Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 7 uppsatser.

La transition Crétacé inférieur-Crétacé supérieur (environ 100 millions d'années) marque une période cruciale pour l'évolution de certaines plantes à graines. Elle correspond à la rapide radiation des plantes à fleurs et à la réorganisation écologique des Angiospermes et des conifères. Cependant, notre connaissance des plantes à graines durant le Crétacé moyen et en Laurasie reste encore très partielle. Pendant la dernière décennie, la microtomographie synchrotron s'est avérée une technique d'imagerie très performante pour l'étude les structures internes de divers fossiles. Jusqu'à maintenant, les applications de cette technique n'ont été que très limitées en paléobotanique. C'est dans ce contexte que cette thèse s'est intéressée : (1) au développement de nouvelles approches d'imagerie par tomographie, utiles en paléobotanique, et sur différents types de préservation ; (2) à l'utilisation de ces nouvelles approches pour compléter notre connaissance de la morpho-anatomie, la systématique, la diversité, et l'écologie des plantes à graines laurasiatiques du Crétacé moyen. Ainsi, un peu plus d'une centaine de spécimens (e.g. inflorescences, fleurs, fruits, et grains de pollen d'Angiospermes ; cônes and axes feuillés de conifères) provenant de gisements paléontologiques français ont été étudiés par tomographie synchrotron. Pour la première fois, de nombreuses fleurs très diversifiées sont décrites dans les dépôts cénomaniens de Charente-Maritime et du Gard (Ouest et Sud-Est de la France). Dans certains cas, toutes les unités florales du périanthe, de l'androcée, et du gynécée sont préservées. Un nouveau protocole combinant microtomographie par contraste de phase de propagation et nano-holotomographie a été développé pour étudier des petits spécimens isolés tels que des fleurs préservées sous forme de fusain ou de lignite (taille de voxel proche de 50 nm). Les données tomographiques permettent de les décrire de la morphologie générale à la paroi des grains de pollen, in situ, dans les étamines. Ces fleurs sont majoritairement attribuées à des Lauraceae et des Platanaceae. De plus, des nodules siliceux, opaques, denses, et contenant des inclusions végétales sont ici signalés dans les dépôts cénomaniens de Charente-Maritime. Ils contiennent d'abondants restes de conifères. Ils sont préservés sous forme de perminéralisation siliceuse et en trois dimensions. Ce travail propose un protocole tomographique multi-échelles, haute résolution et haute énergie, utile à l'étude d'inclusions végétales contenues à l'intérieur de nodules rocheux de grande dimension. Le conifère Glenrosa est décrit pour la première fois, de la morphologie générale des structures végétatives et reproductives à l'histologie. Ce travail soutient que pendant le Cénomanien, les environnements les plus ouverts sur la mer étaient dominés par les conifères alors que les milieux littoraux plus internes et protégés montraient quant à eux des flores à dominante angiospermienne. / The Lower Cretaceous-Upper Cretaceous transition (about 100 million years ago) stands as a crucial period for the evolution of some seed plants. It consists of the brutal radiation of flowering plants and an ecological reorganisation of Angiosperms and conifers. However, our knowledge of mid-Cretaceous Laurasian seed plants remains partial. During the last decade, synchrotron microtomography has successfully been employed for non-destructively imaging inner structures of various types of fossil remains. To date, the applications of this technique in palaeobotany are still limited. This thesis focuses on: (1) developing new tomographic imaging approaches at the European Synchrotron Radiation Facility (ESRF, Grenoble, France), relevant to palaeobotany, and especially for investigating various kinds of plant preservations; (2) applying these approaches to improve our knowledge about the morpho-anatomy, the systematics, the diversity, and the ecology of Laurasian seed plants during the mid-Cretaceous. Hundreds of unique or rare mid-Cretaceous fossil plant specimens (e.g. inflorescences, flowers, fruits, and pollen grains of Angiosperms; cones and leafy axes of conifers) from French Cretaceous deposits were imaged and investigated using several new synchrotron tomographic protocols. For the first time, abundant and diverse fossil flowers are described from the Cenomanian deposits of Charente-Maritime and Gard (western and southeastern France, respectively). In some cases, all floral units of the perianth, the androecium, and the gynoecium are preserved. A new tomographic approach combining propagation phase contrast X-ray microtomography and nano-holotomography was developed to image those small and isolated plant specimens such as charcoalified/lignitized fossil flowers (up to 50 nm of voxel size). This allows the description of fossil flowers, from their gross morphology to the micromorphology of the exine of in situ pollen grains inside stamens. They are mainly and unambiguously ascribed to Lauraceae and Platanaceae. In addition, large, opaque and dense silica-rich flint nodules containing plant inclusions are reported from the Cenomanian deposits of Charente-Maritime. They contain abundant hidden conifer. These Cenomanian conifers are exceptionally well-preserved in three dimensions and consist of siliceous permineralisation. We propose a multiscale, high resolution and high energy tomographic protocol useful for the study of plant inclusions contained inside large rocky nodules. We study the partially unexplored extinct conifer Glenrosa, from the gross morphology to the histology of its vegetative and reproductive structures. This work supports that during the Cenomanian and in coastal areas, on the one hand, palaeoenvironments which were highly influenced by marine inputs were probably dominated by conifers. On the other hand, innermost and protected palaeoenvironments showed Angiosperm-dominated floras.

