Five new bivalved arthropods are described from the Lower Cambrian Chengjiang fauna, Yunnan, China. All of them are rare in the fauna, represented by one or two individuals among thousands of specimens. Four of the five new taxa are preserved with soft parts that show a clear distinction between them. The new taxa provide new important information concerning the soft bodied and limb characters of the early bivalved arthropods. A significant lesson is that, not knowing any soft parts, it is virtually impossible to place systematically a new type of bivalved carapace. It is often impossible even to tell if it is a crustacean or not. A second antenna in the shape of a "great appendage" is identified for the first time among the bivalved arthropods. The new taxa include representatives of the order Pectocaridida, the families Pectocarididae. Clypecarididae and Occacarididae, the genera and species Pectocaris spatiosa, Clypecaris pteroidea, Occacaris oviformis, Forfexicaris valida and Yunnanocaris megista.