right pelvic girdle comprising the ilium, ischium and pubis. A second specimen is represented by the less complete paratype MPC-D 100/21 that includes two caudal vertebrae and a nearly complete right foot. Both specimens were unearthed from the Nemegt Formation at the locality of Bügiin Tsav, in the Gobi Desert of Mongolia. In 2004, Philip J. Currie and David J. Varricchio referred another two specimens to Adasaurus labelled as IGM 100/22 and IGM 100/23. Supposedly, the specimens were recovered from the same locality of the holotype. However, these specimens are actually known from the Shine Us Khuduk and Tel Ulan Chaltsai localities (respectively) of the Bayan Shireh Formation and thus, they are older than the remains of Adasaurus from the younger Nemegt Formation. They represent a different and new taxon that differs from Adasaurus. Description Adasaurus was a rather large-sized dromaeosaurid. The holotype has an estimated length of with a weight of . The comparatively larger pedal elements of the paratype indicate a gently bigger size in this latter specimen which is estimated around long and in body mass. Aside from the reduced pedal ungual II, Adasaurus can be recognised by the following additional traits: expanded projection of the maxillary; recurved lacrimal; lower jaw with a prominent surangular foramen; irregular triangular projection on the quadrate shaft; pleurocoels are present on the anterior sacral vertebrae; and the anterior border of the anterior blade in the ilium is relatively shortened. Skull On the right side of the skull, the lower portion of the jugal is expanded from the top to the bottom. The quadrate is a large and vertical bone with a large triangular projection on its lateral border. This triangular projection is located on the quadrate shaft and bent to the top. The top surface of the right ectopterygoid—a smalle bone of the palate—is flattened to the palate. As in other dromaeosaurids, the lacrimal has an inverted L-shape, but the thin body of this bone is curved, which is also seen in Austroraptor. Skeleton The scapula and coracoid of the holotype are completely fused giving form to the scapulocoracoid, and the suture between them is not present. Pneumatic foramina are present in the holotypic anterior sacral vertebrae. The femur and tibia of the holotype measure and long, respectively, and the fourth trochanter is a prominent and rugose ridge that is located on the posterior inner surface of the upper region of