The first record of the halitheriine dugongid (Sirenia: Dugongiade) in the western North Pacific Ocean - 1992
Steller's sea-cow (Sirenia: Hydrodamalis gigas) from the Middle Pleistocene Mandano Formation of the Boso Peninsula, Central Japan - 1994
Steller's sea-cow (Hydrodamalis gigas) in the Bearing Island, Kamschatka - 1995
New material of sirenian fossil from the upper Miocene of Numata-cho, Hokkaido, Japan - 1996
A mysticete fossil from the middle Pleistocene Ichijiku Formation, Chiba Prefecture, Japan - 2004
Discovery of a skeleton of the Hydrodamalis sea cow from the Lower Pleistocene Iimuro Formation, Koame City, Tokyo, central Japan - 2007
A balaenopterid skull (Order Cetacea) from the Early Pleistocene of Kuromatsunai, Hokkaido, Japan - 2010