Batfishes from the Eocene of Monte Bolca

Batfishes of the family Ogcocephalidae are derived lophiiform fishes characterized by having a dorsoventrally depressed body and a distinctive series of morphological features. A new genus and species of batfish, Tarkus squirei gen. et sp. nov., is described from the Eocene (Ypresian) limestone of the celebrated locality of Monte Bolca, Italy. It is based on five well-preserved specimens that display a unique combination of characters (body moderately depressed; disk rounded in outline; caudal peduncle thick and stout; frontals with median groove for the illicium; teeth present on jaws and palate; illicial bone pitted and trilobate; body covered with thick slightly overlapping tubercles) that support its recognition as a new genus of the family Ogcocephalidae. Tarkus gen. nov. is also characterized by having distally branched pectoral-fin rays, a condition unique within the family, and by a peculiar structure of the axial skeleton, which possibly represents the plesiomorphic state for the ogcocephalids. Tarkus gen. nov. shows a certain degree of phenetic affinity with the extant shallow-water batfish genera Halieutaea and (more particularly) Halieutichthys. The specimens of this taxon are the first articulated skeletal remains of the Ogcocephalidae ever recorded as fossils, also representing the oldest members of the family known to date. The general structure of the skeleton of Tarkus gen. nov. provides unambiguous evidence that the existence of the modern ogcocephalid body plan was already established in the early Eocene, and probably originated well before that period. Palaeoenvironmental considerations suggest that Tarkus gen. nov. was a tropical batfish that inhabited the inner-shelf palaeobiotopes of the central-western Tethys.