1. Department of Geology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
2. Numata Fossil Museum, 2-7-49, Minami 1, Numata town, Hokkaido, 078-2225 Japan
3. Hokkaido University Museum, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-0810 Japan
4. Departments of Paleobiology and Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC, USA