Evolution within the charophyte genus Harrisichara, late Paleogene, southern England; environmental and biostratigraphic implications

摘要: The Eocene–Oligocene transitional strata of the Hampshire Basin, Isle Wight, provide a unique opportunity to study evolution and biotic turnover in continental realm relation global change occurring at this time. Gyrogonites charophyte genus Harrisichara vary through late Paleogene their abundance has enabled rigorous morphometric study. Morphometric methodologies (including eigenshape analysis) have been used best quantify within genus. Thirteen horizons from six Wight localities representing time period circa 3.5 million years Results show sharp morphological shift between Headon Hill Formation Bembridge Limestone Formation. constitutes doubling volume gyrogonites. observed is argued be functional response changing climate associated increase seasonality. results potential effect increasing both establishment persistence rates Harrisichara. timing coincides with mammal faunal implies wider inferred However, does not evolutionary across ‘Grande Coupure’ (the earliest Oligocene major mammalian event). also coincident zonal boundary vasiformis-tuberculata Zone tuberculata Superzone approach would represent much more robust definition boundary. Biostratigraphy based on multiple studies assemblages individual taxa will facilitate superior correlation should widely applied biostratigraphy.