ABSTRACT: The Global Stratotype Section and Point for the base of the Middle Eocene Lutetian Stage has recently been defined at the calcareous nannofossil CP12a/b zonal boundary at the Gorrondatxe section (Biscay, Basque Country). In terms of planktonic foraminifera, the lowest occurrence of a species defined at this section, namely Morozovella gorrondatxensis, appears as one of the events that may best serve to approximate the Ypresian/Lutetian boundary, as it is only 1.2 myr younger than the calcareous nannofossil CP12a/b zonal boundary. However, Morozovella gorrondatxensis was recently re-categorized as being merely a junior synonym of Morozovella crater. In this paper we argue that M. gorrondatxensis is in fact a separate species, that its paleobiogeographic distribution was supra-regional, and that it therefore has a great potential for early Lutetian biostratigraphic refinements.