Reappraisal of the Eocene whiptail stingrays (Myliobatiformes, Dasyatidae) of the Bolca Lagerstätte, Italy.

The Eocene whiptail stingrays of the family Dasyatidae from the Bolca Lagerstätte, NE Italy, are revised herein in detail. The analysis of the anatomical and morphometric features allows us to identify the species "Dasyatis" zigni (Molin, 1861) as a junior synonym of "D." muricatus (Volta, 1796), and to assign it to the new genus Tethytrygon gen. n. This new taxon exhibits a unique combination of features (e.g., rhombic disc wider than long, elongated tail folds fail to reach the tip of the tail, thorns absent, single serrated tail sting, "caniniform" teeth on upper jaw, tooth crown ornamentation absent, 175-179 vertebrae, 108-117 pectoral radials, 24-27 pelvic radials and other features of clasper anatomy) that clearly support its attribution to the subfamily Neotrygoninae of the stingray family Dasyatidae. The morphological and phylogenetic affinities of Tethytrygon gen. n. with the living neotrygonines (Neotrygon and Taeniura) suggest a close association of this taxon with the tropical shallow-water habitats hypothesized for the Bolca palaeoenvironment during the early Eocene. Moreover, the analysis of the fossil occurrences of the neotrygonines provides new insights into the role of the Tethys for the origin and evolutionary history of certain whiptail stingrays.