The discovery of Bulinus (Pulmonata: Planorbidae) in a Miocene palaeolake in the Balkan Peninsula

Large, sinistrally coiled gastropod species have been reported under the genus name Kosovia Atanackovic, 1959 from middle and late Miocene palaeolakes of central Serbia and Kosovo. Despite several papers dealing with the taxonomy and evolution of this genus, its systematic position and possible ancestry have been unresolved. Previously, it has been suggested that it may be a member of the Viviparidae, Lymnaeidae or Planorbidae, but without morphological criteria to support these assertions. In order to elucidate the systematic position of the genus, we investigated type material of the type species Kosovia matejici Pavlovic, 1931, which is the oldest representative and is restricted to middle Miocene deposits of central Serbia. Embryonic shell characters support membership of the Planorbidae. Based on the congruence of all evaluated morphological characteristics, we attribute the species to the genus Bulinus, which makes Kosovia a junior subjective synonym of Bulinus. We discuss potential ancestry of the oldest representative and relationships among the species previously attributed to Kosovia. Our study emphasizes the importance of SEM-based examination of the protoconch to clarify the systematic position of problematic freshwater gastropods, especially when molecular data are absent.