Cythereis donzei nov sp (Trachybeleridinae, Ostracoda) of the lowermost Cretaceous (upper Berriasian) from southeastern France.

Cythereis donzei is a new ostracode species of the Upper Berriasian shallow-marine coastal deposits of the Jura Mountains and Provence (southeastern France). It is the oldest and most primitive species of the genus Cythereis and can be considered as the ancestor of Cythereis matura OERTLI from the Lower Valanginian (Arzier Marls) in the Swiss and French Jura Mountains and Cythereis prisca DONZE fron the Berriasian/Valanginian boundary in the Vocontian deeper marine facies boarding the Jura and Provence platforms. This new species is a basic marker for the understanding of the Trachyleberidinae origin and evolution in the Tethyan Area, an ostracode group at the basis of several phylogenetic lineages of biostratigraphical significance.