Adasaurus mongoliensis, meaning Ada's lizard, is a small theropod dinosaur described and named in 1983 by Rinchen Barsbold. Ada is a Mongolian mythological character considered to be an evil spirit, and this Dromaeosaurid dinosaur certainly could be considered an evil looking animal. Unfortunately the relationships of Adasaurus and other Dromaeosaurids are not well understood because Adasaurus is represented by fragmentary fossils of the skull as well as post-cranial skeleton. These fragments, however, have lead to the idea that Adasaurus should be considered a member of the subfamily that includes Dromaeosaurus and Utahraptor, the Dromaeosaurinae. These are heavily built members of the family. Conversely the animal is shown to be a part of the Velociraptorinae subfamily which consists of smaller and more gracile members of the family.