Abstract
The Shimosato Formation comprises the lower part of the Kumano Group of the southeastern Kii Peninsula, southwestern Honshu. It yields such mollusks as Saccella miensis (Araki), Cyclocardia siogamensis (Nomura), Macoma (Macoma) izurensis (Yokoyama), Cultellus izumoensis Yokoyama, Dosinia (Phacosoma) nomurai (Otuka), Periploma (Aelga) mitsuganoense Araki, Thracia watanabei ltoigawa and Shibata, Turritella (Hataiella) sagai Kotaka, and Fulgoraria (Musashia) yanagidaniensis Araki. The Periploma-Saccella-Cyclocardia and Turritella-Dosinia assemblages of the Shimosato Formation are inferred to represent lower sublittoral to bathyal and sublittoral environments, respectively. The fauna of the Shimosato Formation is comparable with the subtropical Akeyo Fauna of late Early Miocene age, based on the occurrence of diagnostic species such as Dosinia (Phacosoma) kawagensis Araki, Thracia watanabei ltoigawa and Shibata, Turritella sagai, and Fulgoraria yanagidaniensis. The assemblages of the middle part of the Shikiya Formation and the lower part of the Mitsuno Formation are comparable with those of the tropical Kurosedani (subtropical Kadonosawa) Fauna of latest Early to earliest Middle Miocene age.
