1. Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan
2. Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
3. Department of Zoology, Kanagawa Prefectural Museum of Natural History, 499 Iryuda, Odawara, Kanagawa 250-0031, Japan
4. Yamashina Institute for Ornithology, 115 Konoyama, Abiko, Chiba 270-1145, Japan
5. The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
6. Institute of Paleontology and Geology, Mongolian Academy of Sciences, 15160 Ulaanbaatar, Mongolia