Previously unpublished trionychid turtle material from the Upper Cretaceous (Santonian–lower Campanian) Bostobe Formation from the Baybishe and Baykhozha localities in Kazakhstan is described. The material represents a new  species of Khunnuchelys, a large, skull-based clade of Cretaceous Asian trionychids. Concordant with other partial skulls and fragmentary specimens described previously, Khunnuchelys lophorhothon sp. nov. has the unusual features of a beaklike maxilla and a vaulted, expanded triturating surface. In addition, the specimens reveal novel features including a constricted skull roof. Although estimates of the length of the carapace differ depending on estimation method, the skull belonged to a turtle of comparable size to the shell-based species “Trionyx” kansaiensis from the same formation. It is likely that K. lophorhothon and “T.” kansaiensis are synonymous, but this can be proved only by a find of associated skull and shell material.

Key words: Testudines, Trionychidae, Trionychia, Khunnuchelys lophorhothon, Cretaceous, Kazakhstan.

Igor G. Danilov [igordanilov72@gmail.com] and Alexander O. Averianov [dzharakuduk@mail.ru], Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb. 1, 199034, St. Petersburg, Russia; Natasha S. Vitek [nsvitek@utexas.edu ], Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USA; Vadim N. Glinskiy [vadim.glinskiy@gmail.com], Department of Paleontology, Geological Faculty, St. Petersburg State University, Universitetskaya Emb. 7/9, 199034, St. Petersburg, Russia.