An overview of Neogene brackish leptocytherids from Italy and Spain: Biochronological and palaeogeographical implications

An overview of the Neogene euryhaline leptocytherids from Italian and Spanish basins is reported, together with their chronological and geographical distributions. Eight genera (or subgenera) have been considered: Mediocytherideis s.s., M. (Sylvestra), Chartocythere, Leptocythere, Tavanicythere, Amnicythere, Euxinocythere s.s. and E. (Maeotocythere). The study has shown that these leptocytherids could be a valuable biochronological tool in both marginal marine and the athalassic saline environments, since, even at generic level, they show separate temporal distributions. For example, the presence of Chartocythere and Euxinocythere s.s. in the Mediterranean seems to be limited to the Late Serravallian; Tavanicythere seems to have been exclusively distributed during the Late Miocene, with different species spanning the Late Tortonian and Early Messinian; M. (Sylvestra) seems to attain its maximum diversity in the same time-interval; the widespreading of Amnicythere and E. (Maeotocythere) in the Mediterranean marks the Latest Messinian lago-mare event (about 5.5-5.3 Ma); the important radiation of Leptocythere characterises the Pliocene. Moreover, a comparative analysis between Neogene Mediterranean and Paratethyan leptocytherids has shown that the geographical and stratigraphical distribution of the eight genera analysed matches the palaeogeographic events that affected the Peri-Tethyan realm during Neogene.