Middle Jurassic Flora From Daohugou, Ningcheng, Inner Mongolia,

Daohugou area is located adjacent to the borders of Liaoning Province, HebeiProvince and Inner Mongolia Autonomous Region. Recently, abundant fossils havebeen discovered in this locality, indicating that there was a Middle Jurassic terrestrialecosystem with a high level of biodiversity in Daohugou area. However, only a smallnumber of fossil plants have been reported. In this thesis, detailed taxonomic studies ofplant megafossils and sporopollen fossils from the Daohugou area are presented. Basedon the analysis of flora composition, we can reconstruct the palaeoclimate,palaeoecology and palaeogeography in Middle Jurassic Daohugou area. Meanwhile,we first focus on the damage type by insects on fossil plants and the plants’ defencemechanism, providing significant evidence for studying the plant-insect interaction andco-evolution in geological time.All the fossils were collected from the lower part of the Middle JurassicJiulongshan Formation. Jiulongshan Formation consists of lacustrine deposits, mostlycontaining tuffaceous siltstone, sandstone and mudstone. Cuticle of the fossil plants iswell-preserved.51species of33genera were identified, including Bryopsida sensu lato,Lycopsida, Sphenopsida, Filicopsida, Cycadopsida, Ginkgopsida, Czekanowskiales,Coniferopsida, fructus et semina, spermatophyte insertae sedis and plantae insertaesedis. Gymnosperms and Filicopsida play the most important part in Middle JurassicDaohugou flora. Among the gymnosperms, Cycadopsida has the largest number ofspecies but lower genus diversity. According to the flora composition and distributionof the known species, the age of Daohugou flora should be Middle Jurassic. Forty-four genera and87species were identified to comprise the Middle Jurassicpalynoflora in Daohugou area. Among them, pollen of gymnosperms dominates,followed by spores of pteridophytes. The former mainly consists of bisaccate pollen ofconifers and monosulcate pollen of Cycadales, Bennettitales or Ginkgoales.Classopollis also plays an important role. The latter are mainly composed of Cyathidites,Deltoidospora, Granulatisporites, Leiotriletes and Osmundacidites. All of thesebasically reflect the features of Middle Jurassic palynoflora. Compared to some MiddleJurassic palynofloras in North China, it is convinced that the age of Daohugou fossil-bearing strata should be late Middle Jurassic. The occurrence of tuffaceous componentsindirectly proves that there were frequent volcanic activities during this period.In the Middle Jurassic, Daohugou area is rich in ferns, ginkgoaleans, cycadaleansand conifers, mainly indicating the climate of warm-temperate to medium-temperateregions. Based on the plant assemblage, Daohugou flora is similar to that in the MiddleJurassic Northern Floristic Province of China. It is probable that, due to the seasonaland precipitation variations, it may experience the change between humid, warmclimate and dry, hot climate. By studying the ecological and climatic preferences of themain plant groups, four types of communities in Jurassic Daohugou are proposed. Theyare shoreside-wetland (Bryopsida, Lycopsida and Sphenopsida), lowland (Filicopsidaand Cycadopsida), sloping-land (Ginkgopsida and Czekanowskiales) and upland(Coniferopsida).In Daohugou area, the damage type on fossil plants are divided into margin feeding,surface feeding, hole feeding and oviposition. Plants also adopt some defensivemeasures accordingly, including physical and chemical defence. Statistic analysisshows that damage types mainly consist of margin feeding, while the surface feeding,hole feeding and ovipositon rarely occur. The damage on Bennettitales is much worsethan that on Ginkgoales, which may be caused by the excellent insect resistance ofginkgoaleans. Among the Bennettitales, Anomozamites suffer the most damages, morethan Pterophyllum. The surface trichomes on Anomozamites and stiff leaf blades maybe the evidence of plants’self-protection in the process of co-evolution with insects.