Bathyacmaea cf. subnipponica Sasaki, Okutani, and Fujikura, 2003

Kaim, Andrzej, Jenkins, Robert G. & Hikida, Yoshinori, 2009, Gastropods from Late Cretaceous Omagari and Yasukawa hydrocarbon seep deposits in the Nakagawa area, Hokkaido, Japan, Acta Palaeontologica Polonica 54 (3), pp. 463-490 : 467

publication ID	https://doi.org/ 10.4202/app.2009.0042
persistent identifier	https://treatment.plazi.org/id/03FBF625-FFD7-213B-7D7B-97CFFA9E2501
treatment provided by	Felipe
scientific name	Bathyacmaea cf. subnipponica Sasaki, Okutani, and Fujikura, 2003
status

Treatment

Bathyacmaea cf. subnipponica Sasaki, Okutani, and Fujikura, 2003 View in CoL

Fig. 2 View Fig .

2003 Bathyacmaea cf. nipponica Okutani, Tsuchida, and Fujikura, 1992 View in CoL ; Hikida et al. 2003: 338, fig. 10: 3.

2007 Bathyacmaea cf. subnipponica Sasaki, Okutani, and Fujikura, 2003 View in CoL ; Jenkins et al. 2007a: 371, fig. 2B, C.

Material.— Eight specimens from the Omagari site: six specimens at UMUT and two at NMM including specimen NMM−228 illustrated in Hikida et al. (2003). One specimen from Yasukawa ( UMUT MM29353) was already illustrated by Jenkins et al. (2007a: fig. 2C). The specimen illustrated by Jenkins et al. (2007a) on fig. 2B was mislabeled as collected at the Yasukawa site, actually the specimen UMUT MM29352 came from the Omagari site ( Fig. 2B View Fig herein).

Dimensions.—The largest specimen ( NMM− 228) is 5.9 mm long, 4.5 mm high, and 2.8 mm high.

Description.—The shell is patelliform, oval in outline. The shell width is about 76% and height is about 50% of its length respectively. The shell surface is ornamented by regularly spaced concentric annulations and irregular radial riblets. The apex is relatively high, corroded, and situated slightly anteriorly of the center at 47% of the shell length. The microstructure is obliterated by diagenesis in the examined specimens, however, shell seems to be composed of at least three layers ( Fig. 2D View Fig 3 View Fig ).

Discussion.—The shells under consideration are most similar to the Recent B. subnipponica from the Nankai Trough, off Japan ( Sasaki et al. 2003) in having a relatively high shell, oval outline, irregular radial riblets, and sturdy concentric ornamentation. Taking into account the large temporal distance and the imperfect preservation of the Cretaceous specimens we leave the latter in open nomenclature.