The age of the Yukiang(Yujiang) Formation has been shrouded in controversy for more than75 years.New investigation at the Liujing section,Hengxian County,Guangxi,has revealed a conodont sequence assignable to two Early Devonian conodont zonations:the Eognathodus kindlei?-Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest.The Gaoling and Mahuangling members of the Nahkaoling(Nagaoling) Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei?-Polygnathus pireneae Zone.The co-occurrence of Polygnathus pireneae and Pol.sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone.However,precise level identification of the Pragian-Emsian Boundary(PEB) in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member.The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.
Anomalocaridids were large predators of the Cambrian seas at the top of the trophic pyramid.Complete anomalocaridid specimens have been rarely discovered and the rigid isolated frontal appendages and mouthparts are more commonly preserved.Here we study new material of the frontal appendages from the Wulongqing Formation,Cambrian Stage 4,Series 2 near Kunming,eastern Yunnan.Two new forms of anomalocaridid frontal appendages are described,namely Anomalocaris kunmingensis sp.nov.and Paranomalocaris multisegmentalis gen.nov.,sp.nov.The frontal appendage of A.kunmingensis sp.nov.probably comprises15 podomeres of which the first one has a weakened skeletoned,the second one is armed with small spines,and the third one is armed with remarkably robust proximal ventral spines with 6 anisomerous auxiliary spines;paired auxiliary spines are associated with podomeres 4–14;podomeres 12–14 are armed with paired dorsal spines,and the last podomere bears 2 distal spines,one spine distinctly larger than the other.The frontal appendage of P.multisegmentalis tapered backwards,consisting of 22 visible podomeres;the most ventral spine is armed with 5 pairs of auxiliary spines,and podomeres 12–21 bear dorsal spines,the last podomere with 2 small distal spines.The new material provides additional evidence for our understanding of the diversity of anomalocaridids in the Cambrian.The morphology of these new finds may indicate the importance of different feeding strategies of anomalocaridids in the Cambrian ecosystem.
