New record of Hesperornis rossicus (Aves, Hesperornithiformes) in the Campanian of Saratov Province, Russia

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New materials of Hesperornis rossicus Nessov et Yarkov, 1993 (one complete and one fragmentary tarsometatarsus) from the lower Campanian Karyakino locality in Saratov Province, Russia, show for the first time distal tarsometatarsal morphology for this species and allow reconsideration of its diagnosis. H. rossicus is the most derived species of the genus, having the greatest size for the genus and strongly reduced inner fingers, with undivided trochlea on tarsometatarsus for digits II and III and condyle for digit II completely behind that of digit III. Previous records of Hesperornis sp. from Rychkovo and Hesperornithidae indet. from Bereslavka (both Volgograd Province, Russia) are referred here to H. rosslcus.