Alvania” akibai ( Yokoyama, 1926 )

Hasegawa, Kazunori, 2022, Bathyal Rissoidae (Gastropoda: Rissooidea) off the Russian Far East coast of the Sea of Japan, with redescription of Punctulum reticulatum Golikov, 1986, Ruthenica, Russian Malacological Journal 32 (2), pp. 85-92 : 87

“ Alvania” akibai ( Yokoyama, 1926)

( Fig. 2A )

Rissoa (Alvania) akibai Yokoyama, 1926: 275 , pl. 34, fig. 3 (see Hasegawa [2014] for more detailed synonymy).

Material examined. SoJaBio A 2-10, MIBM 39336 ( Fig. 2A ); SoJaBio B 6-7, MIBM 14492; SoJaBio B 7-7, MIBM 39342 [depth range: 455–1011 m].

Additional material examined (cited from Hasegawa, 2014). ZIN, non-registered, off Primorsky Krai, 44°48.5’N, 136°46.0’E, 373–494 m (voucher specimen of Punctulum sp. fide Golikov et al., 2001: 158) .

Distribution. Off Primorsky Krai coast on the northern slope, and from Musashi Bank to off Shimane Prefecture on the southeastern slope in the Sea of Japan, within the depth range of 220–1011 m.

Remarks. This species was originally described based on fossils from the Pliocene Sawane Formation on Sado Island in the Sea of Japan, and is characterized by the peculiar pockmarked protoconch sculpture [ Hasegawa, 2014: fig. 37D]. Its previously known vertical distribution range was 220–635 m, and that is significantly extended to 1011 m in the present study.

Figures

FIG. 2. Species of Rissoidae. A. Punctulum akibai (Yokoyama, 1926), SoJaBio stn. A2-10 (455-456 m), MIBM 39336. B. Punctulum nihonkaiensis (Hasegawa, 2014), SoJaBio stn. A2-10 (455-456 m), MIBM 39337. C-D. Frigidoalvania asura (Yokoyama, 1926), SoJaBio stn. B7-7 (470-528 m), MIBM 39340. E-F. Frigidoalvania tanseimaruae Hasegawa, 2014, SoJaBio stn. B6-7 (1,001-1,011 m). G-J. Punctulum flavum (Okutani, 1964); G-H, “shallow-water form”, SoJaBio stn. A2-10 (455-456 m), MIBM 14270; I-J, “deep-water form”, SoJaBio stn. A6-7 (2,511-2,534 m), MIBM 39334. All at the same scale; scale = 1 mm. РИС. 2.Виды Rissoidae.A. Punctulum akibai (Yokoyama,1926), SoJaBioст.A2-10 (455-456м), MIBM 39336.B. Punctulum nihonkaiensis (Hasegawa, 2014), SoJaBio ст. A2-10 (455-456 м), MIBM 39337. C-D. Frigidoalvania asura (Yokoyama, 1926), SoJaBio ст. B7-7 (470-528 м), MIBM 39340. E-F. Frigidoalvania tanseimaruae Hasegawa, 2014, SoJaBio ст. B6-7 (1001-1011 м). G-J. Punctulum flavum (Okutani, 1964); G-H, “мелководнаЯ форма”, SoJaBio ст. A2-10 (455-456 м), MIBM 14270; I-J, “глубоководнаЯ форма”, SoJaBio ст. A6-7 (2511-2534 м), MIBM 39334. Все раковины в одном масШтабе, масШтабнаЯ линейка = 1 мм.