ABSTRACT: The taxonomy of Paratethyan Middle Miocene calcareous nannofossils is reviewed and revised. Two new species, Syracosphaera croatica and Syracosphaera horvati, are proposed. Comparative study of coeval Neogene nannofossils from NHM and ODP (Ocean Drilling Project) reference collections give differences and similarities between the investigated areas (first occurrence, theirmorphology and dimensions). Other studies data on taxonomy are reviewed including palaeoecological and biostratigraphic applications.