Hubertschenckia ezoensis ( Yokoyama, 1890 )

Kiel, Steffen, Amano, Kazutaka & Goedert, James L., 2023, New taxa, records, and data for vesicomyid bivalves from Cenozoic strata of the North Pacific region, Acta Palaeontologica Polonica 68 (2), pp. 297-320 : 315-316

Hubertschenckia ezoensis ( Yokoyama, 1890)

Fig. 13 .

1890 Tapes ezoënsis sp. nov.; Yokoyama 1890: 197, pl. 25: 6–8.

non 1928 Meretrix (Macrocallista) ezoensis (Yokoyama) . Yokoyama 1928: 77, pl. 8: 1.

1951 Tapes (new gen.?) ezoensis Yokoyama ; Minato and Uozumi 1951: 150, pl. 13: 108a–c.

1953 Hubertschenckia ezoensis (Yokoyama) ; Takeda 1953: 85, pl.13: 5.

1960 Hubertschenckia ezoensis (Yokoyama) ; Oyama et al. 1960: 188– 189, pl. 58: 2a–d.

non 1989 Hubertschenckia ezoensis (Yokoyama) ; Honda 1989: 79: 13, 14.

2007 Hubertschenckia ezoensis (Yokoyama) ; Amano and Kiel 2007: 275–277, figs. 6–12.

2007 Hubertschenckia ezoensis (Yokoyama) ; Amano and Jenkins 2007: fig. 2B.

2013 Hubertschenckia ezoensis (Yokoyama) ; Amano et al. 2013: figs. 6K–M.

2016 Hubertschenckia ezoensis (Yokoyama) ; Nobuhara et al. 2016: figs. 2–16.

2016 Hubertschenckia ezoensis (Yokoyama) ; Kiel et al. 2016: fig. 1G.

2022 Hubertschenckia ezoensis (Yokoyama) ; Amano et al. 2022: figs. 10.9a, k.

Material.— Five large specimens ( NRM Mo 204821–25) from the upper Eocene Poronai Formation in Hokkaido, Japan .

Dimensions.—See Table 9.

Remarks.—We illustrate several very large specimens of Hubertschenckia ezoensis to further document the characteristics of this species and their variability. The largest previously published specimen measured 74.6 mm in length Amano and Kiel 2007); the largest specimen reported here exceeds 90 mm in length. One of our specimens has a height of 65 mm. Considering the L/H ratio of ca. 1.8 known from other specimens of Hubertschenckia ezoensis , this specimen could have been almost 120 mm in length, making it the largest Eocene vesicomyid known to date.

Stratigraphic and geographic range.—Upper Eocene to lower Oligocene, Hokkaido, Japan.

Figures

Fig. 13. The vesicomyid bivalve Hubertschenckia ezoensis (Yokoyama, 1890), from the upper Eocene Poronai Formation in Hokkaido, Japan. A. NRM Mo 204823, very large RV; external sculpture (A1) and hinge (A2) views. B. NRM Mo 204821, small articulated specimen; showing ligament (B1) and external ornament and posterior ridge (B2). C. NRM Mo 204824, internal mold of large RV, showing anterior adductor muscle scar; view on right valve (C1) and close-up on hinge area (C2). D. NRM Mo 204825, large articulated specimen, mostly an internal mold; view on right valve (D1) and left valve (D2). E. NRM Mo 204822, hinge of LV.