Palaeogeographic and palaeoclimatic considerations based on Ordovician to Lochkovian vegetation
Philippe Steemans, Charles H. Wellman, Philippe Gerrienne, 2010. "Palaeogeographic and palaeoclimatic considerations based on Ordovician to Lochkovian vegetation", The Terrestrialization Process: Modelling Complex Interactions at the Biosphere–Geosphere Interface, M. Vecoli, G. Clément, B. Meyer-Berthaud
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This paper summarizes research on Ordovician to Lochkovian vegetation development in a palaeogeographic framework. A terrestrialization model is described. Palaeogeographic maps are modified to explain the vegetation migrations. Land plants first evolved on the Gondwana plate and colonized Avalonia and later Laurentia and Baltica when those plates were in close proximity (Ashgill–Llandovery). South America was colonized during the Llandovery following the collapse of the ice sheet centred on the southern pole which had previously been an impassable barrier for miospores. An Aeronian–Telychian event related to the global early Silurian transgression modified the vegetation by destroying biotopes where the earliest vegetation was thriving. During the regression, trilete spore-producing plants appear to have been more able to respond to environmental changes and dominated the vegetation from the Homerian. Cryptospore-producing plants could survive under a wide range of climates, which helped them to survive during the Hirnantian glaciation. On the contrary, the earliest trilete spore-producing plants were probably climatically restricted, as suggested by latitudinal variation in assemblage composition. By the end of the Silurian, there were several phytogeographic units. Information on the earliest vegetation favours palaeogeographic reconstructions where plates are in close proximity.
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The Terrestrialization Process: Modelling Complex Interactions at the Biosphere–Geosphere Interface
The invasion of the land by plants (‘terrestrialization’) was one of the most significant evolutionary events in the history of life on Earth, and correlates in time with periods of major palaeoenvironmental perturbations. The development of a vegetation cover on the previously barren land surfaces impacted on the global biogeochemical cycles and the geological processes of erosion and sediment transport. The terrestrialization of plants preceded the rise of major new groups of animals, such as insects and tetrapods, the latter numbering some 24 000 living species, including ourselves. Early land-plant evolution also correlates with the most spectacular decline of atmospheric CO2 concentration of Phanerozoic times and with the onset of a protracted period of glacial conditions on Earth. This book includes a selection of papers covering different aspects of the terrestrialization, from palaeobotany to vertebrate palaeontology and geochemistry, promoting a multidisciplinary approach to the understanding of the co-evolution of life and its environments during Early to Mid-Palaeozoic times.