Orbitestella palaiopacifica Squires & Goedert, 1996

Chernyshev, Alexei V. & Goedert, James L., 2021, New species of latest Eocene / earliest Oligocene microgastropods (Heterobranchia Orbitestellidae and Omalogyridae) from the Gries Ranch Formation, Lewis County, Washington State, USA, Zootaxa 4981 (3), pp. 469-480 : 471

Orbitestella palaiopacifica Squires & Goedert, 1996

Figure 1A–C

Orbitestella palaiopacifica Squires & Goedert, 1996, p. 233 , figs. 22–26.

Examined material. MIMB 41133 (lot of 6 specimens) , SBMNH 467055 (lot of 2 specimens), from the type locality .

Type material. Holotype: LACMIP 11365 ; Paratypes, LACMIP 11366–11367 .

Type locality. LACMIP loc. 16655, Larch Mountain , Black Hills , Washington State, USA; Crescent Formation, middle early Eocene .

Diagnosis. “An Orbitestella with an upper whorl surface crossed by narrow axial ribs, a keel-like carina on the shoulder, axial ribs in the interspace between the carina on the basal margin and the carina on the edge of the umbilicus, and a wide but deep umbilicus showing overlapping whorls in its interior.” (Squires & Goedert 1996).

Remarks. Shells of O. palaiopacifica were reported to be up to 0.3 mm high with a diameter of 0.53 mm by Squires & Goedert (1996); a new specimen (MIMB 41133–2; Fig. 1B ) is now the largest known specimen with a diameter of 0.9 mm. New specimens of O. palaiopacifica show that the axial ribs cross the prominent keel-like carina on the shoulder, and spiral threads are present on most surfaces, including the apical and basal carinae. Squires & Goedert (1996) stated that the protoconch of O. palaiopacifica was apparently smooth, but we think this is due to poor preservation of the protoconch. The protoconch surface of the newly available specimens appears also to be corroded. Orbitestella palaiopacifica is still known only from two localities of the Crescent Formation in the Black Hills southwest of Olympia, Washington.

Figures

FIGURE 1. Orbitestella palaiopacifica Squires & Goedert (SEM). A, specimen MIMB 41133–1, apical view; B, specimen MIMB 41133–2, umbilical view; C, specimen MIMB 41133–3, apertural view. Scales: 100 µm.