Hungerfordia expansilabris 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 : 27-28

Hungerfordia expansilabris K. Yamazaki and Ueshima sp. nov.

( Figs. 9C , 14 , 29B )

Material examined. Holotype. East of Pkulaklim islet (Loc. BA 5-5), Airai state, Babeldaob island, Palau. Collected by R. U. and K. Y. on Nov. 12, 2006. UMUTZ-MG-B0480 T . Paratypes. Babeldaob: Loc. BA 6-1, 13 specimens, 21/X/2007, UMUTZ-MG-B0667; Loc. BA 8-3, 6 specimens, 1/III/2011, UMUTZ-MG-B1309; Loc. BA 8-4, 3 specimens, 1/III/2011, UMUTZ-MG-B1322. Pkulaklim islet: Loc. BA 5-4, 1 specimen, 12/XI/2006, UMUTZ-MG-B0472; Loc. BA 5-5, 6 specimens, 12/XI/2006, UMUTZ-MG-B0480; ditto, 58 specimens, 1/III/ 2011, UMUTZ-MG-B1299; Loc. BA 6-2, 21 specimens, 21/X/2007, UMUTZ-MG-B0672 .

Diagnosis. Shell sinistral, medium-size for Hungerfordia species , slender conical. Shell color white or yellow. Constriction located above the aperture, followed by an abrupt swelling of whorl, associated with abrupt reduction of the spiny ribs. Axial ribs on most whorls highly protruded as spines, strongly folded at the periphery, widely spaced; upper margin of the ribs above the spiny projections (between the suture and spines) low, indistinct; spiny projections of the ribs very high, rather narrow, arising at some distance below the suture, folded at the periphery; ribs above the aperture very low and closely spaced, almost hidden by the expanded inner peristome. Spiral sculptures fine. Axial protrusions of shell wall (along the ribs) strongly developed on the last 3/4 whorls. Aperture strongly protruded, hardly tilted. Columellar tooth absent. Peristome usually double, very widely and extremely expanded, thin, fragile; outer peristome very widely expanded beyond the inner one at the palatal and basal sides, with rounded upper-palatal and baso-columellar edges, columellar margin strongly folded backward and covering the umbilicus; inner peristome very widely expanded all around, circular, parietal margin expanded beyond the middle level of the upper body whorl. Interspace between the outer and inner peristomes wide, abruptly expanded towards the aperture, almost smooth on its outer surface.

Description. Shell ( Figs. 14A–H , 29B ). Shell sinistral, medium-size for Hungerfordia species , slender conical, last whorl widest when removing the expanded ribs and peristomes. Shell color semi-transparent, white or light yellow, apical whorls occasionally yellow with the color becoming deeper toward the apex. Whorls 6–7, slightly convex; last 1/8 whorls (including interspace between the outer and inner peristomes) expanded upward and ascending onto the penultimate whorl in left lateral view. Suture weakly impressed. Constriction located above the parietal/columellar junction of the aperture, followed by an abrupt swelling of whorl, associated with abrupt reduction of the spiny ribs, internally without palatal plicae except a low axial-crest caused by the constriction. Tuba 7/8 whorls. Protoconch 1.5–2 whorls, apical whorl smooth, lower whorl faintly punctated below the suture. Apical septum absent. Axial ribs developed on the teleoconch, oblique to the coiling axis, strongly protruded as spines on most whorls; ribs on the first 1/2 to 3/4 whorls of the teleoconch low, closely spaced, not folded, gradually becoming higher and widely spaced; ribs on the subsequent whorls (except above the aperture) highly protruded as spines, strongly folded at the periphery, widely spaced (10–12 ribs in a whorl), not synchronized with those on the previous whorls; upper margin of the ribs above the spiny projection (between the suture and spines) low, indistinct or faintly elevated; spiny projections of the ribs very high, weakly pointed, narrow, arising at some distance below the suture (arising near periphery of a whorl), folded at the periphery, trough-shaped, protruded slightly upward or laterally on upper whorls, becoming to protruded rather downward on the last half whorl, upper margin weakly 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 the last 3/4 whorls around the constriction) abruptly becoming closely spaced and very low, without spiny projections, gradually becoming less folded at the periphery, almost hidden by the expanded inner peristome. Interspace between the spiny ribs without prominent axial sculpture on upper whorls, with coarse growth wrinkles below the suture on the last 3/4 whorls. Spiral sculptures present throughout the teleoconch, fine, rather prominent, expanded on the outer surface of the spiny ribs and outer peristome, sinuous in high magnification. Base convex, without basal keel. Umbilicus closed in adult by columellar reflection of the outer peristome not by narrowing of umbilical area. Axial protrusions of shell wall (along the ribs) very strongly developed on the last 3/4 whorls, hidden by the spiny ribs, strongest just after the constriction, becoming weaker toward the aperture, with rather deep axial depressions between them, adapertural side steep, abapertural side strongly convex and much wider than the adapertural one in umbilical view. Aperture hardly tilted against the coiling axis, strongly protruded; columellar axis within the aperture almost vertical. Columellar tooth usually absent, occasionally appeared as a faint columellar swelling. Peristome usually double, rarely triple with doubled inner peristome, very widely and extremely expanded; outer peristome thin, fragile, very widely expanded beyond the inner one at the palatal and basal sides, abruptly narrowed towards angular and columellar side to form rounded upper-palatal and baso-columellar edges, reflected backward, columellar margin strongly folded backward and covering the umbilicus, smooth and polished on the inner surface; inner peristome strongly protruded from the outer one, extremely widely expanded all around, especially on columellar and parietal sides, thin, very fragile, circular, parietal margin frequently expanded beyond the middle level of the upper body whorl; distal inner peristome usually undeveloped, weak and narrower than the proximal one when present. Interspace between the outer and inner peristomes wide, strongly expanded towards the aperture, outer surface almost smooth; uppermost margin continuously ascending toward the aperture in left lateral view, frequently with a series of very short growth wrinkles; base extended almost horizontally and then abruptly expanded toward the aperture in left lateral view.

