Ilanga boreia, 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 : 253-255

Ilanga boreia n. sp.

( Figs 28 A–M, Table 19, Key 2: 17)

DNA ref: Ilanga 9 ( Williams et al. 2013; Sumner-Rooney et al. 2016)

COI sequence data: GenBank Accession numbers: HF586278 , HF586279 , HF586280 , HF586281 , HE800626 , HF586282

Type material. Holotype (5.7×11.0 mm) MNHN (IM-2007-18326) . Paratypes: 4 MNHN (MNHN IM-2007-18327, MNHN IM-2007-18328, MNHN IM-2007-18314, IM-2007-18315) and 1 paratype NHMUK 20190459 (as listed below) .

Type locality. North-western New Caledonia, Lansdowne. EBISCO, stn DW2618, 20°06’S, 160°23’E, 280– 304 m.

Material examined. North-western New Caledonia, Bellona. EBISCO: stn DW2559, 20°28’S, 158°41’E, 255– 280 m, 1 dd.—Stn CP2563, 20°28’S, 158°41’E, 235–280 m, 1 dd.—Stn DW2570, 20°27’S, 158°45’E, 235–263 m, 2dd, 2 juv sub.—Stn CP2571, 20°25’S, 158°45’E, 298–309 m, 11 lv (with paratypes MNHN IM-2007-18314, IM-2007-18315 and paratype NHMUK 20190459).—Stn CP2572, 20°23’S, 158°45’E, 324–330 m, 6 lv.—Stn DW2574, 20°20’S, 158°45’E, 358–374 m, 1 dd sub.— New Caledonia, Lansdowne Bank. EBISCO: stn DW2564, 20°25’S, 158°41’E, 333–386 m, 2 dd.—Stn DW2618, 20°06’S, 160°23’E, 280–304 m, 20 lv (with holotype MNHN IM-2007-18326, paratypes MNHN IM-2007-18327 and MNHN IM-2007-18328), 4 dd sub, 1 dd juv.—Stn DW2617, 20°06’S, 160°22’E, 427–505 m, 2 dd.—Stn DW2622, 20°04’S, 160°21’E, 291–323 m, 8 lv, 6 dd sub, 1 dd juv.—Stn DW2639, 20°47’S, 160°01’E, 289–294 m, 2 dd, 2 dd sub, 2 juv sub.— New Caledonia, Chesterfield. EBISCO: stn DW2588, 19°46’S, 158°26’E, 175–200 m, 3 dd juv.—Stn DW2608, 19°33’S, 158°40’E, 393–396 m, 2 dd.— New Caledonia, Grand Passage. BATHUS 4: stn CP905, 19°02’S, 163°16’E, 294–296 m, 1 dd.—Northern New Caledonia, Pétrie Reef. EXBODI: stn DW3924, 18°35’S, 164°23’E, 730 m, 1 dd.—Stn DW3926, 18°35’S, 164°20’E, 364–473 m, 3 dd, 3 dd sub, 2 juv sub.—Stn CP3927, 18°36’S, 164°20’E, 381 m, 4 dd.—Northern New Caledonia. BATHUS 4: stn DW895, 20°15’S, 163°52’E, 315–360 m, 1 dd.—Southern New Caledonia. BATHUS 3: stn DW827, 23°22’S, 168°01’E, 381–469 m, 1 dd.—South-eastern New Caledonia. VAUBAN: stn DR02, 22°18’S, 167°15’E, 425–430 m, 2 dd.—BATHUS 2: stn DW724, 22°48’S, 167°26’E, 344–358 m, 2 dd sub, 5 juv sub.—Loyalty Ridge. MUSORSTOM 6: stn DW485, 21°24’S, 167°59’E, 300–400 m, 1 dd sub.—EXBODI: stn CP3789, 22°11’S, 167°07’E, 335–350 m, 1 juv sub.—Stn DW3846, 22°04’S, 168°38’E, 396 m, 4 dd.

