Distribution of some species of fresh and brackish-water Ostracoda from the lower Pleistocene of SE Sicily

Biogeographia vol. XXX - 2011 (Pubblicato il 23 dicembre 2011) La Biogeografia della Sicilia Distribution of some species of fresh and brackish—water Ostracoda from the lower Pleistocene of SE Sicily FRANCESCO SCIUTO Dzpartimento di Scienze Biologic/ae, Geologic/Je eAmbz'entcz[z', Corso Itzzlzkz 55, 95129 Catania (Italy); e—mai/.-ficiuto @um'ct. it Key words: Ostracods, fresh and brackish water, Sicily, palaeobiogeography, biogeography. SUMMARY Lower Pleistocene marine sediments, evolving upwards to continental deposits, widely crop out along the south- western edge of the Hyblean Plateau in the Comiso-Vittoria area. This environmental transition is well recorded, along the right side of the Ippari river near “Cartiera Mulino” (Vittoria, Ragusa). Eight samples were collected in a geological section from this locality. The basal and middle layers contain abundant shallow—water marine ostracods whereas microfaunas from the top of the section only consist ofostracods which exclusively thrive in freshwater en- vironments. Three among the brackish and freshwater species are recorded (Aurilzz zzrborescem, Ilyocjypris gibba and Candomz neglecta) with remarks on their geographical and stratigraphical distribution. INTRODUCTION Ostracods are the most common extant arthropod group with abundant and continuous fossil record, due to their usually mineralised, easily preservable ex- oskeletons. They are able to thrive in all aquatic environments, mostly in marine settings from the sea level to oceanic depths, but also in continental waters: lakes, rivers and even humid ephemeral ponds. Consequently, ostracods represent an useful tool for palaeoenvironmental reconstructions and palaeobiogeographical analyses (Ducasse and Peypouquet, 1979; Babinot and Lethiers, 1984; Guernet and Lethiers, 1984; Carbonel, 1987; Passlovv, 1997; Martens et al., 2008). The present analysis is a contribution to the knowledge of the palaeobio— geographic distribution of/lurila czrborescem (Brady, 1865), Ilyocypris gibbzz (Ramdohr, 1808) and Ccmdomz neglecta Sars 1887, here first recorded from Lower Pleistocene sediments from SE Sicily.