New material of a troodontid theropod (Dinosauria: Saurischia) from the Lower Cretaceous of Mongolia

Abstract

New material of a troodontid theropod from Khamaryn Ar in Mongolia, representing the second troodontid specimen described from the Lower Cretaceous of the Gobi Basin, is reported. This material consists mainly of caudal, manual and pedal bones, and can be assigned to Troodontidae based on the presence of derived features such as distal caudals bearing sulci on neural arches instead of neural spines, asymmetrical pes with slender metatarsal II and robust metatarsal IV, and pedal phalanx II-2 with the distal articular surface less than half the size of the proximal surface. The present specimen is considered merely as Troodontidae gen. et sp. indet. because of the lack of definitive autapomorphies. The present finding suggests that further exploration of the Lower Cretaceous in the Gobi Basin may still provide much new information on the theropod fauna in this region.

Keywords::

• Theropoda
• Troodontidae
• Gobi Basin

Acknowledgements

We are grateful to K. Hayashibara (former president of the Hayashibara Company Limited, Okayama, Japan) for his continuous financial support to the Japanese–Mongolian Joint Paleontological Expedition since 1993. Thanks are also due to the Japanese and Mongolian members of the joint expedition team for their help in the field and laboratories. Olympus, Mitsubishi Motor Company, and Panasonic supplied equipment for the expedition. We are grateful to X. Xu (IVPP) and R. Irmis and C. Levitt-Bussian (UMNH) for access to specimens under their care. We thank M. Manabe (National Museum of Nature and Science, Tokyo) for access to the CT scan facility under his care. S. H. was supported by the Sasakawa Scientific Research Grant from The Japan Science Society. TNT was freely available, thanks to a subsidy from the Willi Hennig Society. Two anonymous reviewers made constructive suggestions that improved the clarity of the manuscript. Finally, we thank editors of this volume for inviting us to contribute the present paper for celebrating the on-going career of Yuki Tomida. This paper is the Japanese–Mongolian Joint Paleontological Expedition Contribution Number 86.

Disclosure statement

No potential conflict of interest was reported by the authors.