The Neogene Mediterranean origin of Cyprideis torosa (Jones, 1850)

Abstract. Although Cyprideis torosa is one of the most studied ostracods, its ecophenotypic variability has always impeded a clear definition of its carapace morphology. As a consequence, it is often difficult to identify this species in fossil material and very little is known about its phylogenetic origin. In this paper, we attempt to answer two main questions: when and from what species did C. torosa originate? To reach this goal we first analysed living and Recent populations of C. torosa collected from different salinity environments to define its variability. We found that the valve outline, the size of rounded normal sieve pores and the percentage width of the anterior inner lamella seem to vary independently of salinity. Secondly, to look for possible ancestors we analysed several Neogene species and found that Cyprideis sp. from the mid-Serravallian of Spain could possibly be the common ancestor of the Late Miocene Mediterranean and Lake Pannon lineages and that C. torosa is strictly linked to the Mediterranean stock, particularly to the phyletic lineage C. ruggierii–C. crotonensis. In this framework Cyprideis gr. torosa originated in the late Tortonian and C. torosa s.s. is thought to have been differentiated from C. crotonensis at the beginning of the Calabrian.

Supplementary material: biometric tables and the list of the examined material is available at https://dx.doi.org/10.6084/m9.figshare.c.3636170.v1