A large alvarezsaurid from the late Cretaceous of Mongolia. (American Museum novitates, no. 3648)

Abstract

We report a new alvarezsaurid, Kol ghuva, from the late Cretaceous of Mongolia that demonstrates that the clade was not restricted to small taxa (~3-15 kg). The specimen was found at the Ukhaa Tolgod locality, which has previously produced only a single diminutive alvarezsaurid, Shuvuuia deserti. Although known only from a well-preserved right foot, the new taxon is diagnosable by the following combination of characters: extensor grooves on digit IV phalanges; robust flexor tubercle on pedal unguals; MT III does not reach ankle; accessory dorsomedial flange absent on the medial side of the distal end of the MT II; MT II shorter than MT IV; and MT III extends higher proximally than other alvarezsaurids (more than K total metatarsus length). The new taxon provides additional insight into the diversity of this clade and the dinosaurian assemblage of Ukhaa Tolgod.