Dimensions. Shell height 4.7–5.3 mm, diameter 3.2–3.8 mm, suture width 1.5–2.1 mm, peristome height 2.1– 2.6 mm.

Operculum ( Figs. 14I 1 –I 4 ). Operculum corneous, multispiral, circular, thin, amber colored, transparent, flat or weakly concave; outer surface smooth; inner surface with a low, C-letter shaped, arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula ( Figs. 9C ). 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 cups, basal plate longitudinally elongated and strongly constricted at the base. Lateral teeth also large, with a large, very wide and blunt major cusp, with or without a vestigial inner cusp, without outer cusp, basal plate obliquely elongated. Inner marginal teeth shorter than the lateral teeth, elongated, with a large major cusp, with two slender inner cusps and a small outer cup. Outer marginal teeth with a large, wide and blunt major cusp, with two slender inner cusps, without outer cusp.

Distribution and Ecology. Endemic to Palau: Babeldaob island (southern coastal limestone area) and its satellite islet, Pkulaklim. The species inhabits vertical walls of large limestone rocks or cliffs, occasionally on limestone rubbles.

Remarks. H. expansilabris is most similar to H. triplochilus , but differs from the latter by the much wider and fragile peristomes, the absence of a columellar tooth, the smooth interspace between the outer and inner peristomes, the absence or poor development of the distal inner peristome, and the axial protrusions of shell wall on the last 3/4 whorls being strongly developed. H. expansilabris is also distinguished from a sympatric congener, H. echinata , by having more widely spaced ribs, more slender spire, much wider and fragile peristomes, and the absence of a columellar tooth.

Etymology. The specific name, derived from Latin expansus (= expanded) and labrum (= lip), refers to the very widely expanded inner peristome.

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 14. Hungerfordia expansilabris sp. nov. (A1–A4) A topotypic paratype, B0480a; (B) columella (left lateral view), a paratype from Loc. BA6-1, B0667a; (C) axial ribs above the aperture after removal of the parietal margin of inner peristome, (D1) sculpture on the penultimate whorl, and (D2) sculpture on the body whorl of a topotypic paratype (B0480a); (E) umbilical view of a paratype after removal of the spiny ribs and the outer peristome, only the last whorl shown, Loc. BA6-1, B0667b; (F1–F5) holotype, B0480T; (G) a paratype from Loc. BA5-4, B0472; (H) a paratype from Loc. BA6-1, B0667c; (I1, I2) outer surface, and (I3, I4) inner surface of operculum, a topotypic paratype, B0480. Scale bars, 1mm (A–H), 0.5 mm (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.