Hungerfordia fragilipennis 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 : 520-522

Hungerfordia fragilipennis M. Yamazaki and Ueshima sp. nov.

(Figs. 5, 12R1–2)

Materials examined. Holotype. Eastern slope in front of Ngkur (Loc. Gk6-2), northern Ngeruktabel island, Palau. Collected by R. U. on Oct. 22, 2007. UMUTZ-MG-B0737T. Paratypes. Ngeruktabel: Loc. Gk6-2, 56 specimens, 22/X/2007, UMUTZ-MG-B0737; Loc. Gk7-6, 11 specimens, 30/I/2010, UMUTZ-MG-B1004, 1012; Loc. Gk7-7, 2 specimens, 30/I/2010, UMUTZ-MG-B1024; Loc. Gk7-8, 8 specimens, 30/I/2010, UMUTZ-MG-B1034.

Diagnosis. Shell sinistral, very large for Hungerfordia species, subconical with almost cylindrical last 2 whorls. Shell color transparent, upper whorls occasionally yellow-colored. Constriction located above the aperture, associated with disappearance of the wing-like ribs. Apical septum present. Apical whorls frequently decollated in adult. Axial ribs on most whorls strongly protruded as wings, very widely spaced; wing-like projections of the ribs high, very wide, arising at the suture, extended below to the suture of the next whorl, thin, very fragile, frequently broken or lost in adult; ribs above the aperture abruptly becoming closely spaced and very low, without any winglike projections. Interspace between the wing-like ribs almost smooth, polished, with fine and short growth wrinkles below the suture on the last 1.5-3/4 whorls. Spiral sculptures absent on most whorls. Umbilicus closed or very narrowly open. Aperture hardly or slightly tilted upward against the coiling axis. Columellar tooth very weak. Peristome double. Outer peristome strongly developed, widely expanded beyond the inner peristome in front view. Inner peristome squarish circular, widely expanded. Interspace between the inner and outer peristomes wide.

Description. Shell (Figs. 5A–E, 12R1–2). Shell sinistral, very large for Hungerfordia species, rather thin for winged Hungerfordia species, subconical with almost cylindrical last 2 whorls, penultimate whorl widest (last 2 whorls almost equally widest, but penultimate whorl slightly wider than the last whorl) when removing the protruded ribs and peristomes. Apical whorls (above the apical septum) frequently decollated in adult. Shell color transparent, upper whorls occasionally yellow-colored with the color becoming deeper towards the apical septum, apical whorls above the septum always uncolored. Whorls 6–7, convex on apical whorls, less convex on the last 2– 3 whorls; last 1/16–1/8 whorls (including the interspace between the outer and inner peristomes) expanded upward and ascending onto the penultimate whorl in left lateral view. Suture impressed. Constriction located above the parietal/columellar junction of the aperture, associated with abrupt changes of the ribbing pattern, internally without palatal plica except a low axial-crest caused by the constriction. Tuba 7/8 whorls. Protoconch 1+1/4 whorls, almost smooth, very weakly and very finely punctated on the lower whorl. Apical septum present, constructed inside the apical whorls, constructed between a half whorl before and a half whorl after the protoconch/ teleoconch boundary. Axial ribs developed on the teleoconch, highly developed as wings on most whorls: ribs undeveloped on the first 1/16 whorls of the teleoconch; ribs on the following 1/4 whorls of initial teleoconch weak, rather moderately spaced, very low, without wing-like projections; ribs on the subsequent whorls except above the aperture (ribs on most whorls except above the aperture) strongly developed, widely and highly protruded as “wings”, very widely spaced (9–12 ribs in a whorl), not synchronized with those on the previous whorls, with simply curved or very weakly angulate base-lines, weakly elevated by axial protrusions of shell wall along the ribs; wing-like projections of the ribs lamellar, high, thin, very fragile, frequently broken or lost in adult, very wide, arising at the suture, extended below to the suture of the next whorl, weakly curved or very faintly folded at the peripheries of the whorls, very weakly pointed with a rounded edge, protruded slightly upward on most whorls, becoming protruded rather downward on the last 3/4 whorls; ribs above the aperture (ribs on the last 1+1/8–1 whorls to the last 3/4 whorls around the constriction) abruptly becoming very closely spaced and very low, without any wing-like projection, weak, fine. Interspace between the wing-like ribs almost smooth, glossy, without any axial sculpture except some faint growth lines on most whorls, with fine and short growth wrinkles below the suture on the last 1.5–3/4 whorls (except above the aperture). Spiral sculptures almost undeveloped on the teleoconch, very faintly and very finely developed only on the initial 1/2–1 whorls of teleoconch, absent on the subsequent whorl (most teleoconch whorls). Base convex, without basal keel. Axial protrusions of shell wall (along the ribs) hardly developed on the last 3/4 whorls, very weak in umbilical view (visible after removal of the winged ribs). Umbilicus very narrowly opened or closed in adult, though hidden by the winged ribs in fresh specimens. Aperture hardly or slightly tilted upward against the coiling axis (in left lateral view), weakly protruded from the previous whorl; columellar axis within aperture almost vertical. Columellar tooth very weakly developed, very low, penetrated inward about 3/4 whorls. Peristome double, expanded. Outer peristome strongly developed, widely expanded beyond the inner peristome in front view, occasionally with a rounded baso-columellar edge, reflexed backward, abruptly expanded from the preceding whorl; inner surface smooth, polished, with fine concentric growth lines. Inner peristome squarish circular, widely expanded in all around (particularly at the parietal side), widely separated and protruded from the outer peristome, somewhat thickened and weakly reflexed; parietal margin located below or near the middle level of the upper body whorl. Interspace between the inner and outer peristomes rather wide, with very fine growth wrinkles or riblets on the outer surface; uppermost margin (= suture) ascending onto the penultimate whorl toward the aperture in left lateral view; base also ascending toward the aperture in left lateral view.

