Micropalaeontology of the Leintwardine Group (Ludlow Series, Silurian) in the Welsh Borderland, Wales and Estonia.

An integrated biostratigraphical scheme consisting of 6 biozones, based on the distribution of microfossil groups (acritarch, algal, conodont and ostracod), is proposed for the Leintwardine Group of the type area and coeval sections in the Welsh Basin. 20 species of prasinophycean algae (2 new species and 12 in open nomenclature), 114 acritarch species (2 new genera, 8 new species, 52 in open nomenclature and 1 new combination), 12 ostracod species (6 in open nomenclature), 10 conodont species (3 in open nomenclature), 6 spore species (5 in open nomenclature) and 8 chitinozoan species (4 in open nomenclature) are described from the Welsh Basin. New genera are: Maceriasphaera and Flammulasphaera. New named species are: Cymatiosphaera intricata, Cymatiosphaera pumila, Cymbosphaeridium molyneuxii, Eisenackidium parvum, Flammulasphaera bella, Lophosphaeridium hillii, Maceriasphaera pustula, Percultisphaera iticompta, Salopidium aldridgei and Umbellasphaeridium richardsii. Graphic correlation reveals that an hiatus at Sunnyhill Quarry corresponds to the major lithological change at the base of the Leintvvardine Group at Aymestrey. A stratigraphic break has also been recognised within the Leintwardine Group on the Whitcliffe. Palaeoenvironmental and palaeoecological investigation of acritarchs and algae show, that different morphological groups occupied separate habitats. Palynomorphs were also recovered from the Sauvere, Himmiste and Uduvere beds (Paadla Stage, Ludlow Series) and the Tahula Beds (Pridoli Series) of Saaremaa Island, Estonia. 14 species of prasinophycean algae (2 new and 6 in open nomenclature), 79 acritarch species (4 new, 40 in open nomenclature and 2 new combinations), 6 spore species (5 in open nomenclature) and 12 chitinozoan species (6 in open nomenclature and 3 new described in open nomenclature) have been recognised. New named species are: Cymatiosphaera caperata, Dictyotidium contortwn, Helosphaeridium siveterii, Lophosphaeridium peatii, Salopidium balticum and Vermiculatisphaera hispida. Acritarchs suggest that the Tahula Beds correlate with the Ludfordian Stage in Great Britain and are older than previously described.