|Class||Chordata, Reptilia, Dinosauria, Theropoda, Dromaeosauridae, Dromaeosaurinae|
|Name Translation||Ada's Lizard|
|Period||Campanian to Maastrichtian (Cretaceous)|
|Size||1.8 meters long|
Adasaurus ( /ˌɑːdəˈsɔrəs/ ah-də-sawr-əs; "Ada's lizard") is a genus of dromaeosaurid theropod dinosaur from the Late Cretaceous Period of what is now Central Asia. It was a small bipedal carnivore with a sickle-shaped claw on the second toe of each hind foot. An adult was perhaps about 1.8 m (5.9 ft) long.
Ada is an evil spirit in the national mythology of Mongolia. The name also includes the Greek word sauros meaning 'lizard', the most common suffix used in dinosaur names. There is one species (A. mongoliensis), named after the country of Mongolia, where the fossil was found. Both genus and species were named and described in 1983 by famous Mongolian paleontologist Rinchen Barsbold.
Adasaurus is a member of Dromaeosauridae, a theropod family thought to be very closely related to birds. Relationships within the family are poorly understood, but Adasaurus seems to be a member of the subfamily Dromaeosaurinae, along with the Mongolian Achillobator and several North American species.Other dromaeosaurids include Deinonychus, Velociraptor, Microraptor, and Buitreraptor. Adasaurus is unique among dromaeosaurids in having much smaller sickle-claws on its hind feet.
Two specimens of Adasaurus have been found, both from the Nemegt Formation of Bayankhongor Province in Mongolia. The holotype, IGM 100/20, is an incomplete skeleton with partial skull, including the vertebral column except the back of the tail, all three bones of the pelvis, the shoulder girdle and the hindlimbs. The second specimen, the paratype IGM 100/51 also described in the original paper, consists of the back end of another skeleton, including the hindlimbs. Both specimens are currently in the collection of the Mongolian Geological Institute in Ulaanbaatar, Mongolia.
The age of the Nemegt, like most of Mongolia's Late Cretaceous sediments, is not known for certain, but it is commonly thought to belong to the Maastrichtian stage of the Late Cretaceous Period.Therefore the Nemegt was deposited somewhere between 74 and 65 million years ago. Other dinosaurs found in this formation include Tarbosaurus, Anserimimus, and Saurolophus.