Ilanga lauensis Vilvens & Williams 2020, n. sp.
Creators: name: Vilvens, Claude
name: Williams, Suzanne T.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Trochida
Solariellidae
Ilanga
Ilanga lauensis

description: Ilanga lauensis n. sp.
(Figs 26 A–L, Table 17, Key 2: 16)
Type material. Holotype (5.8× 10.2 mm) MNHN IM-2000-34411. Paratypes: 4 MNHN IM-2000-34412, MNHN IM-2000-34413 and 1 paratype NHMUK 20190465 (as listed below).
Type locality. Fiji, Lau Ridge, Vanua Balavu Is., BORDAU 1, stn DW1440, 17°11’S, 178°43’W, 259–348 m.
Material examined. Fiji. MUSORSTOM 10: stn DW1374, 18°19’S, 178°06’E, 259–348 m, 2 dd. —BORDAU 1: stn DW1440, 17°11’S, 178°43’W, 190–308 m, 2 lv, 3 juv lv (with holotype IM-2000-34411 and paratype 1 MNHN IM-2000-34412. — Stn DW 1464, 18°09’S, 178°38’W, 285–300 m, 3 lv, 1 dd sub, 9 dd juv. — Stn DW 1465, 18°09’S, 178°39’W, 290–300 m, 2 dd. — Stn DW 1494, 18°55’S, 178°29’W, 240–319 m, 5 lv, 2 dd sub. — Stn DW 1497, 18°44’S, 178°25’W, 335–350 m, 9 lv. — Stn DW 1506, 18°09’S, 178°37’W, 294–300 m, 2 dd, 1 dd sub, 1 dd juv. — Stn DW 1507, 18°09’S, 178°38’W, 255–290 m, 11 lv, 4 dd sub (with 3 paratypes MNHN IM-2000-34413 and paratype NHMUK 20190465).
Distribution. Fiji, 290–335 m (lv).
Diagnosis. Medium-sized Ilanga species with moderately depressed, conical spire, subangulate periphery, 4 spiral cords on first teleoconch whorl and 5 or 6 on second one, no or very weak subsutural pleats, broad subangulate umbilicus with a weak spiral cord at rim, without axial pleats around rim and 10–12 smooth thin spiral cords on umbilical shell walls.
Description. Shell: Medium size for genus (H up to 6.0 mm, W up to 10.3 mm), wider than high, conical, glossy; spire moderately depressed, height 0.52×to 0.58×width, 1.53×to 2.16×aperture height; periphery weakly subangulate; umbilicus broad and deep. Protoconch ca. 200–250 μm wide, 1.25 whorls, rounded, with a straight terminal lip. Teleoconch up to 4.6 convex whorls with a weak subsutural ramp on second whorl but absent on other whorls; no or very weak subsutural pleats; early teleoconch whorls with 4 and later 5–6 smooth spiral cords, vanishing on next whorls; last whorls smooth with hardly visible spiral threads near periphery. Suture weakly canaliculated on second whorl, impressed on other whorls. First teleoconch whorl convex, sculptured with 4 smooth spiral cords appearing immediately after protoconch; P1 and P2 slightly stronger than other cords; no subsutural ramp. On sec- ond whorl, S2 and/or S3 appearing; weak subsutural ramp with P1 at rim. On third whorl, spiral cords flattening and weakening, subsutural ramp disappearing; very weak subsutural pleats occasionally forming; narrow translucent subsutural spiral band. Last whorls nearly smooth, some faint spiral cords around periphery. Aperture rounded triangular; peristome incomplete; outer and inner lip thin; inner lip without obvious thickening against umbilical rim. Base convex, smooth, without axial pleats around umbilicus and with a thin, weak spiral cord bordering umbilical rim. Umbilicus broad (diameter 20–25% of shell width), central, with perspective to apex, with subangulate rim; slightly convex umbilical wall with 10–12 smooth, thin spiral cords, without clearly visible axial threads; umbilical shell walls of adapical whorls occasionally with weak axial pleats.
Colour: Teleoconch nacreous white with 3 bands patterned with brown, brownish orange or pinkish brown chevrons, median band narrower; base paler with an external band of regular brownish patches.
Operculum: Corneous, multispiral with central nucleus, light brown.
Remarks. See under Ilanga helicoides description.
Etymology. After the type locality, Vanua Balavu Island, belonging to Lau Archipelago (Fiji).
description: Published as part of Vilvens, Claude & Williams, Suzanne T., 2020, New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific, pp. 201-257 in Zootaxa 4732 (2) on pages 249-251, DOI: 10.11646/zootaxa.4732.2.1, http://zenodo.org/record/3663329