On the identity of Rissoa radiata balkei Verduin, 1976: redefining a NE Atlantic rissoid species

In 1976, Verduin described the subspecies Pusillina radiata balkei from Galicia, NW Spain. Despite a detailed description, differentiation from the Mediterranean Pusillina radiata (R. A. Philippi, 1836) remained unclear. As a result the new taxon remained poorly understood and has since then been rarely recorded. Based on new findings in NW Spain the taxon is further defined, the variability in its shell described, and its present-day distribution established. As result the taxon is elevated to species rank whose name is Pusillina balkei (Verduin, 1976), has a NE Atlantic distribution and is distinct from the Mediterranean Pusillina radiata. The new insights into the variability of the species helps us to identify Late Pleistocene populations from the North Sea Basin.