A Plio–Pleistocene Caspiocypris species flock (Candoninae, Ostracoda) from the Palaeolake Tiberino (Umbria, central Italy)

The Tiberino Basin is a wide Plio-Pleistocene intermountain basin located in central Apennine (central Italy). Its sedimentary infill is made of a thick succession of Pliocene-early Quaternary continental deposits, the oldest of which can be referred to the Fosso Bianco Formation, composed of grey clays deposited in a huge (at least 500 km(2)) and relatively deep (not less than 50 m) lake, the Palaeolake Tiberino. We analyse the lacustrine ostracod assemblages from the Fosso Bianco Formation and provide descriptions of five new species included in the subfamily Candoninae (Caspiocypris basilicii sp. nov., Caspiocypris perusia sp. nov., Caspiocypris posteroacuta sp. nov., Caspiocypris tiberina sp. nov. and Caspiocypris tuderis sp. nov.)) and one new species included in the subfamily Limnocytherinae (Paralimnocythere umbra sp. nov.)). The five species of Caspiocypris seem to represent a species flock, i.e. Caspiocypris includes a group of closely related species characterized by monophyly, endemism and speciosity, confirming the 'ancient lake' nature of the Palaeolake Tiberino during the Piacenzian-Gelasian. The ostracod assemblage points to a relatively deep-water and low energy lacustrine environment marked by a high level of endemism.