New data on the earliest European ruminant (Mammalia, Artiodactyla): A revision of the fossil mandible from Rusce in the Pcinja basin (late Eocene, Southeastern Serbia)

A fragmented right branch of a ruminant mandible from Rusce (Pcinja basin, Serbia) was originally published in the first half the twentieth century as Micromeryx flourensianus, a small ruminant common in the middle Miocene of Europe. Based on this determination, sedimentary filling of the Pcinja basin was considered to be of late Miocene age. However, later paleobotanical and micromammalian studies pointed to a late Eocene age for these deposits. The redescription and discussion of the ruminant fossil mandible from Rusce led to the conclusion that the specimen may belong to a small species of Bachitheriidae, probably to Bachitherium thraciensis. This ruminant was originally only known from late Eocene strata in Bulgaria. The peculiar late Eocene faunal composition from the Balkans (e.g., rodents, perissodactyls, and ruminants) confirms that the "Balkanian High" was a distinct paleobiogeographical province from that of Western Europe until the Bachitherium dispersal event, which occurred during the early Oligocene ca. 31 Mya.