A new genus and species of deep-sea hatchetfish, Discosternon federicae gen. et sp. nov., is described from the Middle Miocene (Serravallian) calciturbititic deposits of the Tufillo Unit exposed near the town of Gessopalena, central Italy. It is based on a single, very small, well-preserved and nearly complete specimen that exhibits a discoid physiognomy and a unique combination of features, many of which are reductive (loss of dorsal blade, loss of anal-fin hiatus, loss of abdominal keel-like structure, reduction of number of supraneurals, reduction of number of caudal vertebrae, presence of slender neural and haemal spines, external surface of cleithrum smooth). The comparative morphological analysis indicates that Discosternon is probably related to the derived genera Horbatshia and Sternoptyx. The highly reduced body size and the possession of many reductive characters indicate that Discosternon can be presumed to be a miniature fish. Anatomical and morphofunctional considerations suggest that Discosternon possibly was a midwater plankton feeder characterized by a reduced locomotory ability.
