Geometric morphometric analysis of different species of Cyprideis deriving from the Early Pleistocene record of Greece.

The genus Cyprideis is one of the most widespread ostracod representative of the Pleistocene brackish palaeoenvironments. Especially Cyprideis torosa is often found in great numbers and even in monospecific taphocoenoses and for this reason its study is very useful for palaeoenvironmental reconstructions.  The identification of different species of Cyprideis is often complicated and needs careful morphology inspection. This becomes even more difficult in the case of endemic species which present significant similarities with each other.  In this work, we have studied and analyzed several  Cyprideis species (C.torosa, C. frydaci, C.dictyoti, C. pannonica, C. elisabeta, C. seminulum, C. heterostigma) deriving from brackish palaeoenvironments of a Lower Pleistocene marl sequence in Sousaki Basin (Northeastern Corinth Graben, Greece). More specifically size measurements and geometric morphometrics (lateral valve outline of both right and left valves as well as females and males) were used in order to attest the similarities and dissimilarities between the different species and draw conclusions about their origin.  According to the valve outline and the multivariate analysis a close relationship between the valve shape of all Cyprideis species can be noticed. C. torosa is commonly grouped with C. pannonica except in the male right valve where the two species show some differences.  The endemic species C. frydaci and C. dictyoti can be identified by the differences in the right valve of the male and female respectively.  The other species could not be substantially differentiated using just the outline analysis which possibly denotes their common genetic origin.  The valve outline has proved to be a very useful character for recognizing the different species especially when the two valves of both females and males are considered. More analyses of representative species of Miocene and Pliocene Cyprideis are needed in order to establish their phylogenetic relationships and draw conclusions about their common ancestor.