Quantitative Study Of Global Brachiopod Palaeobiogeography From Changhsingian(Late Permian) To Rhaetian(Late Triassic)

The Changhsing(Late-Permian)and Triassic epochs persisted about 53 million years recorded a series of critical evolutionary and geological event such as global plate tectonic activity,Pangaea changed from gathered into cracked phase,global sea-level fluctuation,and biodiversity plunged at the end-Permian and end-Triassic.This series of events has greatly influenced the development and evolution from the Paleozoic to modern evolved fauna.The biogeographical distribution range variety and the formation and evolution of biogeographical provinces were not only the directly result of the evolution events such as Bio migration,diffusion or segregation,but also the reflection of the related geological events.The study of the biogeographical distribution and biogeographical provincial series change from Late-Permian to Triassic has great significance which is significant methods to understand the coordinate evolution between the biological macroevolution and geological event in history.In this paper,the Filemaker database was take as the data acquisition and management platform,on which the taxonomy and palaeogeographic distribution database of the global brachiopods from Changhsing(Late-Permian)to Rhaetian(Late-Triassic)was collected,entered and constructed.After the data cleaning and integration,9934 effective records of the brachiopod from Changhsing(Late-Permian)to Rhaetian(Late-Triassic)were obtained,which is from 1421 fossil location belong to 181 palaeogeographic analysis unit(belonging to 2458 species,481 genera,105 families,11 orders).After data conversion,abundance data matrix and binary data matrix of global brachiopod genera occurrence from nine periods have been obtain.On this based,brachiopod biogeographically provinces from Changhsing(Late-Permian)to Rhaetian(Late-Triassic)has been comprehensive analysis,distinguish and divide by cluster analysis(CA),non metric multidimensional scaling(NMDS)and the minimum spanning tree(MST)three multivariate analysis methods under different faunal similarity coefficient.Analysis found that the biogeographically distribution pattern of global brachiopod has been an important turn and change during the Late-Permian Changhsing period to Late-Triassic Rhaetian stage.The global brachiopod fauna of Late-Permian Changhsing period could be divided into two clarity biogeogrphic region as Tethyan and Gondwana region.In the Tethyan region,the boundaries between Cathaysian,Himalayan and Western Thethyan Province were also distinct.Affected by the mass extinction during the end Paleozoic near the P/T boundary,global brachiopod was devastated,the original ecosysterm and Biological community were destroyed,as while as the biogeographic region vanished.Some endemic biogeographic unit did not appear until the end Early-Triassic Olenekian.The biogeographic region of global brachiopod was not reconstructed until the Middle-Triassic Anisian as Tethyan and Gondwana region.The former was divided into Cathaysian Western and Tethyan Province.Although the Siberia and Himalaya area were belong to the Tethyan,the link was not closely.In the Ladinian,the link between Siberia area and Tethyan region was weakening and finally formed the independent Boreal region.The range of the Boreal region expanded toward the South direction and once reached the mid latitude zone of Southern Hemisphere at Late-Triassic Norian.During the Rhaetian stage,the range of Tethyan and Gondwana region were contraction,and the Boreal region returned into the mid high latitude zone of Northern Hemisphere.It found,moreover,the biogeographic provincial series change and trend of the global brachiopod from Late-Permian Changhsing to Late-Triassic Rhaetian were related to the major global geohistorical events and biological events in this period.Especially,the “Gondwana-Tethyan” distichous pattern of Changhsing period changed into the “Gondwana-Tethyan-Boreal” trichotomous pattern of the Late-Triassic.This process was closely related to the process which the Laurussia and Siberia moving toward and integrate.With the continued closed of Laurussia and Siberia from the Early-Triassic Olenekian stage,the Urals Ocean between the two continents was narrowing and finally shut at the end Mid-Triassic.The channel which communicated the brachiopod in the Paleo-Tethys ocean and Palaeo-Pacific was vanished.The geographic isolation made by the global plate tectonics directly infected and controlled the brachiopod biogeographical provincial series change process during this period.The Channel closure caused by the plate tectonics further brings to the significant change of the large scale global ocean circulation model.In addition,the global sea-level changes,global climate warming,transgression and other geohistorical events also had influence on the migration and diffusion of brachiopod in the certain degree,then further affected the geographic distribution and the biogeographical provincial series evolution.The long-term dynamic evolution process and trend of geographic distribution and the biogeographical provincial series,as while as the reflection and response process of the contemporary global major geohistirical events and biological events,provided the important method and approach for understanding and resuming of the plate tectonic and palaeoplate location.It verified that the plate tectonic and variety of plate location in biological way,also provided an important support and evident for resuming and reconstructing the palaeoplate,and the palaeogeographic distribution map.