A new dromaeosaurid theropod from Ukhaa Tolgod (Ömnögov, Mongolia) ; American Museum novitates, no. 3545

Abstract

We describe a new dromaeosaurid theropod from the Upper Cretaceous Djadokhta Formation of Ukhaa Tolgod, Mongolia. The new taxon, Tsaagan mangas, consists of a well-preserved skull and cervical series. This specimen marks only the second dromaeosaurid taxon from a formation that has otherwise yielded numerous specimens of Velociraptor mongoliensis, and Tsaagan mangas is the only dromaeosaurid known from Ukhaa Tolgod beyond sporadic occurrences of isolated teeth. Tsaagan mangas differs from other dromaeosaurids in the possession of a straight, untwisted, and pendulous paroccipital process, a large and anteriorly located maxillary fenestra, and a jugal-squamosal contact that excludes the postorbital from the margin of the infratemporal fenestra. The phylogenetic affinities of Tsaagan mangas are determined through a comprehensive phylogenetic analysis of Coelurosauria, confirming its position within Dromaeosauridae. This new specimen, coupled with CT imaging, provides new information on the skull and braincase anatomy of dromaeosaurids.