Dimensions. Shell height 6.0 to> 6.6 mm (the largest specimen has a partially decollated apex), diameter 3.7– 4.3 mm, suture width 2.5–2.7 mm, peristome height 2.0– 2.5 mm.

Operculum (Figs. 5F1–4). Operculum corneous, multispiral, circular, transparent, amber colored, thin, flat or slightly concave; outer surface smooth; inner surface with a low, weak, arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula . Not examined.

Distribution and ecology. Endemic to Palau: Eastern coast of northern part of Ngeruktabel island. The species frequently inhabits vertical walls of large limestone rocks, occasionally on limestone rubble.

Remarks. H. fragilipennis is most similar to H. papilio stenoptera Yamazaki & Ueshima, 2013 (Figs. 12R, S), but differs in the following points: the wing-like ribs are shorter, more fragile (frequently lost), and never synchronized with those on the previous whorls even on the apical whorls; the apical septum is present; the apical whorls above the septum is frequently decollated; the shell is larger, broader, and thinner; the umbilicus is distinctly narrower. H. fragilipennis is unique among winged Hungerfordia species in having rather thin shell, which is responsible for the very fragile wing-like ribs and the frequently decollated apical whorls.

Etymology. The specific name, derived from Latin fragilis and pennis, refers to the very fragile wing-like ribs.

FIGURE 5. Hungerfordia fragilipennis sp. nov. (A1–6) A topotypic paratype, Loc. Gk6-2, B0737a; (B) apical whorls of a decollated specimen, showing the apical septum, a topotypic paratype, B0737b; (C1–6) holotype, note that the wing-like projections of the ribs are completely lost and that the apical whorls are decollated, B0737T; (D) yellowish variant, a topotypic paratype, B0737c; (E1–4) a paratype from Loc. Gk7-6, a specimen with well preserved wing-like ribs and a complete apex, B1012; (F1–2) outer surface, and (F3–4) inner surface of operculum, a topotypic paratype, B0737. Scale bars, 1mm (A, C–E), 0.5 mm (B, F). All specimens, UMUTZ-MG.