Hungerfordia elegantissima 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 : 37-38

Hungerfordia elegantissima K. Yamazaki and Ueshima sp. nov.

( Figs. 9G , 11L , 18 , 29N )

Material examined. Holotype. An unnamed islet west of Ongael, northern side of Ngeruktabel island (Loc. Gk4- 3), Palau. Collected by R. U. and K. Y. on July 10, 2006. UMUTZ-MG-B0375 T . Paratypes: Ngeruktabel: Loc. Gk2-2, 13 specimens, 11/XI/2004, UMUTZ-MG-B0161; ditto, 4 specimens, 12/VII/2006, UMUTZ-MG-B0433; Loc. Gk4-4, 3 specimens, 11/VII/2006, UMUTZ-MG-B0386; Loc. Gk4-5, 8 specimens, 11/VII/2006, UMUTZ- MG-B0397; Loc. Gk4-6, 4 specimens, 11/VII/2006, UMUTZ-MG-B0410; Loc. Gk5-2, 2 specimens, 17/XI/2006, UMUTZ-MG-B0618; Loc. Gk7-2, 2 specimens, 27/I/2010, UMUTZ-MG-B0911; Loc. Gk7-3, 5 specimens, 29/I/ 2010, UMUTZ-MG-B0964; Loc. Gk7-6, 5 specimens, 30/I/2010, UMUTZ-MG-B1013; Loc. Gk8-4, 17 specimens, 2/III/2011, UMUTZ-MG-B1345; Loc. Gk8-6, 7 specimens, 2/III/2011, UMUTZ-MG-B1367. Ongael and other satellite islets of Ngeruktabel: Loc. Gk1-2, 7 specimens, 28/V/2003, UMUTZ-MG-B0036; ditto, 9 specimens, 10/XI/2004, UMUTZ-MG-B0144; ditto, 13 specimens, 10/VII/2006, UMUTZ-MG-B0345; Loc. Gk4- 2, 1 specimen, 10/VII/2006, UMUTZ-MG-B0362; Loc. Gk4-3, 46 specimens, 10/VII/2006, UMUTZ-MG-B0375; Loc. Gk7-1, 10 specimens, 27/I/2010, UMUTZ-MG-B0900; Loc. Gk7-1, 8 specimens, 27/I/2010, UMUTZ-MG- B0910; Loc. Gk8-3, 70 specimens, 26/II/2011, UMUTZ-MG-B1177 .

Diagnosis. Shell sinistral, small for Hungerfordia species , slender conical, wider than the height in fresh specimens due to the very long spiny ribs, last 1/16–1/8 whorls decoiled downwards and shortly separated from the previous whorl. Shell color white or yellow. Whorls weakly angulate at the periphery on the last 1.5 whorls. Constriction located a half whorl behind the aperture, not associated with prominent change of the spiny ribs. Axial rib highly protruded and strongly folded at the periphery as spines, widely spaced; lower margin of the ribs below the spines distinctly protruded at base of the last 1 to last 1/2 whorls; spiny projections of the ribs very long, narrow, strongly folded. Spiral sculptures fine. Umbilicus opened. Aperture strongly turned downward, opened almost horizontally, detached from the upper body whorl. Columellar tooth very weak and short. Peristome double: outer peristome expanded beyond the inner one, thin, with fine growth lines on the inner surface; inner peristome slightly protruded from the outer one. Interspace between the inner and outer peristome very narrow. Operculum thin, inner side with a strongly developed arcuate ridge which has a pair of lateral processes.

Description. Shell ( Figs. 11L 1 –L 2 , 18A–I , 29N ). Shell sinistral, small for Hungerfordia species , slender conical, last whorl widest when removing the spiny ribs, last 1/16–1/8 whorls decoiled downward. Shell diameter including the spiny ribs exceeds the shell height. Shell color white or light yellow. Whorls 5.5–6.5, convex on apical whorls, weakly angulate at the periphery on the last 1.5 whorls. Suture impressed. Constriction located a half whorl behind the aperture, not associated with prominent change of the spiny ribs, hardly recognizable in external view, internally without palatal plica except a low axial-crest caused by the constriction. Tuba only a half whorl. Protoconch 1+1/4 whorls, finely and very weakly punctated. Apical septum absent. Axial rib developed on the teleoconch, oblique to the coiling axis, strongly developed as spines on most whorls: ribs on the first 1/4 whorl of the teleoconch low, closely spaced, not folded; ribs on the subsequent whorls highly protruded at the periphery as spines, strongly folded at the periphery, widely spaced (14–15 ribs in a whorl); upper margin of the ribs above the spiny projections (between the suture and spines) low, indistinct or slightly elevated; lower (basal) margin of the ribs below the spines prominently protruded on the last 1 to last 1/2 whorls, becoming higher towards the umbilicus; spiny projections of the ribs very long, weakly pointed, slender, strongly folded at the periphery, depressed almost horizontally on the last 1.5 whorl, narrow, arising at some distance below the suture (near periphery of a whorl), decreased just below the periphery, protruded slightly upward on upper whorls, protruded horizontally or downward on the last whorl with a slight fluctuation around the constriction, upper margin folded over the lower margin, with fine spiral sculptures on the outer surface; ribs around the constriction almost unchanged, retaining a constant interval and similarly developed spiny projections as the preceding and following whorls, but basal margin of the axial ribs (below the spiny projections) becoming slightly lower after the constriction. Interspace between the spiny ribs almost smooth, without prominent axial sculpture except some faint growth lines on the last 1/2 whorls. Spiral sculptures present throughout the teleoconch, fine, weak, extended on the outer surface of the spiny ribs and outer peristome, sinuous in high magnification. Base slightly convex, without basal keel, with prominently protruded axial ribs which become higher toward the umbilicus. Umbilicus opened rather widely in adult, hidden by the decoiled inner peristome, visible in oblique umbilical view, width of c.a. 1/5 of shell diameter excluding the spiny ribs. Axial protrusion of shell wall (along the spiny ribs) undeveloped. Aperture strongly turned downward against the coiling axis, opened almost horizontally toward the base, strongly protruded downward, detached from the upper body whorl by the decoiling of the last 1/16–1/8 whorl. Columellar tooth reduced as a weak and very low swelling of columella, recessed inside the aperture, short. Peristome double, expanded: outer peristome expanded beyond the inner one at the palatal and basal sides, abruptly reduced at base of the columellar side to form a rounded baso-columellar edge, undeveloped on the parietal and upper columellar sides, thin, fragile, with fine and concentric growth lines on the inner surface; inner peristome squarish circular, thin, widely expanded at the parietal and columellar sides, slightly or hardly protruded from the outer one. Interspace between the inner and outer peristomes very narrow, almost smooth on the outer surface.

