A new alvarezsaurid theropod dinosaur from the Upper Cretaceous of Gobi Desert, Mongolia

Abstract

Ondogurvel alifanovi gen. et sp. nov. (Alvarezsauridae, Parvicursorinae) is described based on a partial postcranial skeleton from the Upper Cretaceous (Campanian) Barungoyot Formation at the Nemegt locality in Mongolia. The new taxon differs from all other alvarezsaurids in having metatarsals II and IV completely fused along their contact area. The phylogenetic analysis places Ondogurvel in a clade with the Late Cretaceous Asian parvicursorines Xixianykus and Albinykus, which have proximally co-ossified metatarsals II and IV. Two morphological types of the parvicursorine carpometacarpus can be recognized. In the first type exemplified by Mononykus and Ondogurvel, the articular surfaces of metacarpals III and IV are located along the lateral margin of the carpometacarpus and small, but functional digits III and IV were flexed in a plane almost perpendicular to the flexion plane of digit II. In the second type exemplified by the Bissekty alvarezsaurid and Linhenykus, the articular surface of metacarpal IV is missing and the articular surface of metacarpal III is located along the distal margin of the carpometacarpus, in line with the distal condyles of metacarpal II. In this case, the small functional digit III was flexing in the same plane as the main digit II. Linhenykus has the carpometacarpus of the second type, but the distal articular surface of metacarpal III is greatly reduced and manual finger III was apparently absent. This drastic difference in the morphology of the carpometacarpus may suggest a deep divergence between the parvicursorine lineages represented by the Bissekty alvarezsaurid – Linhenykus and Mononykus – Ondogurvel.LSID: urn:lsid:zoobank.org:pub:AC4A7F7F-3E67-425A-865F-3F47B0AB2AAE.