New Data on Hesperornithids (Aves: Ornithurae) from the Campanian of the Lower Volga Region (Late Cretaceous, Russia).

Taxonomic diversity of Late Cretaceous hesperornithids (Aves: Hesperornithidae) of European Russia and Eastern Europe as a whole remain poorly understood, and the morphology of these large flightless birds is poorly known. New finds of Hesperornithidae in the Karyakino locality (Saratov oblast, Russia) confirm the coexistence of two forms of these flightless seabirds in the Campanian (mid-Late Cretaceous) of the Lower Volga region. A femur is described for the first time for Hesperornis rossicus Nessov et Yarkov, 1993, indicating that this large species is morphologically distinct from North American H. regalis Marsh, 1872.