Shells of 'Oikozetetes' and isolated halkieriid sclerites from a section of the lower Cambrian Mernmerna Formation in the Flinders Ranges, South Australia, are tentatively considered as being derived from the same scleritome. Details of shell morphology and the possible combination of biomineralized shell and sclerites suggest that 'Oikozetetes', if interpreted correctly, is closely related to 'Halkieria'. A new interpretation of 'Oikozetetes' shell morphology, in addition to the first report of paired muscle scars on the interior surface, sheds new light on the possible functional morphology of halkieriid shells and the means of attaching the shell to the body. The occurrence of 'Oikozetetes' in South Australia extends its biostratigraphic range to the lower Cambrian and biogeographic range to East Gondwana.