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The remains of a choristodere recently discovered at Two Volcanoes, a new locality in the Gobi Desert of Mongolia, are described in this paper. Consisting of a fairly complete skull and partial postcranial skeleton, this specimen represents a new species of the genus Tchoiria. The new species differs from Tchoiria namsarai in having a much smaller number of teeth. Several elements preserved in this specimen are unknown in T. namsarai and thus provide new information about the genus. Phylogenetic analysis with the addition of data from the new specimen confirms the basal position of Tchoiria in Simoedosauridae.