The rise of the mesophytic flora

Abstract

The Mesophytic Era began in the Permian when advanced gymnosperms migrated from the uplands, where they had evolved during the latter half of the Pennsylvanian, down into the depositional basins. The Mesophytic Flora orginated at least in part near the paleoequator. The Pennsylvanian tropical uplands where much of this flora evolved were probably cooler, less rainy, and had greater seasonal variations in rainfall than most tropical uplands do now. The Mesophytic Flora appears to have originated in the Pennsylvanian because for the first time stocks of plants (conifers and advanced seed ferns) were available that could really flourish in upland environments. Evolution of the Mesophytic Flora may also have been promoted in the Pennsylvanian by forced migrations of the upland vegetation, by the sparseness of the plants, by climatic changes, and by the high CO₂:O₂ ratio in the atmosphere.