Ilanga corrineae, Vilvens & Williams, 2020

Vilvens, Claude & Williams, Suzanne T., 2020, New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific, Zootaxa 4732 (2), pp. 201-257 : 240-242

Ilanga corrineae n. sp.

( Figs 21 A–I, Table 12, Key 2: 4)

DNA ref: Ilanga 21 ( Sumner-Rooney et al. 2016)

COI sequence data: GenBank Accession numbers: MK393382 –84.

Type material. Holotype (5.5× 8.7 mm) MNHN IM-2013-58754 . Paratype MNHN IM-2013-58753 as listed below .

Type locality. Papua New Guinea, New Ireland, KAVIENG 2014, stn DW4473, 02°43’S, 150°36’E, 93–149 m.

Material examined. Papua New Guinea, New Ireland. KAVIENG 2014: stn DW4473, 02°43’S, 150°36’E, 93–149 m, 2 lv (holotype and paratype) . — Western Australia. Southern Surveyor: stn SS1005/133, off Red Bluff , 4°1.03’S, 113°2.03’E, 100–101 m, 2 lv ( WAM S84074 , DNA sequenced for one specimen) . — Stn SS 1005/141, off Ningaloo South, 22°4’35.04’’S, 113°48’48.6’’E, 101–102 m, 3 lv ( WAM S25793 , DNA sequenced for three specimens)

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Distribution. Papua New Guinea, lv at 93-129 m, and north Western Australia, lv at 100– 102 m.

Diagnosis. A rather small Ilanga species with a moderately depressed, conical to slightly cyrtoconoidal spire, a weakly subangulate periphery with some faint peripheral spiral cords, four spiral cords on first teleoconch whorl and one possible additional cord on second one, subsutural pleats on median whorls, a very convex last whorl, broad subangulate umbilicus with 35–40 axial pleats around (but poorly marked on the last half near the aperture), bordered by an internal thin spiral cord and with about seven spiral cords inside.

Description. Shell: Rather small in size for genus (H up to 6.0 mm, W to 10.4 mm), wider than high, shape conical to slightly cyrtoconoidal, glossy; spire moderately depressed, height 0.58–0.63×width, about 1.67×to 1.82×aperture height; weakly subangulate periphery; umbilicus broad and deep. Protoconch ca. 250–280 μm wide, 1.25 whorls, rounded, with a straight terminal lip. Teleoconch up to 4.6 slightly convex whorls; early whorls with 4–5 smooth spiral cords; intermediate whorls with strong subsutural axial pleats; last whorls smooth with some faint spiral cords on periphery. Suture canaliculated on first whorls, impressed on last ones. First teleoconch whorl convex, with 4 smooth spiral cords Pi appearing immediately except P1 usually appearing after half teleoconch whorl; P2 the strongest; subsutural ramp forming at end of whorl, with P2 on rim; distance between cords about 1.5×to 2×width of cords. On second whorl, all cords widening and flattening; S2 appearing in some specimens; low axial pleats appearing at half of second teleoconch whorl, covering adapical third of whorl. On third whorl, subsutural pleats stronger especially in area close to suture; subsutural ramp and adapical spiral cords vanishing, P3 and P4 (and S2 if present) flattened. On last whorls, axial pleats weakening and vanishing; abapical cords completely flat, with a thin groove between them. Aperture subcircular; peristome incomplete; outer and inner lip thin; inner lip with a weak thickening against umbilical rim. Base moderately convex; outer part smooth, inner third with 35–40 axial pleats around umbilicus, especially poorly marked on last half whorl near aperture. Umbilicus broad (diameter about 29% of shell width), central, with perspective to apex, with subangulate rim, bordered by an internal smooth spiral cord, with about seven spiral cords inside, possible weak axial threads near aperture rim.

Colour: Teleoconch nacreous white with two bands (one peripheral and one subsutural) of brownish chevronshaped brownish flames; base paler, with possible brownish patches.

Operculum: Corneous, multispiral with central nucleus, light brown, translucent.

Remarks. Ilanga corrineae n. sp. is rather close to I. cosmia from Tonga Islands, but this slightly larger species (H up to 6.5 mm, W to 10.7 mm) has a more strictly conical shape with nearly flat whorls, and a more subangulate and only weakly convex last whorl.

Regarding the east-northern Papua New Guinea area, the new species may be compared to I. eurystoma , but this species has 6 spiral cords on the first teleoconch whorl, much thinner subsutural axial pleats, an umbilicus with an angulate rim and axial threads inside the umbilicus.

Etymology. After the first name of the second author’s favourite (and only) sister, Corrine Michelle Stewart.

Figures

FIGURE 21. Ilanga corrineae n. sp., Papua New Guinea, New Ireland, KAVIENG 2014, stn DW4473, 93–149 m. A–F. Holotype MNHN IM-2013-58754, 5.5×8.7 mm. G–I. WAM S84074, Australia, Off Red Bluff, Western Australia, 24°1.03’S, 113°2.03’E, 100-101 m, Southern Surveyor. Scale 5 mm.