The osteology of the Upper Triassic podokesaurid Syntarsus rhodesiensis is described, based on a series of 30+ individuals representing all skeletal elements, recovered since the description of the holotype (Raath, 1969). A brief account of the geology of the finds is given, with an attempt at a reconstruction of the palaaoenvironment. The excellence of preservation of the bones has permitted an attempt at the restoration of soft tissues including the brain, cranial nerves, main cranial blood vessels and the musculature of the jaws, neck and limbs. Histological sections of limb bones have shown that the compact bone was highly vascular, and this, together with the structure of the brain, palaeoenvironmental considerations, social behaviour and group structure, leads to the conclusion that Syntarsus was an endothermic homeotherm inhabiting a hot arid region at the end of the Triassic, with a social organisation into "flocks" in which females predominated numerically. Clear evidence of sexual dimorphism is presented. Syntarsus is reconstructed as a bipedal, saltatorial predator which differs in subtle, but probably generically significant, characteristics from the closely related North American genus, Coelophysis. Its anatomy characterises it as a medium-sized agile animal with a highly kinetic skull; incipiently opposable pollex in the raptorial manus; highly cursorial hindlimb; and with features in the dentition and hallux which suggest a grooming function. It is concluded that the Triassic coelurosaurian stock provided an advanced and well adapted base from which the successful coelurosaur radiation into the later Mesozoic sprang, and that this stock was physiologically pre-adapted for the emergence of the avian (and possibly the pterosaur) lineages in the Jurassic

O naturalista dinamarquês Peter Wilhelm Lund (1801-1880), considerado o pai da Paleontologia brasileira, professava a chamada Teoria do Catastrofismo, do Barão Georges Cuvier. Foi para tentar comprovar esta teoria que o naturalista escavou milhares de fósseis nas cavernas de Lagoa Santa (MG) entre 1835 e 1844, quando descreveu dezenas de espécies extintas do período Pleistoceno. Durante este trabalho, Lund descobriu os esqueletos fossilizados de cerca de 30 seres humanos, que ficaram conhecidos como os Homens de Lagoa Santa. Logo após esta descoberta, o naturalista enviou suas coleções para a Dinamarca e pôs fim nos trabalhos de campo, sem no entanto voltar ao seu país e permanecendo no Brasil até sua morte. A maior questão não respondida sobre a vida de Peter Lund, e o objetivo deste trabalho, é entender porque afinal ele parou de pesquisar? O próprio Lund alegou falta de dinheiro. Mas seus biógrafos escolheram como bode expiatório o cansaço físico e intelectual após anos de trabalho ininterrupto nas cavernas. A resposta, no entanto, encontra-se na coleção de cartas de Lund, arquivadas na Biblioteca Real de Copenhagen. O presente trabalho é resultado do estudo de uma pequena parte desta correspondência. Analisou-se a vida do naturalista à luz da sua relação com a família, mestres e amigos no Brasil e na Dinamarca, na esperança de identificar a razão para o término das pesquisas de um dos mais influentes cientistas do Brasil no século XIX. / The Danish naturalist Peter Wilhelm Lund (1801-1880), also called \"Brazilian Paleontology\'s father\", was a proponent of the Catastrophism theory formulated by Georges Cuvier. In search of a proof for this theory, Lund excavated thousands of fossils from the caves of Lagoa Santa (MG) between 1835 and 1844, eventually describing dozens of extinct Pleistocene species. Meanwhile, Lund found fossilized skeletons of some 30 human individuals, that became known as the People of Lagoa Santa. Soon after that, Lund sent his collections to Denmark and put an end to his fieldwork. But he never returned to his country, remaining in Brazil until his death. A major question that remains about Lund\'s life, and the object of this work, is to know why after all he stopped his research? Lund\'s himself wrote that lack of money was the cause of it. But his biographers choose as scapegoat his physical condition and intellectual tiredness after years of uninterrupted work in the caves. The answer, however, is to be found in Lund\'s letter collection, archived at the Copenhagen Royal Library. The present work is the result of the study of a small part of this correspondence. By analyzing the naturalist\'s life and his relations to his family, masters and colleagues both in Brazil and Denmark, my hope was to identify the reason for the end the research of one of the most influent scientists of Brazil in the Nineteenth century.

