1995 年 1995 巻 177 号 p. 65-78
Sixty-six species in 44 genera of fossil ostracodes are reported for the first time from the lower Middle Miocene Suenomatsuyama Formation, distributed in Ninohe City, Iwate Prefecture, Northeast Japan. Dominating species throughout the formation are Elofsonella cf. concinna (Jones), Neomonoceratina japonica (Ishizaki), Pectocythere daishakaensis Tabuki and Schizocythere kishinouyei (Kajiyama). Vertical changes of species composition of ostracode faunas and Q-mode cluster analysis reveal that the lower part of the Suenomatsuyama Formation is dominated by cool and sublittoral species, while the middle to upper part is marked by sublittoral temperate-water species. Thus, cool to temperate water ostracode species, which appeared abundantly in the middle part of the underlying Kadonosawa Formatiton, lingered on until the deposition time of the Suenomatsuyama Formation, whereas warm-water species became dominant in the upper part. One new species, Laperousecythere ishizakii, is described herein.
