of the sites. A further site, providing evidence of vegetational change from 9000 - 5000 years bp, is dated by palynological cross-reference to the Flandrian type site at Red Koss, Horwich (Hibbert ~, 1971). Evidence is presented for the presence of deciduous woodland throughout the Flandrian II period with increasing modification in the first mil1enium of the Flandrian III culminating in widespread expansion of wet heath from about 3200 years bp which persists across summit plateau for some 2700 years. Evidence is presented for recurrent phases of agricultural activity during this period, one well-marked example being of Romano British provenance. Incising cloughs probably remained well wooded during this period and the clearance of flanking woodlands is associated with increasing anthropogenic influence and a final upsurge in agrarian exploitation persisting from Tudor times to the late 19th Century. The present day vegetation is surveyed. Magnetic measurements and heavy metal ( lead ) assays from three sites are discussed in the context of known extractive activity in the study area during recent centuries. Archaeological and historical evidence is reviewed and linked to the pollen analytical evidence in suggesting possible causes of the vegetational changes.