Revision of the type material of the Pliocene species Prolagus bilobus Heller, 1936 (Mammalia, Lagomorpha), with comments on the taxonomic validity of P. osmolskae Fostowicz-Frelik, 2010

The taxonomy of the Pliocene Prolagus in central Europe is still poorly understood. The proven record is limited there just onto P. bilobus from Gundersheim localities (Germany) and P. osmolskae from Raciszyn 1 (Poland). Unfortunately, the taxonomy of P. bilobus has until now remained unclear. Apart from the original description, no studies have provided data based on direct observation of the type material. Only minor attention has also been paid to a detailed analysis of additional material from the Gundersheim localities. Therefore, we are providing the first revision of the type material of P. bilobus accompanied by a synoptic survey of the type locality. Based on previously undescribed material of P. bilobus, we clarify the morphologic variability and dimensional range of P. bilobus, and question the validity of P. osmolskae. A direct revision of the both species evidenced that the only available specimen – the holotype – of P. osmolskae clearly falls within the recorded size and morphological range of the very large P. bilobus. And thus P. osmolskae Fostowicz-Frelik, 2010 is regarded here as a junior subjective synonym of P. bilobus Heller, 1936.