Our love for Will Downs cannot be easily expressed in a few words. Will made a profound impact in Chinese vertebrate paleontology at a time of maximum stress as the Chinese scientific communities struggled to find their footing amid rapid changes of research environment and science policy during the early days of economic reforms of the country. Besides being one of the few western scientists who could read technical Chinese paleontological literature, Will inspired us with his single-minded dedication to field paleontology, his love of adventure, his care for Chinese culture, and his tireless promotion of Chinese vertebrate paleontology. Those of us who were privileged to enjoy many field seasons with Will Downs will forever marvel at his great sense of humor and unique blend of optimism and carefree attitude.
We thank numerous persons who have made valuable contributions in collecting the specimens described herein and in establishing the stratigraphic framework: Will Downs, L. Flynn, E. Lindsay, B. Engesser, D. Oppliger, C. Mödden, P. Heller, N. Opdyke, Xie Junyi, Xie Guangpu, Yue Leping, Wu Ruijin, Zhang Liren, Chen Shanqin, Feng Wenqing, and Gao Wei. We are grateful to R. Tedford who has been a consistent sponsor and advisor on the Lanzhou project and serves as an excellent sounding board for both stratigraphic and systematic issues. Discussions with P.D. Polly, J.C. Barry, and A.V. Lavrov helped to clarify hyaenodont systematics. Furthermore, Barry kindly allowed us to examine unpublished Hyainailouros materials from Pakistan. We appreciate the detailed reviews by J. Baskin and Barry, which greatly improved both the language and the substance of this paper. Field and laboratory research was supported by grants from the Chinese National Natural Science Foundation to Wang (40128004) and Qiu (49872011). International travel was supported by National Geographic Society (6771-00; 6004-97; 5527-95) and James Carter Fund, American Museum of Natural History.