Multituberculate mammal of possible North American affinity in the Maastrichtian of the Russian Far East

An isolated fragment of a multituberculate lower premolar (p4) from the Upper Cretaceous (Maastrichtian) Udurchukan Formation at Kundur locality, Amur oblast, Far East of Russia, is the only multituberculate known from Russia. This tooth shares notable similarities with the p4 of the eucosmodontid Stygimys from the Maastrichtian-Palaeocene of North America, as evidenced by its straight dorsal margin in lateral profile, low crown above the distal root, prominent V-shaped distolabial cusp, absence of lingual ridges for the two distalmost serrations, and distinctive interradicular crest. This tooth can be provisionally attributed to Eucosmodontidae. The remaining components of the Kundur vertebrate assemblage, comprising the hadrosaurids Kundurosaurus and Olorotitan, nodosaurid ankylosaurs, and ornithomimid theropods also exhibit North American affinities. The Kundur vertebrate assemblage may represent a common Asiamerican fauna that lived in the Late Cretaceous in Northeast Asia and Western North America (Laramida).