The characterization of the Permian Cathaysia Flora based on fossil cuticles

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The Permian witnessed one of the most extreme climate transitions of the Phanerozoic, from deep icehouse conditions in the Early Permian to a greenhouse state by the Late Permian time. The collision of Gondwana with Eurasia in the Late Pennsylvanian resulted in the formation of thesupercontinent Pangea, which had a significant impact on the climate. Cathaysia is one of the four floral provinces that emerged during the late Paleozoic. The Cathaysia flora comprises several elements that are also known from Euramerica, but also a number of endemic taxa. As thetaxonomy is primarily based on macromorphological criteria and relationships of taxa often remain unclear, detailed studies of the Cathaysia flora are necessary for a better understanding of its relationships to the other floral provinces. Cuticular analysis not only allows a much more precisedefinition and delimitation of individual taxa, but it also provides important information on the palaeoecology and palaeoclimate on the basis of biological criteria, i.e. the epidermal anatomy. This project will focus on the Palougou section in NW-Shanxi, which is now generally regarded as a standard reference section for the Cathaysia flora. This continuously exposed section includes several horizons with plants with good cuticle preservation and starts in the Upper Carboniferous and runs up to the Permian-Triassic boundary. This project embraces a comprehensive study of cuticles from the successive cuticle-bearing horizons in order to: (1) establish a sound definition, delimitation, and ecological characterization of individual taxa on the basis of biological criteria, (2) reconstruct palaeoatmospheric CO2 levels of the successive associations based on stomatal densities (SD) and indices (SI), and (3) compare Cathaysia floras with Euramerican floras from thesimilar palaeolatitudes. We anticipate that this project will lead to a much better understanding of the Cathaysia flora and its relations to other time-equivalent palaeo(sub)tropical floras.