Hungerfordia chilorhytis 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 : 532-534

Hungerfordia chilorhytis M. Yamazaki and Ueshima sp. nov.

(Figs. 10, 12E)

Material examined. Holotype. Belual a kelat, a northern islet of Ngemelis islands (Loc. Gm7-1), Palau. Collected by R. U. and M. Y. on Jan. 28, 2010. UMUTZ-MG-B0944T. Paratypes. Ngemelis: same data as holotype, 28 specimens, UMUTZ-MG-B0944.

Diagnosis. Shell sinistral, small for Hungerfordia species, slender conical or fusiform. Last 3/4 whorls characteristically sculptured by strong dorsal grooves. Shell color yellow. Axial ribs low, closely spaced on most whorls (higher than the last 3/4 whorls), irregularly spaced and partially indistinct on the last 3/4 whorls. Spiral sculpture present throughout teleoconch whorls. Dorsal grooves strongly developed on the last 3/4 whorls, axial (parallel to the axial ribs), 5–6, deeply impressed, widely spaced. Interspace between the axial grooves convex, somewhat protruded like “axial folds”, with 2–5 of ribs on its surface. Base convex, with a prominent circumcolumellar fold; circum-columellar fold strongly developed, almost radially straight in umbilical view. Outer peristome absent. Inner peristome somewhat distorted, obtusely angulate at the periphery, squarish circular, with a characteristic baso-palatal lip. Baso-palatal lip developed along the palatal and basal margin of the inner peristome, a ridge-like thickening, abtuptly truncated at a short distance before the columella (at the base), leaving a canal-like depression at the baso-columellar edge of the inner peristome. Columellar tooth moderately developed. Thickened lip developed behind the aperture, wide; dorsal margin distinct; palatal side abruptly expanded from the preceding whorl, then gradually narrowed toward the aperture in umbilical view. Endemic to an islet of Ngemelis islands.

Description. Shell (Figs. 10A–C, 12E). Shell sinistral, thick, small for Hungerfordia species, slender conical or fusiform, penultimate whorl widest when excluding the thickened lip; sides almost straight or slightly concave on the upper whorls, convex on the last 2 whorls. Shell color yellow. Whorls 6–6.5, convex, broadest (in longitudinal width) on the penultimate or the last whorl in dorsal view: last 3/4 whorls characteristically sculptured, with strong axial dorsal grooves; last 1/8 whorls (including the thickened lip) expanded upward, ascending onto the penultimate whorl in left lateral view. Suture impressed. Constriction located above the parietal/columellar junction of the aperture, internally without palatal plica except a low, axial crest caused by the constriction, without FIGURE 10. Hungerfordia chilorhytis sp. nov. (A1–8) A topotypic paratype, Loc. Gm7-1, B0944a: (A7) aperture, showing the developed baso-palatal lip of the inner peristome; (B1–6) holotype, B0944T; (C) a topotypic paratype, B0944b; (D1–2) outer surface, and (D3–4) inner surface of operculum, a topotypic paratype, B0944c. Scale bars, 1mm (A1–6, A8, B, C), 0.5 mm (A7, D). All specimens, UMUTZ-MG.

parietal tooth. Tuba 7/8 whorls. Protoconch 1–1+1/8 whorls, almost smooth, very weakly and finely punctated on the lower part of whorl. Apical septum absent. Axial ribs present on teleoconch, almost straight (never folded at the peripheries of the whorls), oblique to the coiling axis: ribs on most whorls (higher than the last 3/4 whorls) distinct, closely spaced (13–22 ribs in a quarter whorl), low; ribs on the last 3/4 whorl irregularly spaced, partially indistinct. Dorsal grooves strongly developed on the last 3/4 whorls, axial (parallel to the axial ribs), deeply impressed, 5–6, widely spaced, arising at short distance below the suture, becoming weaker toward the columella, internally protruded as “axial folds” within the aperture. Interspace between the dorsal grooves convex, somewhat protruded like “axial dorsal folds”, wide, frequently edged along a rib in umbilical view, with 2–5 ribs on its surface, also with short and closely spaced growth lines or reduced ribs just below the suture. Spiral sculpture present on teleoconch, continued throughout whorls, but somewhat weakened on the last 3/4 whorls, fine, rather prominent, sinuous in high magnification. Base rather convex, with a prominent circum-columellar fold; circumcolumellar fold rather strongly developed on the last 3/4 whorls, almost radially straight in umbilical view, extended along the columellar side of the thickened lip, strongest and broadest just after the constriction, then gradually becoming weaker toward the columella. Umbilicus closed in adult. Aperture not protruded, slightly tilted downward against the coiling axis in left lateral view; columellar axis within aperture almost vertical. Columellar tooth moderately developed, emerged at the aperture, but never extended onto the inner peristome, deeply extended inward about 3/4 whorls. Peristome single. Outer peristome never developed at the dorsal margin of the thickened lip. Inner peristome characteristically shaped and sculptured, squarish circular, obtusely angulate at the periphery, moderately expanded at the parietal, columellar, and basal sides, depressed and less expanded at the upper palatal side (in front view), with a characteristic baso-palatal lip; parietal margin located below the middle level of the upper body whorl. Baso-palatal lip developed along the palatal and basal margin of the inner peristome, a ridgelike thickening which is continued from the angular edge to the base of the inner peristome, strongly developed at the base, but abtuptly truncated at a short distance before the columella (at the base), leaving a canal-like depression at the baso-columellar edge of the inner peristome (in umbilical view), with fine glanular sculptures on its surface. Thickened lip developed behind the aperture, rather wide in left lateral view, expanded beyond the inner peristome in front view, white, lacking of periostracum, with fine growth lines on its outer surface; palatal side slightly or hardly narrowed toward the aperture in umbilical view; dorsal margin distinct, abruptly expanded from the preceding whorl at the palatal side; uppermost margin (= suture) ascending onto the penultimate whorl toward the aperture in left lateral view; base extended almost horizontally or slightly ascending toward the aperture in left lateral view; palatal margin somewhat protruded beyond the penultimate whorl in apical view.

Dimensions. Shell height 2.8–3.2 mm, shell diameter 1.7–2.0 mm, suture width 1.4–1.6 mm, peristome height 0.9–1.1 mm.

Operculum (Figs. 10D1–4). Operculum corneous, multispiral, circular, semi-transparent, amber-colored, thin, flat; outer surface smooth; inner surface with a low, C-letter shaped ridge at the columellar side.

Penis. Penis absent.

Distribution and ecology. Endemic to Palau: Belual a kelat, a northern islet of Ngemelis islands. The species inhabits limestone rocks.

Remarks. H. chilorhytis is similar to H. crenata Yamazaki & Ueshima, 2015 in the sculpture and the ribbing pattern, but differs in the distinctly larger shell size and the presence of a baso-palatal lip inside the inner peristome (Figs. 12D, E).

Eymology. The species name derived from Latinized Greek, cheilos + rhytis, refers to the inner peristome with a characteristic baso-palatal lip.