Hungerfordia goniobasis dmasechensis K. Yamazaki and Ueshima, 2013

YAMAZAKI, KAZUNORI, YAMAZAKI, MIDORI & UESHIMA, REI, 2013, <p> <strong> Systematic review of diplommatinid land snails (Caenogastropoda, Diplommatinidae) endemic to the Palau Islands. (1) Generic classification and revision of <em> Hungerfordia </ em> </ strong> <br /> <strong> species with highly developed axial ribs </ strong> </ p>, Zootaxa 3743 (1), pp. 1-71 : 42-44

Hungerfordia goniobasis dmasechensis K. Yamazaki and Ueshima subsp. nov.

( Figs. 9I , 20 , 29L )

Materials examined. Holotype. Dmasech islet of Ngemelis islands (Loc. Gm5-2), Palau. Collected by R. U. and K. Y. on Nov. 16, 2006. UMUTZ-MG-B0579 T . Paratypes. Ngemelis: Loc. Gm5-2, 23 specimens, 16/XI/2006, UMUTZ-MG-B0579; ditto, 21 specimens, 24/X/2007, UMUTZ-MG-B0796 .

Diagnosis. Shell generally similar to H. goniobasis goniobasis , but differs by the following features. Axial ribs more closely spaced than the nominal subspecies. Interspace between the axial ribs with characteristic growth wrinkles; growth wrinkles developed below the suture, coarse, distnctly flared. Aperture larger than the nominal subspecies; parietal margin of the inner peristome attaching to (not separated downward from) the base of the upper body whorl. Distribution endemic to Dmasech islet of Ngemelis islands.

Description. Shell ( Figs. 20A–H , 29L ). Shell sinistral, small for Hungerfordia species , slender conical, last whorl widest when removing the protruded ribs. Shell color white or yellowish brown, apical whorls occasionally yellow with the color becoming deeper toward the apex. Whorls 7–7.5, regularly coiled (increasing regularly in both width and height), convex in apical whorls, obtusely angulate at periphery of the spiny ribs on lower whorls; last 1/8 whorls expanded downward, never ascending onto the penultimate whorl in left lateral view except a short upward extension of the outer peristome. Suture impressed. Constriction located above the parietal/columellar junction of the aperture, less prominent in external view, associated with a weak reduction of the spiny ribs, internally without palatal plica except a low axial-crest caused by the constriction. Tuba 7/8–3/4 whorls. Apical septum absent. Protoconch 1.25–1.5 whorl, punctated. Axial ribs developed on the teleoconch, oblique to the coiling axis, strongly developed as spines on most whorls; ribs undeveloped on the first 1/8–1/3 whorls of the teleoconch; ribs on the following 1/8 whorls of initial teleoconch low, closely spaced, not folded; ribs on the subsequent whorls highly protruded as spines, widely spaced (10–12 ribs in a whorl), not synchronized with those on the previous whorls, folded at the periphery; upper margin of the ribs above the spiny projection (between the periphery and spines) low, indistinct or slightly elevated; spiny projections of the ribs very high, weakly pointed, trough-shaped, slightly curved upward on the upper whorls, becoming gradually protruded laterally or rather downward on the last whorl, rather narrow, arising at some distance below the suture (near periphery of a whorl), upper margin folded over the lower margin, lower margin extended below to the suture of the next whorl, with fine spiral sculptures on the outer surface; ribs above the aperture (ribs on the last 1 to last 3/4 whorls around the constriction) more closely spaced than those on the preceding and following whorls, with slightly lower but still developed spiny projections. Interspace between the spiny ribs with characteristic growth wrinkles; growth wrinkles developed below the suture on the last 3–4 whorls, coarse, shortly but distinctly protruded, somewhat lamellar, white. Spiral sculptures present through the teleoconch, fine, prominent, extended on outer surface of the spiny ribs and outer peristome, sinuous in higher magnification. Base with a strong basal keel. Basal keel developed at the base of the last 3/4 whorls, strong, with a rather sharp edge, arising just after the constriction, continued to the outer peristome, with a series of fine growth lines at the columellar side. Umbilicus closed in adult. Axial protrusions of shell wall (along the ribs) developed on the last whorl. Aperture of usual size, tilted downward against the coiling axis, located below base of the upper body whorl, hardly protruded, recessed inside the outer peristome; columellar axis within aperture almost vertical. Columellar tooth present, weak but more developed than the nominal subspecies, low, visible within the aperture, located near the base of the columella. Peristome double: outer peristome tilted downward against the coiling axis, widely expanded beyond the inner one at the palatal and basal sides, extended latero-basally like a spatula in dorsal view, with a series of fine growth lines on the inner surface, with fine spiral sculptures on the outer surface; inner peristome squarish circular, hardly protruded from the outer one, weakly expanded at the lower palatal, basal and columellar sides, erected from the basal keel at the columellar side to form a narrow “pseudo-umbilicus”; parietal margin of inner peristome almost horizontal, never expanded onto the upper body whorl, located just below the base of the upper body whorl.

