New Genus of Primitive Ocean Sunfish with Separate Premaxillae from the Eocene of Southwest Russia (Molidae, Tetraodontiformes)

Abstract

The upperjaws of a fossil fish from the late Eocene of Russia (Kumsky Horizon, North Caucasus) are referred to the Molidae because of their uniquely derived features of highly striated external bone surfaces and laterally elongate trituration teeth, as well as overall morphological similarity to the upper jaws of molids. However, the Eocene upper jaws differ from those of all other fossil (previously known only from the Miocene and Pliocene) and extant molids by having the premaxillae separate and articulated medially by interdigitating processes (versus fused in the midline). The separation of the premaxillae in the new genus and species, Eomola bimaxillaria, is a retention of the plesiomorphic condition found in triodontids and tetraodontids.