Brackish-Water Ostracoda (Crustacea) from the Obitsu River Estuary, Central Japan

The brackish-water ostracod fauna was surveyed for almost two years at 17 points representing typical environments, such as foreshore sand flat, back marsh, and tidal creek, in the intertidal zone of the Obitsu River Estuary, Chiba Prefecture, central Japan. Twenty-one species belonging to 17 genera and 10 families were identified. In addition to the description of one new genus, Palusleptocythere, and four new species, Pontocythere xiphoidea, Palusleptocythere migrans, Loxoconcha kosugii, and Cytherois ikeyai, chitinous parts are described for the first time for four previously described species, Spinileberis pulchra Chen, 1982, Angulicytherura ? miii (Ishizaki, 1969), Semicytherura wakamurasaki Yajima, 1982, and Loxoconcha pulchra Ishizaki, 1968. Furthermore chitinous parts of male Dolerocypria mukaishimensis Okubo, 1980 are also shown for the first time. This is the first report on an ostracod fauna from a shallow estuarine environment in either Japan or any adjacent area.