[N] 2006 Re-examination of Adasaurus mongoliensis
Kubota, K. & Rinchen, B. (2006) Re-examination of Adasaurus mongoliensis (Dinosauria: Theropoda) from the Upper Cretaceous Nemegt Formation of Mongolia. JVP 26(3) Abstracts pp.88
Adasaurus mongoliensis from the Upper Cretaceous Nemegt Formation of Bugin Tsav, southwestern Mongolia, was described based mainly on pelvic and pedal elements in 1983 and was originally diagnosed by highly reduce pedal ungual II-3. Adasaurus mongoliensis has been referred as a member of dromaeosaurids, but its phylogenetic position within Dromaeosauridae remains unresolved. In this study, its holotype (MPD 100/20, a posterior portion of skull and postcranial skeleton, missing dorsal ribs, forelimbs, and some pedal phalanges) and referred specimens (MPD 100/21, two caudal vertebrae and right foot) are reexamined and compared with other dromaeosaurids.
Preliminary phylogenetic analysis in our study indicates that Adasaurus mongoliensis shows affinities with another Mongolian dromaeosaurid, Velociraptor mongoliensis, in having fused scapulocoracoid and distal tarsals fused with metatarsals. Differences between Adasaurus mongoliensis and Velociraptor mongoliensis are expanded maxillary process of jugal, paroccipital process with straight dorsal edge, and pleurocoels on only anterior sacrals. Adasaurus mongoliensis can be distinguished from other dromaeosaurids in having a low dorsal ridge on median frontals (continuous with sagittal crest on parietals), large surangular foramen, and notched anterior margin of preacetabular process as well as reduced ungual of pedal digit II. Our study suggests that a ventral surface of proximoventral heel on the penultimate phalanx has no asymmetrical ridges like other dromaeosaurids and troodontids (Deinonychosauria), supporting that the use of pedal ungual II-3 is different from that of other deinonychosaur theropods.