Nupela fennica and N. elegantula lack capitate apices. Nupela impexiformis and N. wellneri have lanceolate or elliptic-lanceolate valves, with distinctly convex, rather than parallel, margins. Valves of N. giluwensis are narrowly elliptic, and not linear-lanceolate. Valves of N. schoemaniana have a very small central area and subcapitate apices.