Microstructure Of Several Fossil Plants From Permian And Cretaceous In Hexi Area,gansu And Geoglogical Significance

The Permian strata is well-preserved and has abundant plant fossils in Longshou mountain area of Hexi,Gansu Province.A fern fossil,Compsopteris,was collected and studied in details.The Compsopteris in this paper has relatively complete vegetative leaves and cuticle layer,which was identified as Compsopteris wongii based on the macroscopic morphology and microscopic structure.It is the first report and the complete microstrucutre of Compsopteris in Shanxi formation in the Longshou mountain.The Compsopteris used to be considered as the seed fern.In this paper,there is a relatively clear impression of sporangium on the leaf fossil of the Compsopteris wongii.Combined with previous studies,the author believes that some Compsopteris in the class serpentine may be true ferns.The early Cretaceous strata are well preserved and is rich in plant and animal fossils in the Beishan area of Gansu Province.In this paper,the female cone,several male cone fossils and a large number of vegetative branch fossils of Elatides and a large number of vegetative branch fossils of Solenites were collected in the research area.The reproductive organs of the Pinaceae and the vegetative leaves of the Solenites were also reported for the first time in this area.The fossils of female cone,male cone and vegetative branch of the Pinaceae were preserved well.It was identified as Elatides by studying the morphology and microstructural structure of the fossils.Through the detailed identification and comparison of the known fossils species of cone and vegetative branch,it is found that the characteristic combination of fossils and known species is different.Therefore,a new species,Elatides beishanensis sp.nov.,was established.Through the study of the Czekanowskiales,it was identified as the Solenites.Through the study of the macro structure and micro structure of the fossils and the comparison of the known Ginkgo and Czekanowskiales,it was found that the fossil and the known species feature combination is different,so I made a new species: Solenites beishanensis sp.nov..At the same time,we find a kind of known species: Solenites luanpingensis Wang.According to previous studies,the Elatides was first appeared in the upper Triassic of Sweden.They expanded in the Middle and Late Jurassic.They extended to southern Europe,Siberia and northern China,as well as the Iran plate.To the Early Cretaceous,the distribution continued to expand.The climate differences between the north and south of China regions before the late Jurassic epoch should account for the failure of spruce to spread from northern China to southern China during the Jurassic period.In this paper,the leaves of the Solenites were compared with several Czekanowskiales.It is most closely related to Solenites and Czekanowskia,but differs from both of them.It is speculated that this species may be a transitional type between the Solenites and the Czekanowskia.Previous studies suggested that the Pangaea monsoons formed as a result of plate movement occurred in the Late Paleozoic(Late Carboniferous to Cisuralian)and ended in the Early Cretaceous when the Pangaea disassembled.Based on fossils and previous studies,the author briefly analyzed the effects of giant monsoons on the study area and on the spreading of spruce.The cuticle characteristics of fossil plants can be used to infer the living environment of plants.In this paper,the cuticle of several fossil plants in Beishan area is relatively thin,and the stomatal apparatus is slightly depressed.The Early Cretaceous environment of Beishan region was a warm,humid subtropical climate with seasonal variation,which may be influenced by the giant monsoon at the end of the period.