Dimensions. Shell height 3.0–3.9 mm, diameter 3.1–4.5 mm, suture width 1.4–1.8 mm.

Operculum ( Figs. 18J 1 –J 4 ). Operculum corneous, multispiral, circular, rather thin, transparent, amber colored, flat; outer surface smooth; inner surface with a strongly developed and modified arcuate ridge; arcuate ridge thick, almost right angled at both sides, highly protruded at lateral sides with a pair of thick processes directing towards the columella, low at central portion.

Penis. Penis absent.

Radula ( Fig. 9G ). 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, without inner nor outer cusp, basal plate obliquely elongated. Inner marginal teeth shorter, with a large major cusp, with two slender inner cusps and a small outer cup. Outer marginal teeth with a large and blunt major cusp, with two slender inner cusps, without outer cusp.

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

Remarks. H. elegantissima is easily distinguished from other spiny Hungerfordia species by the decoiling of the last 1/16–1/8 whorls, the aperture opened almost horizontally toward the base, the short tuba of only a half whorl, and the very long and slender spiny projections of the ribs, which never become shorter nor crowded around the constriction. H. elegantissima is also distinctive in having a unique operculum: the arcuate ridge on the inner surface has a pair of lateral processes.

Etymology. The specific name, derived from the superlative of Latin elegans, refers to the most beautifully sculptured shell among Hungerfordia species.

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 11. Variation of shell shape and sculpture within and among Palaina (Eupalaina) and Hungerfordia species. (A) P. (E.) moussoni Crosse, 1866, shell height 2.8 mm, B0272; (B) P. (E.) sp.-15, shell height 2.6 mm, B0090; (C) P. (E.) strigata Crosse, 1866, shell height 4.2 mm, B0205; (D) P. (E.) patula Crosse, 1866, shell height 4.9 mm, B0204; (E) P. (E.) wilsoni Crosse, 1866, shell height 3.2 mm, B0296; (F) H. polymorpha (Crosse, 1866), shell height 3.8 mm, B0049; (G) H. sp.- 23, shell height 1.3 mm, B0149; (H) H. sp.-13, shell height 5.1 mm, B0250; (I) H. triplochilus sp. nov., shell height 5.9 mm, B0158; (J) H. alata (Crosse, 1866), shell height 7.4 mm, B0058; (K1, K2) H. goniobasis goniobasis sp. et subsp. nov., shell height 3.1 mm, B0092; (L1, L2) H. elegantissima sp. nov., shell height 3.4 mm, B0375; (M) H. pelewensis Beddome, 1889, shell height 3.1 mm, B0651; (N1, N2) H. pelewensis Beddome, 1889, shell height 3.1 mm, B0046. Arrow heads show positions of the constriction. All specimens, UMUTZ-MG.

FIGURE 18. Hungerfordia elegantissima sp. nov. (A1–A4) A topotypic paratype, B0375a; (B) columellar tooth (oblique umbilical view), a paratype from Loc. Gk2-2, B0161; (C) columella (dorsal view), and (D) sculpture on the body whorl (front view) of topotypic paratypes (B0375a, b); (E) right lateral view of the last 1/2 whorl of a topotypic paratype showing the inner side of the constriction, B0375c; (F) a topotypic paratype after removal of the spiny ribs, B0375d; (G1–G6) holotype, B0375T; (H1, H2) a paratype from Loc. Gk7-2, B0911; (I) a topotypic paratype, B0375e; (J1, J2) outer surface, and (J3, J4) inner surface of operculum, a paratype from Loc. Gk2-2, B0161. Scale bars, 1mm (A–I), 0.5 mm (J). Arrow heads show positions of the constriction. 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 2–3. Enlarged maps of Palau islands showing collecting sites. Top (Fig. 2), map of southern part of Babeldaob island; bottom (Fig. 3), map of Koror island and its neighboring islands or islets. Abbreviations of the collecting sites are listed in Table 2.

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.