Pleurophopsis chinookensis ( Squires and Goedert, 1991 )

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 : 310-311

Pleurophopsis chinookensis ( Squires and Goedert, 1991)

Fig. 10 .

1990 Calyptogena n. sp.; Goedert and Squires 1990: fig. 20p, o. 1991 Calyptogena chinookensis Squires and Goedert, 1991: 414 , figs.

2.7–2.11. non 1993 Calyptogena chinookensis Squires and Goedert ; Goedert and

Squires 1993: 53, figs. 3–5. non 1995 Calyptogena (Calyptogena) chinookensis Squires and Goedert ; Goedert and Campbell 1995: 24, table 1. 2007 Adulomya chinookensis ( Squires and Goedert, 1991) ; Amano and

Kiel, 2007: 279, figs. 19–23.

Material.— 15 specimens ( NRM Mo 204815–20) from the upper Eocene Bear River seep deposit, Washington State, USA .

Dimensions.—See Table 7.

Remarks.—To supplement previous documentations and descriptions of this species ( Squires and Goedert 1991; Amano and Kiel 2007), here we illustrate (i) features of the shell surface ( Fig. 10A ) including the absence of a lunular incision ( Fig. 10E 1 , E 2 ); (ii) a fully articulated specimen in dorsal view to show its true inflation ( Fig. 10C ); (iii) the short ligament ( Fig. 10A 2 ); (iv) the small, elongate anterior pedal retractor scar that is distinct from the adductor muscle scar ( Fig. 10C ); and (v) the hinge of a right valve showing two strong, radiating cardinal teeth, namely cardinals 1 and 3b, and a large and deep subumbonal pit ( Fig. 10E 3 ). This species was originally reported from middle to upper Eocene strata. Oligocene specimens previously assigned to P. chinookensis differ from those from the upper Eocene type locality by being notably smaller, less inflated, having a different arrangement of the hinge teeth, and possessing a lunular incision. These specimens belong to either Squiresica knapptonensis ( Amano and Kiel, 2007) or S. plana sp. nov., as discussed above.

Stratigraphic and geographic range.—Humptulips Formation and Bear River seep deposit, Middle to upper Eocene, southwestern Washington State, USA.

Figures

Fig. 10. The vesicomyid bivalve Pleurophopsis chinookensis (Squires and Goedert, 1991), from the upper Eocene Bear River seep deposit in western Washington State, USA. A. NRM Mo 204815, semi-articulated specimen with preserved shell material; view on LV (A1); dorsal view showing short ligament (A2). B. NRM Mo 204816, largely an internal mold, view on LV showing anterior adductor muscle scar. C. NRM Mo 204817, closely articulated specimen in dorsal view, showing true width. D. NRM Mo 204818, view on RV of internal mold showing internal posterior ridge. E. NRM Mo 204819, anterior part of RV with preserved shell, showing lack of lunular incision (E1, E2) and hinge dentition (E3). Abbreviations: aprs, anterior pedal retractor scar; sub. pit., subumbonal pit.

Fig.1. Mapshowing localitiesin western WashingtonState,USA.1, coastal sites between Rasmussen Creek and Jansen Creek (Makah Formation); 2, Whiskey Creek site (Pysht Formation); 3–5, sites LACMIP loc. 12385, CSUN loc. 1583, “East Fork Bridge site” (Humptulips Formation); 6, UWBM loc. B7452 in the Canyon River (Lincoln Creek Formation); 7, SR2 and SR4, Satsop River (Lincoln Creek Formation); 8, Bear River seep deposit; 9, West Fork of Grays River (Siltstone of Unit B); 10, Frankfort (Astoria Formation); 11, sites around Rocky Point (Astoria Formation).

Fig. 2. The small vesicomyid bivalves Vesicomya? sp. 1 and sp. 2, from Oligocene seep deposits in the Lincoln Creek Formation, western Washington State, USA. A. Vesicomya? sp. 1 from the early Oligocene SR2 site, Satsop River. NRM Mo 204811, left side view (A1) and dorsal view on LV and dorsal side of actual specimen (A2); A3, A4, X-ray section through the hinge area, with our interpretations; A5–A7, 3D renderings of the specimen. B, C. Vesicomya? sp. 2 from the late Oligocene SR4 site, Satsop River. B. NRM Mo 204701, disarticulated specimen, view on RV with naticid drill hole on the umbo (B1) and on the LV showing the truncate posterior margin (B2). C. NRM Mo 204702, RV in anterior view, showing inflation and lunular incision (C1) and dorsal view, showing lunular incision (C2).

Fig. 3. The vesicomyid bivalve Isorropodon humptulipsense sp. nov., from middle to upper Eocene strata in western Washington State, USA. A. Rubber cast of the paratype, NRM Mo 204722, Humptulips Formation, CSUN loc. 1583, hinge area, RV (A1), LV (A2). B. Holotype, NRM Mo 204723, Humptulips Formation, CSUN loc. 1583, internal mold, view on LV.C. NRM Mo 204724, Humptulips Formation, LACMIP loc. 12385, articulated specimen, view on anterodorsal margin showing lunular incision. D. Paratype, NRM Mo 204733, Humptulips Formation, near East Fork Bridge site, view on anterodorsal margin and anterior adductor muscle scars. E. Paratype, NRM Mo 204744, Siltstone Unit B along Grays River, specimen with partially preserved shell. F. Paratype, NRM Mo 204743, Siltstone Unit B along Grays River, internal mold showing pallial line with slight indentation on RV. G. Internal mold, USNM 534952, Humptulips Formation, CSUN loc. 1583, view on RV with pallial line curving evenly into posterior adductor muscle scar (re-illustrated from Amano and Kiel 2007).