Ilanga dongshaensis, 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 : 244

Ilanga dongshaensis n. sp.

( Figs 23 A–I, Table 14, Key 2: 5)

COI sequence data: GenBank Accession numbers: MK393375 –79.

Type material. Holotype (6.5× 10.7 mm) MNHN IM-2013-50119 . Paratypes: 4 MNHN MNHN IM-2013-50118 , MNHN IM-2013-59760, IM-2013-59456 & IM-2013-59450.

Type locality. South China Sea, DONGSHA 2014, stn CP4124, 21°02’N, 116°29’E, 307–309 m.

Material examined. South China Sea. DONGSHA 2014: stn CP4124, 21°02’N, 116°29’E, 307–309 m, 2 lv (holotype MNHN IM-2013-50119, paratype MNHN IM-2013-50118) . —ZHONGSHA 2015: stn DW4158, 21°05’N, 116°44’E, 310–325 m, 3 lv (paratypes MNHN IM-2013-59760, IM-2013-59456, IM-2013-59450)

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Distribution. South China Sea, lv at 309– 310 m.

Diagnosis. A medium-sized Ilanga species with a moderately elevated, conical spire, a rounded to weakly subangulate periphery with some faint spiral cords, five spiral cords on first teleoconch whorl, subsutural pleats on median whorls, slightly subangulate umbilicus with axial pleats around, bordered by an internal smooth spiral cord and with axial threads and eight spiral cords inside.

Description. Shell: Medium in size for genus (H up to 6.6 mm, W to 10.3 mm), wider than high, shape conical, glossy; spire moderately elevated, height 0.64–0.76×width, about 1.91×to 2.33×aperture height; rounded to weakly subangulate periphery; umbilicus rather broad and deep. Protoconch ca. 250–300 μm wide, 1.25 whorls, rounded, with a weak straight terminal lip. Teleoconch up to 4.5 convex whorls; early whorls with five smooth spiral cords; intermediate whorls with 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 five smooth spiral cords, Pi appearing immediately, similar in size; subsutural ramp with P1 near P2 on rim; distance between cords about 1.5×to 2×width of cords. On second whorl, all cords widening; short axial pleats appearing after half of first teleoconch whorl, covering adapical quarter of whorl. On third whorl, pleats becoming subsutural; subsutural ramp and all spiral cords vanishing. On fourth whorl, axial pleats weakening and vanishing. Last whorl completely smooth, except 6 very faint spiral cords on periphery of whorl. Aperture subtriangular; 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 about 30 strong axial pleats around umbilicus, closer and thinner near aperture. Umbilicus broad (diameter 18–26% of shell width), central, with perspective to apex, with subangulate rim, bordered by granular spiral cord; whorl face inside umbilicus with 8 spiral cords and rather strong axial threads forming weak reticulate pattern.

Colour: Teleoconch nacreous white with brownish orange with broad brownish axial flames; base pinkish white.

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

Remarks. Regarding the strong axial threads inside the umbilicus, I. dongshaensis may be compared to I. comes from the Philippines, but I. comes is slightly larger (H up to 6.8 mm, W up to 11.3 mm), has a more depressed spire (height 0.52–0.62×width, instead of height 0.64–0.76×width here), only 4 spiral cords on the early whorls (instead of 5), a slightly broader umbilicus and a greyish white colour with brownish flames or patches.

Etymology. After Dongsha Islands, for which the expedition that collected type material was named.

Figures

FIGURE 23. Ilanga dongshaensis n. sp., South China Sea, DONGSHA 2014, stn CP4124, 309–307 m. A–D. Holotype MNHN IM-2013-50119, 6.6×10.3 mm. E–I. Paratype MNHN IM-2013-50118, 6.1×9.4 mm. Scale 5 mm.