Darriwilian-Sandbian (Ordovician) Ostracods Of Songliang,Qiaojia,Yunnan Province,SW China

Ostracods range from the Tremadocian(Early Ordovician)to the present,and are one of the most diverse clades of crustaceans.Ordovician is a crucial period for the understanding of their early evolution;however,our knowledge of ostracods of this interval in South China remains limited.In this study,well-preserved ostracods are systematically documented for the first time from the Huadan Formation(Darriwilian-Sandbian,Ordovician)at Songliang of Qiaojia,SW China.Twenty-nine species and 18 genera are identified with new taxon including Vendona spinifera sp.nov.,V.solida sp.nov.,Uhakiella longulata sp.nov.,U.granulireticululata sp.nov.and Nikitinella songliangensis sp.nov.,and three associations are hence recognized,which are Vendona spinifera-Uhakiella longulata,Nikitinella-Medianella-Vendona and Vendona solida-Uhakiella longulata associations.This enables a faunal comparison with those from elsewhere around the world.Also,biostratigraphic implications of the Songliang fauna is discussed,and,based on the presently available data,the macroevolution of Middle-Late Ordovician ostracods in South China is summarized.