Hungerfordia nudicollum 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 : 30-32

Hungerfordia nudicollum K. Yamazaki and Ueshima sp. nov.

( Figs. 9D , 15 , 29C )

Materials examined. Holotype. An unnamed islet north of Ongael (Loc. Gk4-2), northern side of Ngeruktabel island, Palau. Collected by R. U. and K. Y. on July 10, 2006. UMUTZ-MG-B0364 T . Paratypes. Ngeruktabel: Loc. Gk4-4, 4 specimens, 11/VII/2006, UMUTZ-MG-B0384; Loc. Gk2-2, 1 specimen, 12/VII/2006, UMUTZ- MG-B0435; Loc. Gk7-2, 6 specimens, 27/I/2010, UMUTZ-MG-B0912; Loc. Gk8-4, 2 specimens, 2/III/2011, UMUTZ-MG-B1344; Loc. Gk8-5, 2 specimens, 2/III/2011, UMUTZ-MG-B1358. Ngermedai islet, Ngeruktabel: Loc. Gk7-1, 4 specimens, 27/I/2010, UMUTZ-MG-B0903. Ongael and other satellite islet of Ngeruktabel: Loc. Gk1-2, 4 specimens, 28/V/2003, UMUTZ-MG-B0032; ditto, 5 specimens, 10/XI/2004, UMUTZ-MG-B0146; ditto, 8 specimens, 10/VII/2006, UMUTZ-MG-B0347; Loc. Gk4-2, 29 specimens, 10/VII/2006, UMUTZ-MG- B0364 .

Diagnosis. Shell sinistral, medium-size for Hungerfordia species , very slender conical. Shell color white. Constriction located above the aperture, associated with abrupt reduction of the spiny ribs. Axial ribs on most whorls strongly developed as tubular or folded spines, curled or strongly folded at the periphery, very widely spaced; upper margin of the ribs above the spines (between the suture and spines) very low, indistinct; spiny projections of the ribs very high, trough-shaped or almost tubular, rather narrow, arising at some distance below the suture; ribs above the aperture low, closely spaced, with greatly reduced spiny projections, hidden by the expanded inner peristome. Spiral sculptures fine. Aperture strongly protruded. Columellar tooth very weak. Peristome single; outer peristome absent; inner peristome very widely expanded all around, circular, with a series of fine, very low growth wrinkles on its outer surface, parietal margin expanded beyond the middle level of the upper body whorl.

Description. Shell ( Figs. 15A–I , 29C ). Shell sinistral, medium-size for Hungerfordia species , very slender conical, last whorl widest when removing the expanded ribs and peristome. Shell color white, semi-transparent in fresh specimens, upper whorl occasionally colored faint yellow. Whorls 7.5–8, regularly coiled (increasing regularly in both width and height), convex or obtusely angulate at the periphery; last 1/8 whorls (just behind the aperture) expanded toward the aperture, ascending onto the penultimate whorl in left lateral view. Suture impressed. Constriction located above the parietal/columellar junction of the aperture, 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 2–2.5 whorls, smooth on apical whorl, weakly and finely punctuated near the suture on lower whorl. Apical septum absent. Axial ribs developed on the teleoconch, oblique to the coiling axis, strongly developed as tubular or folded spines on most whorls: ribs on the first 1/8 whorls of the teleoconch undeveloped; ribs on the following 1/4 whorls of the initial teleoconch low, closely spaced, not folded, gradually becoming more widely spaced; ribs on the subsequent whorls (except above the aperture) highly protruded as tubular or folded spines, strongly folded or curled at the periphery, very widely spaced (8–10 ribs in a whorl), not synchronized with those on the previous whorls, upper margin of the ribs above the tubular spines (between the suture and spines) low, indistinct; spiny projections on the ribs very high, weakly pointed, almost tubular or trough-shaped, opened at the tip, rather narrow, arising at some distance below the suture (near periphery of a whorl), folded almost vertically or curled, upper margin folded over or very close to the lower margin, protruded slightly upward on upper whorls, becoming to protruded rather downward on the last 3/4 whorls, 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 low and closely spaced, with greatly reduced spiny projections, 3–5, less folded than those on preceding whorls but retaining semi-circular edge at the periphery, hidden completely by parietal margin of the inner peristome. Interspace between the spiny ribs smooth, without axial sculpture. Spiral sculptures present throughout the teleoconch, fine, sinuous in high magnification, curved downward just above the spiny ribs, prominent below the periphery and on outer surface of spiny ribs. Base convex, without basal keel, with fine, short, very low growth wrinkles around the closed umbilicus. Axial protrusion of shell wall (along ribs) undeveloped on the last 3/4 whorls. Umbilicus closed in adult. Aperture slightly tilted downward against the coiling axis, strongly protruded; columellar axis within aperture almost vertical. Columellar tooth very weak, low, recessed within the aperture, located near the base of the columella. Peristome single; outer peristome undeveloped, but frequently with reduced spiny projections of axial ribs; inner peristome very widely expanded all around, circular, parietal margin expanded beyond middle level of the upper body whorl, outer surface with a series of fine, very low growth wrinkles.

Dimensions. Shell height 4.5–5.0 mm, diameter 2.8–3.6 mm, suture width 1.4–1.6 mm, peristome height 1.5– 2.0 mm.

Operculum ( Figs. 15J 1 –J 4 ). Operculum corneous, multispiral, circular, transparent, amber colored, thin, flat; outer surface smooth; inner surface with a low, thin, weak, arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula ( Fig. 9D ). Radula of specialized type of taenioglossate; ribbon very long. Central tooth very large, with a very wide, large, and blunt central cusp, with or without a pair of vestigial 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 a small inner cusp, without outer cusp, basal plate obliquely elongated. Inner marginal teeth shorter than the lateral teeth, elongated, with a large major cusp, with a slender inner cusp and a small outer cup. Outer marginal teeth with a large and blunt major cusp, with a slender inner cusp, without outer cusp.

Distribution and ecology. Endemic to Palau: Ngeruktabel and its satellite islets. The species inhabits vertical wall of large limestone rocks, occasionally on limestone rubbles.

Remarks. H. nudicollum is most similar to sympatric H. triplochilus , but differs from the latter by the absence of an outer peristome, the absence of lamellar ribs behind the aperture, the single inner peristome, the longer and wider spiny projections on the axial ribs, the more slender whorls, and the more widely expanded inner peristome at the parietal side.

Etymology. The specific name, derived from Latin nudus (= naked) and collum (= neck), refers to the absence of outer 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 15. Hungerfordia nudicollum sp. nov. (A1–A4) A paratype from Loc. Gk4-2, B0364a; (B) columellar tooth (dorsal view), a paratype from Loc. Gk4-2, B0364b; (C) axial ribs above the aperture, a subadult of topotypic paratype, B0146a; (D1) sculpture on the last 1–1.5 whorls, and (D2) sculpture on the last 1.5–2 whorls of a paratype from Loc. Gk4-2 (B0364a); (E) sculpture behind the aperture, a topotypic paratype, B0364c; (F) a paratype from Loc. Gk7-2, B0912; (G1–G4) holotype, B0364T; (H) a topotypic paratype, B0146b; (I) a paratype after removal of the spiny ribs, Loc. Gk4-2, B0364d; (J1, J2) outer surface, and (J3, J4) inner surface of operculum, a topotypic paratype, B0364. Scale bars, 1mm (A–I), 0.5 mm (J). 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.