A new subspecies of Chlamys lioica (Dall) from the Pleistocene Shigarami Formation developed in the environs of Nagano City, central Japan | Monograph of the Mizunami Fossil Museum No. 6

Monograph of the Mizunami Fossil Museum No. 6

A new subspecies of Chlamys lioica (Dall) from the Pleistocene Shigarami Formation developed in the environs of Nagano City, central Japan

Kazutaka Amano and Shigeru Karasawa

MMFM06-003Amano&Karasawa, 1986（PDF 2.64MB）

Amano and Karasawa (1986) print-version

Published: 1986/3/25 　 Page: 41–47, pl. 4

The Neogene deposits are well exposed in the environs of Nagano City. These deposits are stratigraphically subdivided into the Aoki, Ogawa, Shigarami and Sarumaru formations from the lower to upper (Yano and Murayama, 1976). Among them, the Shigarami Formation yields abundant molluscan fossils known as the Shimonireki fauna (Tomizawa, 1958) or the Shigarami fauna (Akiyama, 1962).

Up to this time, a total of four species of Chlamys are known from the Shigarami Formation; Chlamys (Chlamys) tanakai Akiyama, Ch. (Ch.) daishakaensis Masuda and Sawada, Ch. (Ch.) cosibensis (Yokoyama) and Ch. (Ch.) foeda (Yokoyama) (Masuda, 1962, 1986). Besides these species, a new subspecies of Chlamys was obtained from this formation. This new form is much allied to Chlamys lioica (Dall) described and known only from the Pliocene deposits in Alaska. Therefore, it is important to describe this new Chlamys and the relationship between Chlamys lioica and the Shigarami species.