Ilanga gotoi ( Poppe, Tagaro & Dekker, 2006 )

Vilvens, Claude & Williams, Suzanne T., 2020, New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific, Zootaxa 4732 (2), pp. 201-257 : 220-222

Ilanga gotoi ( Poppe, Tagaro & Dekker, 2006)

( Figs 10 A–H, Key 2: 10)

COI sequence data: GenBank Accession number: HF586277

Microgaza gotoi Poppe, Tagaro & Dekker, 2006: 130–131 , pl. 69, figs 4–5. Type locality: Philippines, Aliguay Island, 50– 200 m.

Microgaza gotoi Vilvens 2009: 87 , figs 57–61.

Ilanga gotoi — Williams et al. 2013: 895 .

Type material. Holotype NMP uncatalogued, labelled “ Ex. Coll. Conchology, Inc. nr. 217175” ( Poppe et al. 2006).

Material examined. Philippines. PANGLAO 2004: stn T31, 9°33’N, 123°42’E, 100–140 m ( MNHN IM- 2007-18349 DNA sample, MNHN 6 lv, 2 sub lv).— Aliguay Is., off North of Mindanao , 150–300 m, 1 lv (C. Vilvens coll.) .

Distribution. Philippines 50–200 m ( Poppe et al., 2006); Eastern Indonesia, 181–184 m (dd) ( Vilvens 2009).

Diagnosis. A large sized Ilanga species with a depressed, conical spire, an angular periphery, 4 spiral cords on first teleoconch whorl, no subsutural pleats, angulate umbilicus with numerous axial threads all around, bordered by a smooth spiral cord at rim and 18–20 spiral cords inside.

Description (supplementary—based on the original description and DNA sample studied). Shell: Large size for genus (H up to 8.5 mm, W up to 18.4 mm), lenticular, much wider than high, shape conical with very large apical angle, glossy, fragile; spire strongly depressed, height 0.44×to 0.47×width; angular periphery; umbilicus very broad and deep. Protoconch ca. 270–300 μm wide, 1.25 whorls, rounded, without spiral cords; straight terminal lip with a thin varix and a very weak terminal expansion. Teleoconch up to 4.8 slightly convex whorls, without shoulder and without subsutural pleats, with spiral cords on first whorls disappearing on next whorls and thin spiral threads on last whorls, mostly visible under suture and on periphery. Suture distinct, canaliculated on first whorls. First teleoconch whorl convex, sculptured by 4 thin, evenly spaced, similar spiral cords appearing immediately; P2 at edge of subangulate subsutural ramp; weak, very thin prosocline threads. On second whorl, P4 disappearing covered by next whorl; low subsutural axial pleats appearing, distance between them about 0.5×width of pleats; P2 and P3 vanishing on second half of second teleoconch whorl; subsutural ramp vanishing. On third teleoconch whorl, axial pleats disappearing and axial threads entirely traversing whorl. On fourth whorl, about 4 thin subsutural and 3 very weak suprasutural spiral threads; narrow translucent subsutural spiral band. On last whorls, adapical and abapical spiral threads more numerous, weak, poorly visible spiral threads in median area; abapical spiral threads around angular periphery; possibly subsutural reticulate pattern made by axial threads crossing spiral threads. Aperture subelliptical; peristome incomplete; outer and inner lip thin, without thickening; outer lip with a median obtuse angle, joining inner lip with a rounded angle. Base convex; outer half smooth, inner half with radial threads and thin spiral grooves on big specimens, making a fine reticulate pattern. Umbilicus broad (diameter about 32–34% of shell width), central, with perspective to apex, with angular rim marked by a smooth spiral cord; wall concave in its abapical part, convex in its adapical part, with 18–20 smooth spiral cords, possibly with weak, poorly visible axial threads; axial pleats on adapical whorls within umbilicus.

Colour: Teleoconch white with light orange brownish pattern, last whorls with brown zig zag lines, making distinct subsutural and peripheral areas with chevron shaped lines; base lighter with large axial patches.

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

Remarks. Poppe et al. (2006) noted this species had been identified in the shell trade as Archiminolia zacalloides ( Schepman, 1908) ( Fig. 11I ), a smaller species from Indonesia which is not as depressed and has a more rounded aperture.

Figures

FIGURE 10. Ilanga gotoi (Poppe, Tagaro & Dekker, 2006), Philippines. A–D. MNHN IM-2007-18349, PANGLAO 2004, stn T31, 100–140 m, 6.4×14.5 mm. E–H. Aliguay Is., off North of Mindanao, 150–300 m, 8.5×18.4 mm (C. Vilvens coll.). Scale 5 mm.

FIGURE 11. A–B. Microgaza fulgens Dall, 1907, from Dall, 1925–Pl.36, Figs.2,10. Width: 10.5–14 mm (dimensions in the description: 6×8–10 mm). C. Ilanga fulgens (as Microgaza fulgens) from Sasaki, 2000, p.77 pl.38–114. Scale 5 mm. D–G. Ilanga fulgens (Dall, 1907), Japan, Wakayama pref., Kushimoto, 90–180 m, 5.8×9.3 mm (C. Vilvens coll.). H. Ilanga fulgens (as Microgaza fulgens) from Natural History Museum of Rotterdam Web site (http://www.nmr-pics.nl/), NMR 42452, Japan, Wakayama Pref, Nada-Cho, about 8 mm. I. Solariella zacalloides Schepman, 1908, from Schepman, 1908- Pl. III, 6. Dim: 6x10.5 mm.