Bulletin of the Mizunami Fossil Museum

Monograph of the Mizunami Fossil Museum No. 6

Anadara (Hataiarca) kakehataensis, a type species of the subgenus Hataiarca is widely distributed in the early Middle Miocene formations deposited in the embaymental conditions on the both sides of Japan and is important element of Arcid-Potamid Fauna (Tsuda, 1965), and of Anadara kakehataensis/ An. Makiyamai Zone (Noda, 1966). The distribution of species is controlled by distinct ecological condition and usually associated with brackish embaymental forms.

This is shown by high percentage of association of Vicaryella notoensis (91%), Cerithideopsilla yatsuoensis (86.4%), Ostrea gravitesta (68.2%), Vicarya yokoyamai (59.1%) and others among 22 localities in the Middle Miocene Kurosedani Formation of Tsuda (1960) (Table 2). The associated species are also examined among the 17 localities in Japan by the frequency of associated species. Crassostrea gravitesta, Cyclina japonica, Hiatula minoensis, Vicarya yokoyamai and Vicaryella notoensis show high percentage in association with Anadara kakehataensis. Anadara kakehataensis is sometimes discussed taxonomically in comparison with Anadara daitokudoensis but the associated molluscan species are slightly different between them in their composition.