Jurassic Clam Shrimp From Xinjiang-Qinghai

Jurassic deposits in China are mainly of continental origin and contain an abundance of fossil clam shrimp.Fossil clam shrimp evolved rapidly,and they are widespread and always found at many horizons with a large number of individuals.This makes them useful tools for biostratigraphic subdivision and correlation of non-marine successions.There are a number of large stable inland basins which deposits thick Jurassic in western China,and the Jurassic in these areas is continuous and well-exposed.These basins are always important for the study of clam shrimp.In the last decades,although abundant Jurassic clam shrimp of various genera have been reported from western China,only a small volume of published studies provided detailed taxonomic information.In addition,most of the studies were based on optical microscopy,it means that some fine structures of potential taxonomic value could be overlooked.As a result,the biostratigraphic correlation based on a rough classification is often inaccurate.In the present dissertation,based on the newly collected fossil material from several crucial Jurassic sections and the scanning electron microscopy,20 Jurassic clam shrimp species in twelve genera are described,including a new genus and six new species.The new genus is Punctatolimnadia gen.nov.and six new species are Bulbilimnadia xinjiangensis sp.nov.,Nothocarapacestheria punctatus sp.nov.,Punctatolimnadia punctulosus gen.et sp.nov.,P.rotunda gen.et sp.nov.,Linglongtaestheria turpanensis sp.nov.and Punctatestheria foveolatus sp.nov.Besides,diagnoses are revised for the genera Iliestheria,Nothocarapacestheria,Qaidamestheria,Tianshanograpta and species Euestheria jingyuanensis.Additionally,the species Triglypta manasica Wang,1985 has been removed from Triglypta and revised as Linglongtaestheria?manasica(Wang,1985).Accordingly,in Xinjiang area,the Early Jurassic clam shrimp fauna includes nine species in five genera,namely,Bulbilimnadia xinjiangensis sp.nov.,Iliestheria nilkaensis,I.urumqiensis,I.xinjiangensis,Nothocarapacestheria punctatus sp.nov.,N.cf.soturnensis,Punctatestheria karamayensis,Punctatolimnadia punctulosus gen.et sp.nov.,P.rotunda gen.et sp.nov.Nothocarapacestheria was found from both the Badaowan and Sangonghe Formations.Iliestheria was found from the bottom of the Sangonghe Formation.The Sangonghe Formation is dominant by Punctatolimnadia.Eleven species in eight genera are described from the Middle-Upper Jurassic of Xinjiang.They are Aquilonoglypta cf.yabulaiensis,Euestheria cf.jingyuanensis,Sinokontikia lianmuqinensis,Tianshanograpta elongata,T turfanensis,Linglongtaestheria?manasica(Wang),L.turpanensis sp.nov.,Turfanograpta elongata,T.?cf.huoyanshanensis,Punctatestheria foveolatus sp.nov.and P.lianmuqinensis.Punctatestheria foveolatus sp.nov.is the only species discovered from the Sanjianfang Formation.Both Tianshanograpta and Sinokontikia lianmuqinensis are only found from the top of the Qiketai Formation,and Tianshanograpta is the dominant element.Turfanograpta and Punctatestheria are found from the middle to the top of the Qiketai Formation.Notably,no Triglypta has been found from the Sanjianfang,Qiketai and Toutunhe Formations.All of the Triglypta-like individuals,which resemble Triglypta in size,shape and ornamentation,also have fine reticulation ornamented on their larval valve,and they are different from the true Triglypta whose dorsal side of the carapace only ornamented by puncta.