Hungerfordia subalata 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 : 49-52

Hungerfordia subalata K. Yamazaki and Ueshima sp. nov.

( Figs. 9K , 23 , 29I )

Hungerfordia A in part: Rundell, 2010, pp. 86, 88, Table 2.

Materials examined. Holotype. South of Ongeulklbub , north-east of Ngeruktabel island (Loc. Gk4-4), Palau. Collected by R. U. and K. Y. on July 11, 2006. UMUTZ-MG-B0385 T . Paratypes. Ngeruktabel: Loc. Gk1-1, 9 specimens, 26/V/2003, UMUTZ-MG-B0021; Loc. Gk1-1, 48 specimens, 12/VII/2006, UMUTZ-MG-B0425; Loc. Gk4-4, 37 specimens, 11/VII/2006, UMUTZ-MG-B0385; ditto, 1 specimen, 18/XI/2006, UMUTZ-MG-B0637; Loc. Gk4-5, 8 specimens, 11/VII/2006, UMUTZ-MG-B0399; Loc. Gk5-4, 17 specimens, 18/XI/2006, UMUTZ- MG-B0646; ditto, 26 specimens, 27/X/2007, UMUTZ-MG-B0888; Loc. Gk5-5, 5 specimens, 18/XI/2006, UMUTZ-MG-B0655; ditto, 3 specimens, 22/X/2007, UMUTZ-MG-B0726; Loc. Gk6-2, 38 specimens, 22/X/2007, UMUTZ-MG-B0738; Loc. Gk6-4, 27 specimens, 27/X/2007, UMUTZ-MG-B0881; Loc. Gk7-5, 38 specimens, 30/ I/2010, UMUTZ-MG-B0999; Loc. Gk7-6, 31 specimens, 30/I/2010, UMUTZ-MG-B1011; Loc. Gk7-7, 4 specimens, 30/I/2010, UMUTZ-MG-B1028; Loc. Gk7-8, 15 specimens, 30/I/2010, UMUTZ-MG-B1037; Loc. Gk8-4, 48 specimens, 2/III/2011, UMUTZ-MG-B1347; Loc. Gk8-7, 48 specimens, 2/III/2011, UMUTZ-MG- B1379. Satellite islets of Ngeruktabel: Loc. Gk7-4, 4 specimens, 29/I/2010, UMUTZ-MG-B0973; Loc. Gk8-2, 45 specimens, 25/II/2011, UMUTZ-MG-B1140 .

Diagnosis. Shell sinistral, very large for Hungerfordia species , slender conical. Shell color white or yellowish white. Constriction located above the aperture, frequently associated with reduction of the wing-like ribs. Apical septum absent. Axial ribs on most whorls highly protruded as wings, very widely spaced, folded at the periphery; wing-like projections of the ribs very high, wide, arising at the suture on upper whorls; ribs above the aperture closely spaced or not, with slightly to greatly reduced wing-like projections. Interspace between the wing-like ribs with characteristic growth wrinkles; lower growth wrinkles developed above the suture of the last 1.25–3 whorls, very short, closely spaced, lamellar, white. Spiral sculptures fine. Umbilicus closed or narrowly open. Aperture evidently (but weakly) tilted downward against the coiling axis. Columellar tooth reduced or very weakly developed deeply inside the aperture. Peristome double, widely expanded; outer peristome very widely expanded beyond the inner one, with a rounded baso-columellar edge; inner peristome squarish circular, parietal margin located far below the middle level of the upper body whorl. Interspace between the inner and outer peristomes narrow.

