New finds of hesperornithids in the European Russia, with comments on the systematics of Eurasian Hesperornithidae

Аннотация

New remains of Hesperornithidae are described from several Late Cretaceous (Campanian) localities of the Lower Volga Region (European Russia). New specimens from Rychkovo and Karaykino localities cannot be referred to as Hesperornis rossicus Nessov et Yarkov, 1993 and likely represent a new undescribed species. Bones from Rychkovo belonged to immature individuals with an incompletely formed tarsometatarsus, which is comparable in size to those of adults known from Karyakino. A tarsometatarsus from the Malaya Rybka locality belongs to a smaller hesperornithiform species and represents the first avian record in this locality. An even smaller hesperornithiform from the Bereslavka locality resembles Asiahesperornis bazhanovi Nessov et Prizemlin, 1991. We discuss the systematics of Eurasian hesperornithiforms. We adhere to the validity of Hesperornis rossicus and doubt of the assignment to this species of Swedish materials. Asiahesperornis bazhanovi is undoubtedly a separate valid taxon of hesperornithiforms, but the generic name Asiahesperornis Nessov et Prizemlin, 1991 may be a junior synonym of Parahesperornis Martin, 1984.