Hungerfordia elegantissima anomphala M. Yamazaki and Ueshima

Yamazaki, Midori, Yamazaki, Kazunori, Rundell, J. & Ueshima, Rei, 2015, Systematic review of diplommatinid land snails (Caenogastropoda, Diplommatinidae) endemic to the Palau Islands. (3) Description of eight new species and two new subspecies of Hungerfordia, Zootaxa 4057 (4), pp. 511-538 : 525-527

Hungerfordia elegantissima anomphala M. Yamazaki and Ueshima subsp. nov.

(Figs. 7, 12T)

Material examined. Holotype. Metkerel a Chudel (Loc. Mc8-5), eastern part of Mecherchar island, Palau. Collected by R. U. and M. Y. on Sept. 28, 2006. UMUTZ-MG-B1285T. Paratypes: Mecherchar: Loc. Mc2-1, 36 specimens, 8/XI/2004, UMUTZ-MG-B0080; ditto, 17 specimens, 1/VII/2005, UMUTZ-MG-B0232; Loc. Mc8-5, 6 specimens, 28/II/2011, UMUTZ-MG-B1285.

Diagnosis. Shell similar to the nominal subspecies, but differs in the following features. Umbilicus closed in adult. Last 1/16–1/8 whorls attached to the previous whorl, never decoiled downward. Shell more slender. Spiny ribs above the aperture somewhat shorter than those on the preceding and following whorls. Distribution endemic to Mecherchar island.

Description. Shell (Figs. 7A–C, 12T). Shell sinistral, small for Hungerfordia species, slender conical, penultimate whorl widest (slightly wider than the last whorl) when removing the spiny ribs and the peristomes. Shell diameter including the spiny ribs almost equal to or slightly smaller than the shell height. Shell color yellow or white. Whorls 5.5–6, convex, obtusely angulate at the periphery on the penultimate whorl; last 1/16–1/8 whorls (behind the outer peristome) attached to the previous whorl, never decoiled downwards like the nominal subspecies, never ascending onto the penultimate whorl in left lateral view. Suture impressed. Constriction located at a half whorl behind the aperture, hardly recognizable in external view, but associated with very weak reduction of the spiny ribs in its length (height), internally without palatal plica except a low axial-crest caused by the constriction. Tuba a half whorl. Protoconch 1–1+1/8 whorls, almost smooth, finely and very weakly punctated on FIGURE 7. Hungerfordia elegantissima anomphala subsp. nov. (A1–9) A paratype, Loc. Mc2-1, B0080a: (A9) left lateral view of the last 2 whorls, note that the last 1/8 whorls are attaching to the penultimate whorl (never decoiled downward like the nominal subspecies); (B1–6) holotype, arrowheads indicate the position of the constriction, B1285T; (C) a partially broken specimen after removal of the spiny ribs, apical view, showing the position of the constriction (arrowhead), a paratype from Loc. Mc2-1, B0080b; (D1–2) outer surface, and (D3–4) inner surface of operculum, a paratype from Mc3-3, B0232. Arrowheads indicate the positions of the constriction. Scale bars, 1mm (A–C), 0.5 mm (D). All specimens, UMUTZ-MG.

lower whorl. Apical septum absent. Axial rib strongly developed on teleoconch, oblique to the coiling axis, strongly protruded as spines on most whorls: ribs on the initial 1/4 whorls of the teleoconch weak, low, moderately spaced, almost straight (not folded at the peripheries of the whorls); ribs on the subsequent whorls highly protruded as spines, strongly folded at the peripheries of the whorls, widely spaced (10–12 ribs in a whorl); upper margin of the ribs above the spiny projections (between the suture and spines) low, very slightly elevated or indistinct; lower (basal) margin of the ribs below the spines prominently protruded at the base of the last whorl, gradually decreased in the height towards the umbilicus; spiny projections of the ribs very long, weakly pointed, slender, strongly folded, obliquely depressed, narrow, arising at some distance below the suture (near the peripheries of the whorls), abruptly reduced in height just below the peripheries of the whorls (but still shortly protruded and extended to the suture of the next whorl), protruded slightly upward on the upper whorls, becoming protruded horizontally or downward on the last whorl, upper margin folded over the lower margin, with fine spiral sculptures on the outer surface; ribs above the aperture (ribs on the last 1 to last 2/3 whorls) showing a slight change of the ribbing pattern, though still retaining developed spiny projections, but with shorter spiny projections and slightly more closely spaced than those on the preceding and following whorls. Interspace between the spiny ribs almost smooth, without prominent axial sculpture except some faint growth lines on the last 1/2 whorls. Spiral sculptures present throughout the teleoconch, fine, weak, extended onto the outer surface of the spiny ribs and the outer peristome, sinuous in high magnification. Base slightly convex, without basal keel, with shortly protruded axial ribs. Umbilicus closed in adult. Axial protrusion of shell wall (along the spiny ribs) hardly developed. Aperture evidently tilted downward against the coiling axis (in left lateral view), shortly protruded downward from the upper body whorl. Columellar tooth very weak, reduced to a very low swelling of columella, which is gradually thickened from the parietal roof, recessed inside the aperture, short. Peristome double. Outer peristome widely expanded beyond the inner one at the palatal, basal and lower columellar sides, abruptly reduced at base of the columellar side to form a rounded baso-columellar edge, undeveloped on the parietal and upper columellar sides, thin, with fine and concentric growth lines on the inner surface. Inner peristome squarish circular, moderately expanded at the lower palatal, basal, and columellar sides, hardly expanded (in front view) but slightly extended forward at the parietal side, only slightly protruded from the outer peristome at the palatal and basal sides, elected and free from the base of the last whorl at the columellar side; parietal margin shortly separated downward from the upper body whorl. Interspace between the inner and outer peristomes very narrow.

Dimensions. Shell height 3.5–4.1 mm, diameter 3.1–4.0 mm, suture width 1.5–1.6 mm, apertural height 1.1– 1.2 mm.

Operculum (Figs. 7D1–4). Operculum corneous, multispiral, circular, rather thin, transparent, amber colored, flat or slightly concave; outer surface smooth; inner surface with a strongly developed arcuate ridge near the columellar margin; arcuate ridge very thick, highly protruded, somewhat wavy at the edge, lateral processes much less developed than the nominal subspecies.

Penis. Penis absent.

Radula . Not examined..

Distribution and ecology. Endemic to Palau: Mecherchar island. The species inhabits limestone rocks.

Remarks. H. elegantissima anomphala differs from the nominal subspecies in the following points (Figs. 12T, U): the umbilicus is closed in adult; the last 1/8 whorls is attached to the pervious whorl, never decoiled downward, although the aperture itself is shortly protruded downward; the aperture is not so strongly turned downward; the shell is more slender; the spiny ribs above the aperture are shorter and more closely spaced than those on the preceding and following whorls. The distribution of H. elegantissima anomphala is endemic to Mecherchar island.

Etymology. The subspecific name, derived from Latinized Greek, a + omphalus, refers to the closed umbilicus.