A new skeleton of the late Oligocene Enspel cormorantaEurofrom Oligocorax to Borvocarbo, and back again

A new specimen of the cormorant species from the late Oligocene (MP 28) fossil site Enspel in Germany-the third to be discovered at this site-is described. Previously unknown or controversial features bearing on the taxonomic and phylogenetic affinities of this bird are identified, which do not support the assignment of the Enspel cormorant to the taxon Borvocarbo. The species is therefore here, tentatively, transferred back to Oligocorax, in which it was first placed. The new osteological data confirm that ?Oligocorax stoeffelensis is a stem group representative of Phalacrocoracidae, and the species exhibits a previously unrecognised derived morphology of the pectoral girdle bones in that the furcula is fused with the apex carinae of the sternum, a feature absent in modern cormorants. A phylogenetic analysis revealed two alternative positions for ?O. stoeffelensis relative to other stem group Phalacrocoracidae, supporting a sister group relationship either to the clade including Nambashag, Nectornis and crown group Phalacrocoracidae or to a clade including ?O. stoeffelensis and crown group Phalacrocoracidae to the exclusion of Nambashag and Nectornis.