The characterization of the Permian Cathaysia Flora based on fossil cuticles

二叠纪见证了显生宙最极端的气候变化之一，从二叠纪早期的深冰窖条件到二叠纪晚期的温室状态。冈瓦纳与欧亚大陆在宾夕法尼亚晚期的碰撞导致了超级大陆盘古大陆的形成，这对气候产生了重大影响。华夏是古生代晚期出现的四个花省之一。华夏植物区系包括几个已知的来自欧洲的元素，但也有一些特有的分类群。由于华夏属植物的分类主要基于宏观形态标准，而且分类群之间的关系往往不明确，因此对华夏属植物区系的详细研究对于更好地了解其与其他植物省的关系是必要的。角质层分析不仅可以更精确地定义和划分单个分类群，而且还可以根据生物标准（即表皮解剖）提供有关古生态和古气候的重要信息。本项目将重点研究晋西北地区的八楼沟剖面，该剖面目前被普遍认为是华夏植物区系的标准参考剖面。这个连续暴露的剖面包括几个层位，植物的角质层保存良好，从上石炭世开始，一直延伸到二叠纪-三叠纪边界。本项目对连续层位的角质层进行了全面的研究，以期：(1)在生物学标准的基础上建立完整的个体分类群的定义、划分和生态特征；(2)基于气孔密度（SD）和指数（SI）重建连续群落的古大气CO2水平；(3)比较来自相似古纬度的华北植物区系与欧美植物区系。我们期望这个项目将有助于更好地了解华夏植物区系及其与其他时间相当的古（亚）热带植物区系的关系。

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.