Freshwater ostracod assemblages from San Demetrio Synthem (L'Aquila Basin, central Apennines, Italy), dating back to the late Piacenzian-Gelasian, are studied. Six genera and eight species are recognised, six of which are new: Caspiocypris amiterni Spadi & Gliozzi sp. nov., C. bosii Spadi & Gliozzi sp. nov., C. nicandroi Spadi & Gliozzi sp. nov., C. vestinae Spadi & Gliozzi sp. nov., Cypria bikeratia Spadi & Gliozzi sp. nov., and Ilyocypris ilae Spadi & Gliozzi sp. nov. Additionally, one fragmentary valve referred to Paralimnocythere cf. P. dictyonalis Medici, Ceci & Gliozzi, 2011, one valve ascribed to Amnicythere ex gr. stanchevae Krstic, 1975, one fragment tentatively identified as Limnocythere? sp. and four poorly preserved valves of Cypridoidea indet. were also recovered. The genus Caspiocypris is revised, and an emended diagnosis is provided. Comparisons are made with the most similar co-generic species occurring in the Neogene of Italy and the Paratethyan domain. The ostracod fauna of the San Demetrio Synthem shows the greatest affinity at the generic level with the Pontian (Messinian-Zanclean) ostracods of the Pannonic, Dacic and Euxinic Basins. To explain this affinity, two hypotheses are discussed: (1) passive dispersal of Paratethyan forms into the Italian Plio-Pleistocene palaeolakes; and (2) endemic evolution of several species in different Plio-Pleistocene palaeolakes from the Paratethyan-like late Messinian Lago-Mare ostracod fauna of the Palaeomediterranean area.