Dimensions. Shell height 3.1–3.4 mm, diameter 2.0–2.3 mm, suture width 1.2–1.4 mm, peristome height 0.8– 0.9 mm.

Operculum ( Figs. 20I 1 –I 4 ). Operculum corneous, multispiral, circular, transparent, amber colored, thin, flat; outer surface smooth; inner surface with a low, weak, arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula ( Fig. 9I ). Radula of specialized type of taenioglossate; ribbon very long. Central tooth very large with a very wide, large and blunt central cusp, with a pair of small lateral cusps; lateral teeth also large, with a very large major cusp, with a small inner cusp, without outer cusp; inner marginal teeth with a large major cusp, with two slender inner cusps, with a short outer cusp; outer marginal teeth with a large and blunt major cusp, two slender inner cusps, without outer cusp.

Distribution and ecology. Endemic to Palau: Dmasech islet of Ngemelis islands. The subspecies inhabits vertical walls of large limestone rocks or limestone rubbles.

Remarks. H. goniobasis dmasechensis differs from the nominal subspecies by the presence of coarse growth wrinkles below the suture between the spiny ribs, having a larger (normal sized) aperture, the parietal margin of the inner peristome being attached to base of the upper body whorl, the more closely spaced axial ribs, and the broader shell shape. The distribution of the subspecies is restricted to Dmasech islet.

Etymology. Named after the type locality, Dmasech islet.

Figures

FIGURE 1. Map of Palau islands showing collecting sites. Small red circles show collecting sites. Areas encircled by blue rectangles are shown as enlarged maps in Figs. 2–5. Abbreviations of the collecting sites are listed in Table 2.

FIGURE 9. Radulae of Hungerfordia species. (A) H. pelewensis Beddome, 1889, B0283; (B) H. triplochilus sp. nov., topotypic paratype, B0158; (C) H. expansilabris sp. nov., topotypic paratype, B1299; (D) H. nudicollum sp. nov., topotypic paratype, B0364; (E) H. echinata echinata sp. et subsp. nov., paratype, B1084; (F) H. echinata tubulispina subsp. nov., topotypic paratype, B0169; (G) H. elegantissima sp. nov., topotypic paratype, B0375; (H) H. goniobasis goniobasis sp. et subsp. nov., topotypic paratype, B0235; (I) H. goniobasis dmasechensis subsp. nov., topotypic paratype, B0579; (J) H. lamellata (Crosse, 1866), B0157; (K) H. subalata sp. nov., paratype, B0021; (L) H. pteropurpuroides sp. nov., topotypic paratype, B1116; (M) H. alata (Crosse, 1866), B1041; (N) H. papilio papilio sp. et subsp. nov., paratype, B0374; (O) H. papilio stenoptera subsp. nov., paratype, B0761. Scale bars, 10 µm. All specimens, UMUTZ-MG.

FIGURE 20. Hungerfordia goniobasis dmasechensis subsp. nov. (A1–A5) A topotypic paratype, B0579a; (B) aperture, (C) columellar tooth (dorsal view), (D) axial ribs above the aperture, and (E) sculpture on the penultimate whorl (left lateral view) of topotypic paratypes (B0579a, b); (F) sculpture on the penultimate whorl of the holotype; (G1–G5) holotype, B0579T; (H) a topotypic paratype, B0579c; (I1, I2) outer surface, and (I3, I4) inner surface of operculum, a topotypic paratype, B0579. Scale bars 1mm (A, G–H), 0.5 mm (B–F, I). All specimens, UMUTZ-MG.

FIGURE 29. Shell size and shape variation among Hungerfordia species with highly developed ribs. (A) H. triplochilus sp. nov., holotype; (B) H. expansilabris sp. nov., holotype; (C) H. nudicollum sp. nov., holotype; (D) H. echinata echinata sp. et subsp. nov., holotype; (E) H. echinata tubulispina subsp. nov., holotype; (F1) H. lamellata (Crosse, 1866), B0199a; (F2) H. lamellata (Crosse, 1866), B0282b; (G) H. alata (Crosse, 1866), B0446; (H) H. pteropurpuroides sp. nov., holotype; (I1) H. subalata sp. nov., paratype (B0655); (I2) H. subalata sp. nov., holotype; (J) H. papilio stenoptera subsp. nov., holotype; (K) H. papilio papilio sp. et subsp. nov., holotype; (L) H. goniobasis dmasechensis subsp. nov., holotype; (M) H. goniobasis goniobasis sp. et subsp. nov., holotype; (N) H. elegantissima sp. nov., holotype; (O1) H. pelewensis Beddome, 1889, B0542; (O2) H. pelewensis Beddome, 1889, B0383. Scale bar, 1mm. All specimens, UMUTZ-MG.

FIGURES 4–5. Enlarged maps of Palau islands showing collecting sites. Top (Fig. 4), map of Ngerkutabel island and its neighboring islands or islets; bottom (Fig. 5), map of Mecherchar island and its neighboring islands or islets. Abbreviations of the collecting sites are listed in Table 2.