1. Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan (e-mail: )
2. Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan
3. Lake Biwa Museum, 1091 Oroshimo-cho, Kusatsu, Shiga 525-0001, Japan