ИСТИНА

Recent study of Late Jurassic ophthalmosaurid ichthyosaurs revealed a number of new taxa. However, the validity of several taxa from the Volgian (latest Jurassic-earliest Cretaceous) of European Russia still remains unclear, complicating comparisons and, in some cases, affecting taxonomic decisions. A revision of type specimens of Undorosaurus Efimov, 1999 reveals the potential validity of four species within Undorosaurus: U. gorodischensis, U. nessovi, U. trautscholdi, and U. kielanae. Furthermore, examination of the holotype of Cryopterygius kristiansenae from the coeval strata of the Svalbard archipelago shows that this taxon is a junior synonym of Undorosaurus gorodischensis. This supports the idea of faunal exchange between the Middle Russian Sea and other Boreal seas in the Late Jurassic. A new phylogenetic dataset including 33 taxa and 102 characters, 21 of which are new, was composed in order to resolve the phylogenetic position of Undorosaurus. The results of this analysis challenge all previous phylogenetic hypotheses for Ophthalmosauridae in a number of aspects, including the recovery of Undorosaurus spp. as deeply nested within Platypterygiinae as a sister group to derived platypterygiines.