Study On Leptosporangiate Fern Family Botryopteridaceae And Paleoecology Environment From The Early Permian Of North China

Plant fossils of coal balls are abundant in North China.This thesis studies several selected specimens of coal ball plants from Shanxi and Shandong Province,North China.The described botryopterid fern from the Permian Cathaysian Flora is of great interest and presents a unique opportunity to understand the plant anatomical structure and systematic palaeobotany.It can also reconstruct the individual plants and restore ecological appearance of flora from the perspective of paleoecology.The present thesis has important reference value for the paleoecology,palaeogeography,palaeoenvironment of fern.Anatomically preserved botryopterid specimens from Cisuralian-aged(early Permian)coal balls in No.7 coal seam of the Xishan coal field in Taiyuan of Shanxi Province and No.16 coal seam of the Taozao coal field in the south of Shandong Province,North China are investigated.The fossil materials include stems,attached and detached petioles,adventitious roots,epiphyllous shoots,sporangia and spores belonging to the same kind of plant.By the observation of the continuous peels and slides,a new early leptosporangiate fern genus and two new species are identified and described.Differences with previously known genera of Botryopteridaceae lead to creation of new genus,Diodonopteris gracilis that demonstrates features that overlap to some extent with those of previously known genera within Botryopteridaceae.Rachides of Diodonopteris gracilis are D-shaped in cross section and the xylem is curved adaxially with one protoxylem ridge at each lateral margin.Some fossil materials show great similarities to the genus Rhabdoxylon but are not consistent with its any known species,so it is necessary to create a new species Rhabdoxylon taiyuanense to include the stem and petioles.This thesis also studies Diodonopteris cf.gracilis,Diodonopteris sp.,Rhabdoxylon sp.,Botryopteris cf.forensis and Botryopteris tridentata.From the perspective of palaeoecology,some conclusions are as follows: 1)The ecological habits of Botryopteridaceae.Based on the specimens,semi-upright or upright growth habits are considered of coal ball plants in the Early Permian in North China.2)The paleogeography and paleoenvironment of the North China is tropical and humid.3)The ecology analyzation shows that the Diodonopteris gracilis in Shanxi coal ball were buried in situ.But Diodonopteris cf.gracilis in Shandong coal ball might have been transported from different areas.4)Coal plants community are analyzed by the statistics of plant community.The study focuses on coal ball plants community succession process from Xishan coal field in Taiyuan.However,early leptosporangiate ferns are very rare,and are in China only known from fragmentary specimens.The Botryopteridaceae from Euramerica and Gondwana are mostly Carboniferous in age and only a few are of Permian age.The present thesis represents the first account of botryopterid plant fossils with stems,petioles,rachides,sporangia and spore preserved from the Permian of China,offering new insight into the diversity,structure and habit of these plants in the Cathaysian Flora.The discovery of a new type of the Palaeozoic leptosporangiate fern in China has led to reevaluating the systematic relationships among species of the Botryopteridaceae.This thesis gives a review to understand the floral composition and taxonomic diversity within various ecological and stratigraphic contexts.