Distribution. New Caledonia area, 200–730 m, lv at 304– 324 m.

Diagnosis. A tall, almost lenticular Ilanga species with a depressed spire, convex whorls and a canaliculate suture, a subangulate periphery, 5 spiral cords on first whorl, no subsutural pleats, very broad angulate umbilicus with a spiral cord at rim, with about 20 axial pleats around umbilicus, up to 8–10 smooth thin spiral cords inside.

Description. Shell: Rather tall for genus (H up to 6.4 mm, W up to 12.3 mm), much wider than high, lenticular, conical to slightly coeloconoidal, glossy; spire depressed, height 0.49×to 0.56×width, about 1.35×to 1.94×aperture height; periphery subangulate; umbilicus very broad and deep. Protoconch ca. 380 μm wide, 1.25 whorls, rounded, with 3 thin, evenly spaced spiral cords and with a straight, slightly expanded terminal lip. Teleoconch up to 4.8 convex whorls with a weak subsutural ramp on first whorls but vanishing on last whorls; early teleoconch whorls with 4–5 smooth spiral cords, quickly vanishing; last whorls smooth with poorly visible spiral threads near periphery. Suture canaliculate. First teleoconch whorl convex, with 5 smooth spiral cords, P2-3-4-5 appearing immediately after protoconch, P1 appearing at half whorl; P2 strongest, situated at edge of subangulate subsutural ramp; thin axial threads between cords; P3, P4 and P5 vanishing at end of the whorl. On second whorl, P1 and P2 vanishing at begin of whorl; subsutural ramp weakening, suture strongly canaliculate; axial threads no longer visible, no subsutural pleats; surface nearly smooth with faint growth lines. On third whorl, narrow translucent subsutural spiral band appearing. Last whorls smooth, except of some faint, barely visible, spiral cords on periphery. Aperture rounded triangular; peristome incomplete; outer and inner lip thin; inner lip thicker against umbilical rim. Base moderately convex, smooth on outer part, with about 20 axial pleats around umbilicus on inner part, some pleats occasionally vanishing near end of whorl; thin, weak spiral cord bordering umbilical rim. Umbilicus broad (diameter 25–35% of shell width), central, with perspective to apex, with angulate rim, with vertical to slightly concave wall, up to 8–10 smooth thin spiral cords inside, gathered in adapical part when less numerous, without axial threads; axial pleats visible in perspective on adapical whorls.

Colour: Teleoconch nacreous white, with 3 bands; adapical and abapical bands with more or less regular, sometimes poorly marked, brownish orange patches; median band with thinner patches or nearly uniformly white; base with weak brownish patches on external half.

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

Remarks. As highlighted by the DNA study, I. boreia n. sp. is sister to I. mesembrine , but the latter has an almost conical (not coeloconoidal) shell shape, less convex whorls with an impressed (not strongly canaliculate) suture and axial pleats around the umbilicus (instead of pleats mainly on adapical whorls inside the umbilicus),

Etymology. From the North (Ancient Greek: βόρειος, α, ον)—after the location of the type locality in northwestern New Caledonia

Figures

FIGURE 28. Ilanga boreia n. sp., New Caledonia. A–F. Holotype MNHN IM-2007-18326, Lansdowne Bank, EBISCO, stn DW2618, 280–304 m, 5.7×11.0 mm. A–C. Shell, apertural, apical and basal views. D. Details of protoconch and first whorl. Scale 100 µm. E. Sculpture on whorls. Scale 1 mm. F. Details of umbilical area. Scale 1 mm. G–I. Paratype MNHN IM-2007- 18315, North-western New Caledonia, Bellona, EBISCO, stn CP2571, 298–309 m, 6.0×10.7 mm. J–L. Lansdowne Bank, EBISCO, stn DW2618, 280–304 m, 5.6×10.9. Scale 5 mm.