All three clades containing Prunum and “Volvarina” species contain morphological features that do not collectively appear in any other living or fossil marginellid species (see above).
2001, Ross H. Nehm, “6: Linking Evolutionary Pattern and Development Process in Marginellid Gastropods”, in Alan H. Cheetham, Jeremy B. C. Jackson, Scott Lidgard, Frank K. McKinney, editors, Evolutionary Patterns: Growth, Form, and Tempo in the Fossil Record, page 166