New material and diagnosis of a new taxon of alvarezsaurid (Dinosauria, Theropoda) from the Upper Cretaceous Bissekty Formation of Uzbekistan

ABSTRACT

A new alvarezsaurid theropod, Dzharaonyx eski, gen. et sp. nov., is documented by a variety of dissociated but well-preserved postcranial bones from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. It has opisthocoelous posterior dorsal vertebrae lacking infrapostzygapophyseal fossae. The posterior caudal vertebrae are procoelous and have a longitudinal canal within the neural arch. The humerus is intermediate in structure between those of the Argentinian alvarezsaurid Patagonykus and the Mongolian parvicursorine Mononykus in having a small internal tuberosity, similar-sized radial and ulnar condyles, a distally protruding radial condyle, and a greatly reduced entepicondyle. The ulna has a hypertrophied olecranon process, a globular carpal trochlea, and a facet for the aponeurosis tubercle of the radius. On the carpometacarpus, the articular surface of metacarpal III is in line with the distal articular joint of metacarpal II. On manual phalanx II-1, the flexor ridges are similarly developed and the dorsolateral process and the ‘hook-like’ ventrolateral process are absent. The collateral grooves on manual ungual phalanx II-2 are either partially open or completely enclosed to form ventral foramina. The pubis bears a preacetabular tubercle. The pes is arctometatarsalian. Metatarsal II forms a posterolateral flange. Pedal phalanx IV-1 has a protruding proximomedial process, a proximoventral notch, and asymmetrical distal condyles. The flexor tubercles on the pedal ungual phalanges are small. Phylogenetic analysis found Dzharaonyx within Parvicursorinae in a polytomy with other Asiatic taxa. Dzharaonyx is the most plesiomorphic and geologically oldest member of Parvicursorinae known to date.

ACKNOWLEDGMENTS

The laboratory research by AOA received support from the Russian Science Foundation (19-14-00020) and the Zoological Institute, Russian Academy of Sciences (project 1021051302397-6). We thank two anonymous reviewers for their reviews of the manuscript.