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 ½ total metatarsus length). The new taxon provides additional insight into the diversity of this clade and the dinosaurian assemblage of Ukhaa Tolgod.
Highlights
Alvarezsaurids have been recognized only relatively recently as a distinct group of theropod dinosaurs (Bonaparte, 1991; Perle et al, 1993; Novas, 1996, 1997; Chiappe et al, 1996, 1998; Hutchison and Chiappe, 1998)
Kol ghuva is similar to the oviraptorosaur Avimimus portenosus that is present in Djadoktha and Barun Goyot localities in the Gobi Desert (Kurzanov, 1981, 1987; Watabe et al, 2006)
The proximal ends of MT II and IV are clearly not ossified in Kol ghuva
Summary
Alvarezsaurids have been recognized only relatively recently as a distinct group of theropod dinosaurs (Bonaparte, 1991; Perle et al, 1993; Novas, 1996, 1997; Chiappe et al, 1996, 1998; Hutchison and Chiappe, 1998). Late Cretaceous of Mongolia, which repre¬ sents a new alvarezsaurid taxon This unique specimen (IGM 100/2011, field number MAE 00-45) is represented by a complete articulated left pes from the Ukhaa Tolgod locality (Dashzeveg et al, 1995; Dingus et al, 2008) in the south central Gobi Desert. There is no evidence that metatarsal III reached the proximal end of the metatarsus near the ankle joint, this is present only in alvarezsaurids more derived than Alvarezsaurus calvoi and Patagonykus puertai (Chiappe et al, 1998, 2002). Most theropods have two distal tarsals (Norell and Makovicky, 1999); in all alvarezsaurids that preserve this region (Patagonykus puertai MCF PVPH-37, Shuvuuia deserti IGM 100/1001, and Parvicursor remotus [Karhu and Rautian, 1996]) only a single ovoid element is present (Chiappe et al, 2002).
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