O naturalista dinamarquês Peter Wilhelm Lund (1801-1880), considerado o pai da Paleontologia brasileira, professava a chamada Teoria do Catastrofismo, do Barão Georges Cuvier. Foi para tentar comprovar esta teoria que o naturalista escavou milhares de fósseis nas cavernas de Lagoa Santa (MG) entre 1835 e 1844, quando descreveu dezenas de espécies extintas do período Pleistoceno. Durante este trabalho, Lund descobriu os esqueletos fossilizados de cerca de 30 seres humanos, que ficaram conhecidos como os Homens de Lagoa Santa. Logo após esta descoberta, o naturalista enviou suas coleções para a Dinamarca e pôs fim nos trabalhos de campo, sem no entanto voltar ao seu país e permanecendo no Brasil até sua morte. A maior questão não respondida sobre a vida de Peter Lund, e o objetivo deste trabalho, é entender porque afinal ele parou de pesquisar? O próprio Lund alegou falta de dinheiro. Mas seus biógrafos escolheram como bode expiatório o cansaço físico e intelectual após anos de trabalho ininterrupto nas cavernas. A resposta, no entanto, encontra-se na coleção de cartas de Lund, arquivadas na Biblioteca Real de Copenhagen. O presente trabalho é resultado do estudo de uma pequena parte desta correspondência. Analisou-se a vida do naturalista à luz da sua relação com a família, mestres e amigos no Brasil e na Dinamarca, na esperança de identificar a razão para o término das pesquisas de um dos mais influentes cientistas do Brasil no século XIX. / The Danish naturalist Peter Wilhelm Lund (1801-1880), also called \"Brazilian Paleontology\'s father\", was a proponent of the Catastrophism theory formulated by Georges Cuvier. In search of a proof for this theory, Lund excavated thousands of fossils from the caves of Lagoa Santa (MG) between 1835 and 1844, eventually describing dozens of extinct Pleistocene species. Meanwhile, Lund found fossilized skeletons of some 30 human individuals, that became known as the People of Lagoa Santa. Soon after that, Lund sent his collections to Denmark and put an end to his fieldwork. But he never returned to his country, remaining in Brazil until his death. A major question that remains about Lund\'s life, and the object of this work, is to know why after all he stopped his research? Lund\'s himself wrote that lack of money was the cause of it. But his biographers choose as scapegoat his physical condition and intellectual tiredness after years of uninterrupted work in the caves. The answer, however, is to be found in Lund\'s letter collection, archived at the Copenhagen Royal Library. The present work is the result of the study of a small part of this correspondence. By analyzing the naturalist\'s life and his relations to his family, masters and colleagues both in Brazil and Denmark, my hope was to identify the reason for the end the research of one of the most influent scientists of Brazil in the Nineteenth century.

At present the Karoo Basin covers approximately 20 000 km2. It is a large intracratonic basin which, from Carboniferous to Jurassic times, was infilled with a succession of sediments ranging from glacial deposits to those deposited in warm, equable conditions. The Beaufort Group forms part of this succession, and was deposited in a terrestrial, river dominated environment. The dominant lithologies exposed in the Estcourt region in the KwaZulu-Natal Midlands belong to the lower and middle Beaufort divided by the PermoTriassic boundary. The Permo-Triassic palaeoenvironment in this region is reconstructed using sedimentary profiles combined with the study of the fossil remains discovered in the area, including plant, body, and trace fossils. The lower Beaufort sediments in this region belong to the Estcourt Formation, and the Middle Beaufort sediments to the Belmont Formation. The Estcourt Formation is dominated by a succession of alternating sandstones, siltstones and mudstones, which are interpreted as representing sediments deposited in a fluvial-floodplain environment, which can be divided into two sub-environments. The first is dominated by sediments that were deposited by meandering rivers on a semi-arid floodplain, and the second sub-environment is represented by those sediments deposited in lacustrine environments. Both of these subenvironments are closely linked and alternate in the rock record indicating many episodes of transgressive-regressive lacustrine episodes. The Estcourt Formation can be closely correlated with the lower Beaufort sediments mapped in other regions of the Karoo Basin, indicating similar climatic and environmental controls throughout the Karoo Basin of southern Africa. The Estcourt Formation also contains a wide variety of body and trace fossils. The PermoTriassic boundary can be traced along the western border of Estcourt by using the distribution pattern of the two mammal-like reptiles Dicynodon and Lystrosaurus. There is evidence of an overlap in the distribution between these to mammal-like reptiles, which together with palaeoflora evidence, indicates that Lystrosaurus evolved during the Late Permian and not Early Triassic as previously thought. The first Triassic sediments are represented in the Estcourt region by a series of maroon shales which can be correlated with the Palingkloof Member. / Thesis (M.Sc.)-University of Natal, 1997.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

