Mosasaurs (Squamata: Mosasauridae) from the Upper Cretaceous of the Southern Urals.

The study of new finds of mosasaurids from the Izhberda locality (Southern Urals, Orenburg Region) has made it possible to record for the first time the presence of mosasaurs from the subfamilies Mosasaurinae, Tylosaurinae, and Plioplatecarpinae from the Upper Cretaceous of the Orenburg Region, including representatives of the genera Mosasaurus, Prognathodon, and Clidastes, which are known from the Upper Cretaceous of North America and Western Europe. Of interest is the discovery of the tylosaurine Taniwhasaurus, previously known from New Zealand, Antarctica, South Africa, and Japan. Therefore, the Campanian mosasaurid fauna of the Southern Urals is intermediate and includes North American–European and Asia–Pacific taxa. However, all the finds of mosasaurs from the Izhberda locality can only be identified in open nomenclature, which makes detailed comparisons of the faunas difficult. Revision of the type series of mosasaur Liodon rhipaeus Bogolyubov, 1910 from the Southern Urals has allowed us to conclude that, in addition to the three mosasaurian vertebrae, it includes the ischium and posterior fragment of the mandible of a plesiosaur. Liodon rhipaeus is clearly a nomen dubium and the vertebrae of its type series cannot be identified more precisely than Tylosaurinae indet. [ABSTRACT FROM AUTHOR]