Ammonicera benhami 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 : 474-475

Ammonicera benhami Squires & Goedert, 1996

Figure 3A–E

Ammonicera benhami Squires & Goedert, 1996, p. 235 , figs. 27–32.

Examined material. MIMB 41136 (lot of 3 specimens), and one specimen , SBMNH 467057 , all from the type locality. One additional specimen , SBMNH 467058 , from LACMIP loc. 16940 [Crescent/McIntosh Formation transition zone of Squires & Goedert (1995)] is herein tentatively identified as A. benhami .

Type material. Holotype: LACMIP 11368 ; Paratypes: LACMIP 11369–11371 .

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

Emended diagnosis. Ammonicera with protoconch sculptured by two spiral cords (prominent central and low outer) separated by a spiral groove; teleoconch with one wide subperipheral groove and low subperipheral cord on both apical and basal surfaces, and prominent nodelike axial ribs.

Remarks. The size range of A. benhami is 0.4 to 0.59 mm in diameter (Squires & Goedert 1996); specimen MIMB 41136–1 ( Fig. 3A ) has a diameter of 0.50 mm. Ammonicera benhami is only known from three localities, two in the Black Hills southwest of Olympia, Washington, and now tentatively from a single locality (weathered and no longer accessible) in the Doty Hills, Lewis County, Washington. The two localities in the Black Hills represent deposition between basalt boulders within the tidal zone ( Squires & Goedert 1994, 1996) whereas the Doty Hills localities may represent shallow water taxa transported a short distance into deeper waters off volcanic islands ( Squires & Goedert 1995).

Figures

FIGURE 3. Ammonicera benhami (SEM), specimen MIMB 41136–1, apical view (A, C) and apical view at oblique angle (B, E); specimen MIMB 41136–2, umbilical view (D); general view (A, B); detail of the protoconch (C-E). Scale bars: A, B—100 μm; C-D—20 μm.