The Late Rhaetian (Late Triassic) extinction event is characterised by shelled species showing a reduction in size, and thickness, which together with changed mineralogy is thought to be as a result of increased atmospheric pCO2 levels. Similar morphological changes have been demonstrated for extant species exposed experimentally to high CO2 leading to the hypothesis that Late Triassic extinctions were linked with global ocean acidification and increased oceanic palaeotemperatures. Consequently, the aim of this present work was to test this ocean acidification hypothesis by investigating morphological changes in selected shelled fossil species across this extinction event, and attempt to correlate them with changes in environmental temperature and pCO2. The abundance, size, shell thickness and mineralogy was determined for three common species, the bivalves Liostrea hisingeri and Plagiostoma gigantea and the ostracod Ogmoconchella aspinata collected from Triassic and Jurassic rocks from two locations in southwest England. Palaeotemperature was reconstructed from examination of these fossils and from the literature and atmospheric pCO2 estimated from published accounts. The shell size of bivalves increased during periods of high pCO2 and high palaeotemperature at both locations. Ostracod carapace sizes increased at St Audrie’s Bay but decreased at Lyme Regis during periods of high pCO2, while ostracod carapace size decreased during periods of high palaeotemperature at St Audrie’s Bay. However, ostracod shell thickness increased and decreased as pCO2 increased but shows no relationship with palaeotemperature at either location. Laboratory experiments on the effect of elevated pCO2 and elevated temperature on three modern species of ostracod was carried out. Modern species Leptocythere sp. and L. castanea subjected to either elevated pCO2 or elevated temperature showed increased dissolution, however size and thickness did not significantly change. In the same experimental conditions L. lacertosa showed increased dissolution however size continued to increase, while thickness was maintained. Comparison of fossil bivalve and ostracod data to modern high pCO2 and high temperature experiments illustrates some correlations to the modern experiments results indicating high pCO2 and high palaeotemperature conditions could have been occurring during the Triassic-Jurassic boundary interval. From the evidence presented, combined with an appropriate trigger (CAMP volcanism), it can be concluded that both ocean acidification and palaeotemperature were contributing to the species adaptations identified across the Triassic-Jurassic boundary interval.

No description available.

This study aims to unravel the ecological and evolutionary dynamics within the calcareous nannofossil communities at the Eocene/Oligocene (E/O) transition and during the Oligocene time when Cenozoic 'icehouse' conditions were established. The main question this study aims to answer is whether the changes in the nannofossil assemblages were controlled by intrinsic evolutionary trends or if the changes were controlled by environmental factors such as changes in temperature and nutrient availability in the surface water. These questions are addressed with detailed analyses of the taxonomy, biostratigraphy and fluctuations in abundance and diversity of calcareous nannofossil assemblages from a continuous latest Eocene through Oligocene sediment section from the ODP Site 1218 (8°53.38´N, 135°22.00´W), paleo-equatorial Pacific Ocean. An improved nannofossil taxonomy and biostratigraphy has been established. At the E/O transition, changes in the nannofossil preservation mimics changes in calcium carbonate content. A detailed investigation of late Eocene and Oligocene sediments yields age estimates for ten nannofossil bioevents. Morphometric studies of the Reticulofenestra umbilicus-R. hillae show that these cannot be subdivided into two different morphospecies. Based on different morphometry and stratigraphic ranges, the Oligocene Sphenolithus lineage appears to be the result of a combined anagenetic and cladogenetic evolution. A new nannolith species is described: Triquetrorhabdulus longus. High-resolution nannofossil data indicate changes in the composition, abundance and diversity of the mid-Oligocene assemblages. Intervals of high diversity index coincide with Oi-glaciation events. However, visual examination of the variations in abundance of nannofossil taxa do not appear to correlate with changes in either oxygen or carbon isotopes. This presumably indicates that a dynamic equilibrium did not exist between these Oligocene nannoplankton assemblages and changes in surface water temperature or productivity conditions. / Doctoral Thesis in Marine Geoscience at Stockholm University, Sweden 2009