Microstructure Of Coniopteris From Jurassic In Sandaoling,Xinjiang And Its Geological Significance

Coniopteris is a dominant genus in the Middle Jurassic flora all over the world.This flora is rich in Ginkgo and fern,especially Coniopteris usually identified as the Coniopteris-Phoenicopsis flora.The Jurassic strata in North Xinjiang are well developed and rich in fossils of the Coniopteris,which can provide detailed materials for paleontology and stratigraphic research.As the Jurassic period is an important coal accumulation and oil production period in China,the study of this paper has very important practical significance.In addition,tracheids of rachis in fern are rarely found in the study of Palaeobotany.Therefore,the study of tracheids has important theoretical significance in the evolution of plant systems and the analysis of ecological environment.This paper selects the fossils of the Jurassic genus Coniopteris from Hami,Xinjiang,and describes eight species of Coniopteris,of which 2 species in situ spore and two species analyses was performed.Cluster analysis was performed based on 15 features of 52 species of Dicksoniaceae using PAST software.A new species,Coniopteris sandaolingensis X.C.Yuan et B.N.Sun sp.nov.was reported.Based on these characteristics,data,and comparisons with other studies,the evolution,decline,and extinction of the genus Coniopteris were discussed,and the paleoclimate and its stratigraphic significance were analyzed.Present fossil's characteristics are highly consistent,all show long-flat cells,vertical walls,and no trichome.The tracheid molecules found in the rachis of three species also showed more primitive features.Cluster analysis shows that there are certain links between the genus of the Dicksoniaceae.The research results show: The tracheid structure of the Coniopteris shows that its water transfer capacity is very poor,combined with the living Dicksoniaceae grows on the water's edge.We speculate that it was warm and humid in the middle Jurassic Sandaoling area,and there were lake or multiple rivers.The decay and even death of the Coniopteris is related to its original tracheid structure and its evolutionary delay.Combining with the current numbers of Coniopteris fossils,the features of first pinnule on the basiscopic side is aphlebiform.Compared with the domestic and foreign plants,we consider these strata belongs to the Aalenian-Bajocian period of the early Middle Jurassic.The results of cluster analysis show that Coniopteris is the basic genus of Dicksoniaceae and it may be evolved to other genus after a certain development.