The first dromaeosaurid (Dinosauria: Theropoda) from the Lower Cretaceous Bayan Gobi Formation of Nei Mongol, China

Michael Pittman; Rui Pei; Qingwei Tan; Xing Xu

doi:10.7717/peerj.1480

The first dromaeosaurid (Dinosauria: Theropoda) from the Lower Cretaceous Bayan Gobi Formation of Nei Mongol, China

PeerJ. 2015 Dec 7:3:e1480. doi: 10.7717/peerj.1480. eCollection 2015.

Authors

Michael Pittman¹, Rui Pei¹, Qingwei Tan², Xing Xu³

Affiliations

¹ Vertebrate Palaeontology Laboratory, Department of Earth Sciences, The University of Hong Kong , Pokfulam , Hong Kong, China.
² Long Hao Institute of Geology and Paleontology , Hohhot, Nei Mongol , China.
³ Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology & Paleoanthropology, Chinese Academy of Sciences , Beijing , China.

Abstract

The first dromaeosaurid theropod from the Lower Cretaceous Bayan Gobi Formation is identified based on an incompletely preserved partially-articulated left leg, increasing the known diversity of its understudied ecosystem. The leg belongs to specimen IVPP V22530 and includes a typical deinonychosaurian pedal phalanx II-2 with a distinct constriction between the enlarged proximal end and the distal condyle as well as a typical deinonychosaurian enlarged pedal phalanx II-3. It possesses a symmetric metatarsus and a slender and long MT V that together suggest it is a dromaeosaurid. Two anatomical traits suggest the leg is microraptorine-like, but a more precise taxonomic referral was not possible: metatarsals II, III and IV are closely appressed distally and the ventral margin of the medial ligament pit of phalanx II-2 is close to the centre of the rounded distal condyle. This taxonomic status invites future efforts to discover additional specimens at the study locality because-whether it is a microraptorine or a close relative-this animal is expected to make important contributions to our understanding of dromaeosaurid evolution and biology. IVPP V22530 also comprises of an isolated dromaeosaurid manual ungual, a proximal portion of a right theropod anterior dorsal rib and an indeterminate bone mass that includes a collection of ribs. Neither the rib fragment nor the bone mass can be confidently referred to Dromaeosauridae, although they may very well belong to the same individual to whom the left leg belongs.

Keywords: Balongwula; Bayan Gobi Formation; Deinonychosaur; Dromaeosaurid; Lower Cretaceous; Microraptorine; Nei Mongol; Paravian; Theropod.

Grants and funding

The collection and study of IVPP V22530 was supported by funds awarded to XX by the National Science Foundation of China (41120124002) and the Bureau of Land and Resources of Bayan Nur. Study of IVPP V22530 was also supported by funds awarded to MP by the Research Grant Council’s General Research Fund (17103315). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.