VARIABILITY OF SHELL IN GASTROPODS OF THE GENUS BORYSTHENIA LINDHOLM, 1914: TESTING THE STATISTICAL APPROACH IN SEARCH OF TRAITS FOR THE RECENT AND FOSSIL SPECIES DELIMITATION

Abstract

The gastropod mollusc genus Borysthenia Lindholm, 1914 comprises many species throughout Europe, Asia, North Africa and North America but species delimitation, based mainly on shell morphology (only possible concerning the fossil records) is often disputable. Statistical methods used to test if the shell measurements are reliable traits in delimitation of recent and fossil species in gastropod molluscs of the genus Borysthenia. Our analyses based on quantitative study of over 100 specimens of the Borysthenia species both modern and fossil. It is concluded that the dimensional characteristics of their shell are suitable for the differentiation of both recent and fossil (at least of Pontian age) species through the statistical processing of quantitative data. Through the morphological study of type material, taxonomic status of B. jalpuchense Gozhik, 2002 and B. vinogradovkaense Gozhik, 2002 described from the middle-pontian deposits of Ukraine revised. It is suggested that these taxa are considered two distinct though close relative extinct species. Stratigraphic range of B. jalpuchense is expanded up to the Lower Pontian. All the modern individuals of Borysthenia involved are attributed to B. menkeana (Jelski, 1863) due to their exact correspondence to the lectotype of this species.