Study On Cambrian System Kaili Formation Brachiopoda In Southeast Of Guizhou Province

The Cambrian Kaili biota(Stage 5)from eastern Guizhou,South China encompasses more than 140 genera from 11 metazoan body plans across all kingdom-rank lineages,which,togethers with the Chengjiang biota(Stage 3)from Yunnan,China and the Burges shale(Stage 5)from Canada,becoming the most important Burgess Shale-type Lagerst?ten in understanding the Cambrian Explosion.Brachiopods are especially abundant and diverse in the Kaili biota(next only to the dominant arthropods),so that they are an important component of the benthic communities in the Cambrian period.Morphological,palaeoecological and taphonomical analyses of numberous brachiopods from the Kaili biota,are the subjects of the present Ph.D.thesis.Firstly,all the brachiopod fossils collected from the Kaili Formation(which yields the biota)at four sections in three areas are systematically described,i.e.,the Wuliu-Zengjiaya and Miaobanpo sections near the Balang village,Jianhe County,the Sanwan section in Nangao Town,Danzhai County,and the Fujiachong section in Zhuping Town,Zhenyuan County.The brachiopods comprise 2 subdivisions,3 classes,4 order,6 families and 11 genus,13 species in total,including 2 species indeterminate and 6 species nova(2 species have been published),i.e.Linguliformea Williams et al.,1996,belonging to 8 genus and 9 species: Lingulella bynguanoensis Roberts & Jell,1990,Lingulepis taijiangensis Huang,Wang,Zhao & Dai,1994,Palaeobolus bretonensis Matthew,1899,Acrothele bohemica Barrande,1990,Acrothele kailiensis sp.nov,Linnarssonia tumida Henderson & MacKinnon,1981,Paterina jianhensis sp.nov,Dictyonina balangia sp.nov,Micromitra sp.,and Rhynchonelliformea Williams et al.,1996,belonging to 3 genus 4 species: Kutorgina dengzhouensis sp.nov.,Nisusia guizhouensis Mao,Zhao,Wang & Topper,2017,Nisusia granosa Mao,Wang & Zhao,2014 and Eoconcha sp.Within the Kaili biota,over 430 specimens belong to two species of Nisusia,N.guizhouensis(Mao et al.,2017)and N.granosa(Mao et al.,2014),are described,The second is Acrothele,the number of which has reached more than 170 belonging to 2 species.There is a species nova,i.e.Acrothele bohemica and Acrothele kailiensis sp.nov.,Palaeobolus ranks the third in the number,with the number of specimen of more than 110,belonging only to 1 species.Genus with specimen amount decreasing successively are Linnarsson,Paterina,Eoconcha,Dictyonina,Lingulepis,Micromitra,and Lingulella.These 8 genus have low disparity belonging only to one species.Most genus belong to Inarticulata,and part of them belong to Articulata.This reflects that in the early period of the third Cambrian,Articulata has increased evidently,Linguliformea has taken up a significant position in Cambrian period.In addition,statistics of the stratigraphical ranges of the brachiopods from the Kaili Formation at the Wuliu-Zengjiaya and the Miaobanpo sections showing that the Kaili Formation can be divided into three brachiopod assemblage biozones,in ascending order,the Nisusia guizhouensis – Palaeobolus bretonensis Ass.Zone,Paterina jianhensis – Kutorgina dengzhouensis Ass.Zone and Acrothele bohemica – Acrothele kailiensis Ass.Zone.The biozone frame of the brachiopods from the Kaili Formation coincide with the three thilobite zones of the formation,which helps to define the base of Cambrian Series 3and Stage 5 in the Kaili Formation based on the first appearance datum(FAD)of the trilobite Oryctocephalus indicus.Studies on biostratigraphy,palaeobiogeography,and evolution of the Kaili brachiopods have been done along with comparing to composition characteristics of brachiopods from other iconic Burges shale-type biotas around the world.Specifically,only one out of nine genera(Kutorgina)from the Chengjiang biota occuring in the Kaili biota.However,four out of six genera of brachiopods(Lingulella,Paterina,Micromitra and Nisusia)from the Burgess Shale,seems similar to those of the Kaili biota.A juvenile planktophile of these brachiopods might give rise to such a similarity.In addition,the Kaili biota is approximately equivalent to the Burgess Shale in age(Cambrian Series 3 and Stage 5),and South China and Laurentia were at a same latitude may also the possible causes.At last,morphological function,life style and burial characteristics of brachiopods from the Kaili biota have also been analysed based on modern ecological theories.A small number of fossils exhibit interesting ecological information and burial characteristics.For instance,some individual showing coexistent relations of mutualistic symbiosis,mutualistic burial,and fixed base with Echinodermata,Medusiform,Cnidaria and Large Bivalved Arthropods.Dozens of Acrothele with two shells preserved,indicating that they underwent little decay or mechanical damage before entering the diagenetic environment.These specimens,therefore,are suggested to have been buried in life by deposition events or transported from nearby environments.