Nouveau Dromaeosauridae, Shanag ashile
theropod from Öösh, Early Cretaceous, Baykhangor Mongolia. American Museum Novitates 3557, 27 pp.
Abstract: A new theropod dinosaur, *Shanag ashile*, from the Early
Cretaceous Öösh deposits of Mongolia is described here. The new
specimen (IGM 100/1119) comprises a well-preserved right maxilla, dentary, and partial splenial. This specimen exhibits a number of derived theropod features, including a triangular anteriorly tapering maxilla, a large antorbital fossa, and maxillary participation in the caudally elongate external nares. These features resemble the Early Cretaceous dromaeosaurids *Sinornithosaurus millenii* and
*Microraptor zhaoianus*, as well as the basal avialan*Archaeopteryx
lithographica*. A comprehensive phylogenetic analysis including 58 theropod taxa unambiguously depicts the new Öösh theropod as a member of Dromaeosauridae. Relative to other dromaeosaurids, *Shanag ashile* is autapomorphic in its lack of a promaxillary fenestra and in the presence of interalveolar pneumatic cavities. The discovery of IGM 100/1119 expands our knowledge of Early Cretaceous dromaeosaurids and the faunal similarity between the Öösh and the Jehol biotas.
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