Mummpikia gen. nov and the origin of calcitic-shelled brachiopods

Phosphatised limestone-hosted and shale-hosted specimens of the obolellid Mummpikia nuda gen. et comb. nov. and two further unidentified obolellids from the Early Cambrian Mural Formation (jasper National Park, Canadian Rocky Mountains) provide novel insights into the shell microstructure of obolellids and the nature of their pedicle. The shell was penetrated by abundant canals of a sub-pm diameter and the anterior tip of the delthyrium forms a projection into the body cavity that is penetrated by a thin canal. It is argued that both shell microstructure and posterior margin are linguliformean characters and that obolellids hold a position basal in the rhynchonelliform stem-group.