A Trilobite-like Arthropod From The Cambrian Xiaoshiba Lagerstatte

The Hongjingshao Formation from Kumming-Wuding area was once regarded as a reddish sequence without any fossils.Recently the finding of Xiaoshiba Lagerstatte from Kumming-Wuding area in Yunnan Province(west region of the Xiaojiang Fault)indicates that there are abundant fossils with exceptional preservation in this area,and the Hongjingshao Formation is therefore not a reddish formation without any fossils as previously regarded.In comparison of their occurrences,the Xiaoshiba Lagerstatte is approximately equal to the Malong fauna,later than the Chengjiang biota,but earlier than the Guanshang biota.Actually they constitute three successive evolutionary fossil assemblages.In this study fourteen invertebrate taxa,most of which with extraordinary preservation,were reported from the Xiaoshiba Lagerstatte-a typical Cambrian Burgess-Shale-type deposit,including Chengjiangocaris kunmingensis,Fuxianhuia xiaoshibaensis,Wiwaxia foliosa,Collinsium ciliosum,Selkirkia sinica and Hongshiyanaspis yiliangensis and so on,Zhiwenia coronata gen.et sp.nov.is also exquisitely preserved.The discovery provides fresh insights into the understanding of the Cambrian explosion.To date Zhiwenia coronata gen.et sp.nov.as a typical trilobike-like arthropod,has only been found from the early Cambrian(Stage 3)Xiaoshiba Lagerstatte in the eastern Yunnan Province.Z coronata gen.et sp.nov.consists of a broad cephalon,multi-segmented thorax and a leaf-like telson tapering backwards.The head is underneath a subelliptical cephalic shield,bearing a pair of anterolateral notches locating 1/3-2/3 of the cephalic shield and accommodating eyes.A pair of antennae extends anterolaterally from 1/3 of the cephalic shield,consisting of 17 to 20 annuli.The thorax is composed of 20 tergites,of which the first is crescentic in outline in dorsal view;others are almost identical in a sub-trapezoidal shape.Appendages are biramous,showing no sign of coxa;each endopod bears 5 podomeres,including a terminal claw.The leaf-like telson is a terminal piece with 5 pairs of lateral spine.Z coronata is characterized by having a pair of notches in the single cephalic shield,where the stalked eyes are inserted.In previous studies such notches were merely known from Sidneyia inexpectans and Luohuilinella rarus.