Acharax cretacea Kanie and Nishida, 2000

Kiel, Steffen, Amano, Kazutaka & Jenkins, Robert G., 2008, Bivalves from Cretaceous cold-seep deposits on Hokkaido, Japan, Acta Palaeontologica Polonica 53 (3), pp. 525-537 : 527

Acharax cretacea Kanie and Nishida, 2000

Fig. 2C–E .

2000 Acharax cretacea sp. nov.; Kanie and Nishida 2000: 82, fig. 4. 2007 Acharax cretacea Kanie and Nishida ; Jenkins et al. 2007b: fig. 5.8.

Material.—Kanie and Nishida’s (2000) type material was examined in the Yokosuka City Museum; ten newly collected specimens from the Yasukawa seep site.

Discussion.—Kanie and Nishida (2000: 83) suggested the presence of a long external ligament. A newly collected small specimen from the Yasukawa seep site shows that the ligament is external and rather short ( Fig. 2D 1 ). Another specimen from this site shows the prismatic shell microstructure ( Fig. 2E ), typical for solemyids.

Stratigraphic and geographic range.—Cenomanian sulfiderich sediments (own observation) and Campanian seep carbonates of the Yezo Group on Hokkaido, Japan.

Figures

Fig. 2. Solemyid bivalves from Cretaceous cold seep deposits on Hokkaido, Japan. A, B. Acharax mikasaensis sp. nov., from the Albian Ponbetsu site in Mikasa City. A. Paratype (UMUT MM 29523) showing external sculpture, dorsal (A1) and lateral (A2) views. B. Holotype (UMUT MM 29524) showing features of the shell interior; arrow in B1 indicates posterior adductor muscle scar, B2 shows a dorsal view, white arrow in B3 indicates the anterior adductor muscle scar, black arrow indicates the narrow band that ascends from its posteroventral margin. C–E. Acharax cretacea Kanie and Nishida, 2000, from the Campanian Yasukawa site. C. Right valve of a slightly deformed, medium−sized specimen (UMUT MM 29525), length 34 mm.D. Small specimen (UMUT MM 29526) (length 8 mm) showing the rounded posterior shell margin, dorsal (D1) and lateral (D2) views. E. Cross section of shell showing the prismatic microstructure.

Fig. 1. Maps showing the fossiliferous seep deposits. A. The Albian Ponbetsu site. B. The Campanian Yasukawa and Omagari sites. C. The Cenomanian Kanajirisawa site. D. Overview.