A minute pelecypod, T. paparua n. gen. and n. sp. is described from a limestone lens of late Middle Cambrian age occurring within the Tasman Formation northwest Nelson Province, South Island, New Zealand. The morphology of Tuarangia is distinct from that of fordilloids and a new order, the Tuarangiida, together with an accompanying subordinal taxon is erected. Several steinkerns of Tuarangia bear impressions of a microscopic shell fabric interpreted as foliated structure. Tuarangia is tentatively assigned to the Subclass Pteriomorpha, the only subclass of pelecypods known presently to secrete a calcite foliated shell fabric.