Crebrivolutopsius labidentatus Mclean & Clark 2023, n. sp.

Crebrivolutopsius labidentatus n. sp.

Figures 19 K–M

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Type locality: Petrel Bank, NE of Semisopochnoi Island, Rat Ids., Aleutian Is., Alaska (52°27.6 N, 179°49.2 W); 213 m.

Type material: Holotype, CASIZ 137735, 107.6 mm. ♀ (leg. E. Kools, 22 June, 2000); Paratypes: PT 1, CASIZ 236192, 95.0 mm. Type locality; Pt 2, CASIZ 149894, 36.8 mm. S of Adak Island, Andreanof Ids. (51°54.6 N, 176°36.0 W), 264 m (NMFS 94-200001 - 173); Pt 3, SBMNH 464991, 101.3 mm. SSE of Buldir Island (52°07.07 N, 176°15.06 E) (NMFS 143-201401 - 163); Pt 4, LACM 3660, 72.4mm. S of Adak Island, Andreanof Ids. (51°35.21 N, 176°23.02 W), 382 m (NMFS 95-199701 - 152); Pt 5, LACM 3658, 69.1 mm. S of Rat Islands (51°38.2 N, 178°09.4 E), 198 m (NMFS 94-200201 - 129); Pt 6, RNC 4657, 81.2 mm. Petrel Bank, Rat Ids. (52°30.45 N, 179°32.4 W), 141 m (NMFS 94-200201 - 181); Pt 7, RNC 4658, 72.3 mm. S of Amchitka Island, Rat Ids. (51°27.08N, 178°36.14 E), 388 m (NMFS 147-200401 - 174); Pt 8, David P. Berschauer coll. 70.8 mm, SE of Buldir Island (52°03.1 N, 177°23.9 E), 130 m (23-1997-1-198).

Referred material: RNC 4622, 1 sp., 95.4 mm. S of Buldir Island (52°19.26 N, 175°48.64 E), 219 m (NMFS 143-200401 - 163); RNC 4628, 3 sp., 67.9–87.9 mm. S of Kanaga Island (51°46.57 N, 177°28.97 W), 80 m (147- 200401-166); RNC 4629, 1 sp., 117.7 mm. WSW of Buldir Island (51°16.57 N, 175°19.05 E), 168 m (NMFS 94- 200201 - 166); 1 sp., Koen Fraussen, 62.1 mm. WSW of Buldir Island (52°17.31 N, 175°20.83 E), 244 m (NMFS 147-200401 - 194); 1, RNC 4587, 14.18 mm. E of Buldir Island (52°19.77 N, 175°48.56 E).

Description: Shell relatively large, (to 107.5 mm, holotype) profile high, whorls rounded, with moderately impressed suture; uniformly white; periostracum lacking. Protoconch relatively small for this subfamily, 3.7–4.1 mm in diameter, two whorls; teleconch with four whorls; spiral sculpture of raised, angular ridges, with deeply channeled interspaces that are much broader than the ribs, and bearing 1–5 fine spiral lirae above the suture; basal cords with deep bifurcating incisions. Inner lip region sharply delimited, but not producing expansive parietal glaze, mature lip with moderate flare and thickening, base of columella truncate; spiral sculpture producing seven or eight projecting primary prongs or teeth, alternating with similar but smaller teeth between, on the anterior half of outer lip (Fig.19 L); canal short, broad. Operculum large, but not filling aperture; nucleus terminal.

Radula (Fig.19 M). Rachidian tooth broad, crescentic, strongly indented anteriorly, bearing four equal, stout cusps. Lateral teeth with three, well-spaced cusps, outer cusp large, thick, strongly curved; inner cusp only slightly curved, about 2/3 the length of the outer denticle; central cusp about half as long as inner cusp.

Remarks: Crebrivolutopsius labidentatus differs from all other known Volutopsiinae by the 1) spiral sculpture showing a peculiar difference between the upper and lower part of the whorls, 2) the relatively small protoconch when compared to the adult size, 3) the presence of apertural denticles, and 4) the narrow columellar callus. The radula also differs from most Volutopsiinae, with a more curved rachidian tooth and lateral teeth that are clearly tricuspid as in Neptuneinae, this is one of only two known species Volutopsiinae [the other is Pyrulofusus dexius (Dall, 1907), Clark, pers. observ.] with tricuspid lateral teeth. Both species are endemic to the Aleutians. This is the only known species among the northern Buccinidae with denticles on the outer lip. Perhaps this is a modification for feeding on bivalves as in some other groups. A general discussion of labial “serrations” or dentations is given in Vermeji, 2014.

Etymology: Latin, combination of labium “lip” and dentatus “toothed” in reference to the prong-like denticles at the base of the outer lip.

Distribution: Occurs throughout much of the central and western Aleutians, from S of Little Tanaga Island (176°W) to west of Buldir Island (176°20’E) at depths of 80– 383 m.

Habitat: Bedrock, gravel, and cobble sand substrates, with bottom temperatures of 3.7–4.4°C.