Complete body fossils have been described from China , and the Middle Cambrian Burgess Shale of British Columbia . Complete body fossils have been formally described from the Lower Cambrian Maotianshan shales of Yunnan , China ( Eognathacantha ercainella Chen & Huang and Protosagitta spinosa Hu ) and the Middle Cambrian Burgess Shale of British Columbia ( Oesia disjuncta Walcott ) .