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Taxon profile

species

Ilanga gotoi (Poppe, Tagaro & Dekker, 2006)

kingdom Animalia - animals »  phylum Mollusca - mollusks »  class Gastropoda - gastropods »  order Trochida »  family Solariellidae »  genus Ilanga

Scientific synonyms

Microgaza gotoi Poppe, Tagaro & Dekker, 2006

Images

Ilanga gotoi

Author: Poppe, G. et al

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Description

Shell large for the genus. Flattened outline with a sunken spire and about 5 whorls. Protoconch small. The first whorls covered with 3 spiral ribs that disappear on the next whorl, but there appears a series of axial raised plicae that again disappears on the later whorls. The suture is deep and there is a small subsutural channel covered with minute axial ribs. Near this channel there are a few spiral minute spiral ribs, giving the area near the suture a reticulate aspect. The rest of the whorls is smooth, but under the microscope one observes tiny axial and spiral ribs. These continue on the base, but halfway the base appear a series of fine spiral ridges. The umbilicus is deep and there is a pronounced umbilical keel. Deep in the umbilicus we observe heavy crenulations on this keel around the first whorls. In the aperture, a thin nacreous layer which is rather heavily colored with mainly shades of green. The glossy shell is cream colored with a light brown pattern of regularly set flecks. Most specimens have a spiral line of interrupted brown and white spots in the center of the upper part of the whorls. The base is white with a pattern of brown flecks or flames that starts around the umbilical keel and rays out towards the border. Often a brown spiral line within the umbilicus.
Poppe, G.T. , Tagaro, S.P. & Dekker, H., 2006. The Seguenziidae, Chilodontidae, Trochidae, Calliostomatidae and Solariellidae of the Philippine Islands.
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 0.44xto 0.47x 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. 111), a smaller species from Indonesia which is not as depressed and has a more rounded aperture.
Vilvens, C. & Williams, S., 2020: New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific.

Interchangeable taxa

We compare M. gotoi with M fulgens Dall, 1907. The latter shell is much smaller, equally glossy but with a dominant olive green color instead of brown. The spire in M fulgens is higher and both species can be distinguished at once by the absence of a sharp umbilical keel in M. fulgens. Solariella zacalloides Schepman, 1908 is a synonym of M. fulgens.
Poppe, G.T. , Tagaro, S.P. & Dekker, H., 2006. The Seguenziidae, Chilodontidae, Trochidae, Calliostomatidae and Solariellidae of the Philippine Islands.

Distribution

TYPE LOCALITY
The Philippines, Aliguay Island.

DISTRIBUTION AND HABITAT
From the type locality north to offshore Batangas. Shells are dredged between 50 and 200 m deep.
Poppe, G.T. , Tagaro, S.P. & Dekker, H., 2006. The Seguenziidae, Chilodontidae, Trochidae, Calliostomatidae and Solariellidae of the Philippine Islands.
Philippines 50-200 m (Poppe et al, 2006); Eastern Indonesia, 181-184 m (dd) (Vilvens 2009).
Vilvens, C. & Williams, S., 2020: New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific.
Author: Jan Delsing

Links and literature

EN Galli C.: WMSDB - Wolrdwide Mollusc Species Data Base July 10, 2013 [http://www.bagniliggia.it/WMSD/WMSDhome....] [as Microgaza gotoi Poppe, Tagaro & Dekker, 2006]
Data retrieved on: 22 November 2013

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