Otitoma sororcula, Morassi & Nappo & Bonfitto, 2017

Morassi, Mauro, Nappo, Andrea & Bonfitto, Antonio, 2017, New species of the genus Otitoma Jousseaume, 1898 (Pseudomelatomidae, Conoidea) from the Western Pacific Ocean, European Journal of Taxonomy 304, pp. 1-30 : 7-9

Otitoma sororcula sp. nov.

urn:lsid:zoobank.org:act:112C802A-78C0-47EB-9CF6-50306954AAD4

Fig. 2 A–I

Etymology

The specific epithet comes from the Latin ‘ sororcula ’, meaning ‘a little sister’, alluding to its strong resemblance to Otitoma kwandangensis ( Schepman, 1913) .

Type material

Holotype

FIJI ISLANDS: MUSORSTOM 10 Stn, CP 1323, Bligh Water , 17°16.1 ′ S, 177°45.7 ′ E, 143–173 m ( MNHN IM-2000-32582 ).

Paratypes

FIJI ISLANDS: paratype 1, same data as holotype ( MZB 60210); paratype 2, MUSORSTOM 10, Stn DW1329, Bligh Water, 17°19.3 ′ S, 177°47.4 ′ E, 102–106 m ( MNHN IM- 2000-32583); paratypes 3–4, MUSORSTOM 10, Stn DW1365, SE of Viti Levu, 18°12.7 ′ S, 178°32.4 ′ E, 295–302 m ( MNHN IM- 2000-32584); paratypes 5–6, MUSORSTOM 10, Stn DW1359, SE of Viti Levu, 17°49.7 ′ S, 178°47.8 ′ E, 183–188 m ( MNHN IM- 2000-32585); paratype 7, MUSORSTOM, 10 Stn DW1356, SE of Viti Levu, 17°50.3 ′ S, 178°48.0 ′ E, 203–208 m ( MNHN IM- 2000-32586).

Additional material

FIJI ISLANDS: 2 spms, MUSORSTOM 10, Stn CP1323, Bligh Water, 17°16.1 ′ S, 177°45.7 ′ E, 143– 173 m; 4 spms, MUSORSTOM 10, Stn DW1329, Bligh Water, 17°19.3 ′ S, 177°47.4 ′ E, 102– 106 m.

Description

Shell claviform-fusiform (b/l 0.36–0.44; a/l 0.43–0.50), somewhat pupoid. Teleoconch of 3½–4¾ convex whorls with median periphery. Suture distinct, bordered by a prominent spiral cord, demarcated by a distinctly concave sutural ramp. Axial ribs rather straight, opisthocline and distinctly rounded, broader than intervals between them, developed mainly in peripheral region, becoming much weaker to obsolete and slightly arcuate on sutural ramp. 8–11 axial ribs on penultimate whorl, 11–14 on last whorl. Spiral sculpture of prominent, narrow, widely-spaced spiral cords, becoming conspicuously nodulose where crossing axial ribs ( Fig. 2F). Earlier 1–2 whorls with a subsutural cord and two cords on abapical part of whorl, increasing to 3 and 4 on penultimate and last whorl, respectively. Sutural ramp with 1–2 weak spiral cords on abapical side. Last whorl with 9–12 spiral cords on base and rostrum. Interspaces between spiral cords lacking secondary sculpture ( Fig. 2G). Aperture rather narrow and almost linear, but strongly constricted at entrance to siphonal canal. Siphonal canal short, relatively wide, expanding slightly distally. Inner lip with moderately thick callus with distinct parietal pad. Outer lip edge sharp, preceded by a wide, low, rounded varix. Stromboid notch distinct. Anal sinus rather deep, apically rounded, asymmetrically U-shaped, with strongly constricted opening. Protoconch papilliform, of ¼–1½ whorls ( Fig. 2 H–I), diameter 0.62–0.89 mm. Color white or yellowish-white with an amber-orange band bordering the adapical suture.

Dimensions

Holotype: 6.0 × 2.3 mm, aperture height 2.9 mm. Paratype 1 (largest specimen): 6.6 × 2.4 mm, aperture height 3.0 mm; paratype 7 (smallest specimen): 4.3 × 1.9 mm, aperture height 1.85 mm.

Remarks

Among its described congeners, Otitoma sororcula sp. nov. most closely resembles Otitoma kwandangensis ( Schepman, 1913) ( Fig. 2 J–K). The two species are nearly indistinguishable from each other in teleoconch morphology, but differ in protoconch structure, which in O. sororcula sp. nov. is papilliform, of 1¼–1½ whorls while in Otitoma kwandangensis it “is broken at the tip and the preserved part consists of 2.7 volutions” ( Shuto 1970: 166, plate X, fig. 19). Otitoma sororcula sp. nov. is remarkably smaller than the type specimen of Drillia kwandangensis (4.3–6.6 mm vs 8.2 mm, mean 5.15 mm in length) and differs in color (white or yellowish-white with an amber-orange band bordering the adapical suture and tinged with the same color on the adapical part of the base vs a uniform red-brown). The new species is comparable to Otitoma timorensis ( Schepman, 1913) , in protoconch features and shape, but judging from the photographs of the holotype ZMA 138096 ( Fig. 2 L–N), Otitoma sororcula sp. nov. differs in lacking a secondary spiral sculpture, having a different number of spiral cords (3 instead of 2 on penultimate whorls), which are more distinctly nodulous where crossing the axial ribs, and in having broader and more bulging axial ribs.