Description. Shell ( Figs. 23A–I , 29I 1 –I 2 ). Shell sinistral, very large for Hungerfordia species , slender conical, last whorl widest when removing the protruded ribs and peristomes. Shell color white or yellowish white, upper whorls occasionally yellow or reddish brown with the color becoming deeper towards the apex. Whorls 6–7, convex; last 1/16–1/8 whorls (including interspace between the outer and inner peristomes) expanded upward, weakly or prominently ascending onto the penultimate whorl in left lateral view. Suture impressed. Constriction located above the parietal/columellar junction of the aperture, associated with reduction of wing-like ribs to some extent, internally without palatal plica except a low axial-crest caused by the constriction. Tuba 7/8 whorls. Protoconch 1+1/4 to 1.5 whorls, almost smooth, lower whorl faintly and very finely punctated below the suture. Apical septum absent. Axial ribs developed on the teleoconch, oblique to the coiling axis, strongly developed as wings on most whorls; ribs undeveloped on the first 1/4 whorls of the teleoconch; ribs on the subsequent 1/4–1/2 whorls of the initial teleoconch, low, moderately or rather widely spaced, not folded; ribs on the subsequent whorls (except above the aperture) highly and widely protruded as wings, very widely spaced (7–10 ribs in a whorl), not synchronized with those on the previous whorls, folded at the periphery; upper margin of the ribs above the winglike projection (between the suture and wing) on the last 2 whorls low, indistinct or slightly elevated; wing-like projections of the ribs very high, wide, weakly pointed, weakly curved upward, arising at the suture on upper whorls, becoming to arising at some distance below the suture on the last 2–3 whorls, upper margin slightly folded at the periphery over the lower margin, lower margin widely expanded below to suture of the next whorl, protruded rather upward on most whorls, becoming protruded laterally to rather downward on the last 1/3 whorls, 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) rather closely spaced, with greatly or slightly reduced wing-like projections (but always retaining at least low wing-like projections), becoming less folded at the periphery towards the constriction. Interspace between the wing-like ribs with characteristic growth wrinkles: lower growth wrinkles developed above the suture of the last 1.25–3 whorls, distinctive, very short, lamellar, regularly spaced, white; upper growth wrinkles developed below the suture on the last 2–3 whorls, fine, low, becoming crowded behind the wing-like ribs. Spiral sculptures present on the teleoconch, fine, weak, extending on outer surface of the wing-like ribs and outer peristome, sinuous in high magnification. Base convex, without basal keel, with some fine and low growth wrinkles around the umbilicus. Umbilicus closed or narrowly open in adult. Axial protrusions of shell wall (along the wing-like ribs) developed on the last 3/4 whorls; abapertural side narrower; adapertural side wide and convex in umbilical view. Aperture weakly tilted downward against the coiling axis, slightly or hardly protruded; columellar axis within aperture slightly oblique against the coiling axis. Columellar tooth mostly reduced, very weakly developed in some populations, recessed deeply inside the aperture, very low when present. Peristome double, widely expanded; outer peristome very widely expanded beyond the inner one at the palatal and basal sides, abruptly reduced at the lower columellar side to form a rounded baso-columellar edge, undeveloped at all at the upper columellar side, weakly reflected backward, smooth and polished on the inner surface, with fine spiral sculptures on the outer surface; inner peristome squarish circular, expanded outward all around but less expanded at the parietal side, not so thick, hardly reflected backward, parietal margin located far below the middle level of the upper body whorl, strongly protruded from the outer one at the columellar side but less protruded at the palatal and basal sides. Interspace between the inner and outer peristomes narrow; uppermost margin prominently or very weakly ascending onto the penultimate whorl toward the aperture in left lateral view.

Dimensions. Shell height 5.0–7.5 mm, diameter 3.7–6.0 mm, suture width 2.2–3.0 mm, peristome height 1.6– 2.9 mm.

Operculum ( Figs. 23J 1 –J 4 ). Operculum corneous, multispiral, circular, thin, transparent, amber colored, slightly concave; outer surface smooth; inner surface with a low, thin, weak, arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula ( Fig. 9K ). Radula of specialized type of taenioglossate; ribbon very long. Central tooth very large, with a very wide 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 than the lateral teeth, with a large and wide major cusp, with two slender inner cusps, with 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: Ngeruktabel island and its satellite islets. The species inhabits vertical walls of large limestone rocks or cliffs, occasionally on limestone rubbles.

Variations. H. subalata shows some local variations. Typical morph collected from central part of Ngeruktabel island has an closed umbilicus, and the ribs above the aperture are closely spaced and with very low wing-like projections ( Figs. 23A–F ). Whereas, some specimens collected from northern part of the island have a narrowly opened umbilicus, and the ribs above the aperture are widely spaced and with developed wing-like projections ( Figs. 23G 1 –G 3 ). Although these two morphs seem substantially different, they are linked by a series of intermediates ( Fig. 23H ). Morphology of the umbilicus and reduced ribs above the aperture are not necessarily concordant in some populations, and density of the reduced ribs above the aperture varies even within a population. In addition, all these morphs share diagnostic features of the species, such as the absence of an apical septum, the presence of lower growth wrinkles above the suture, the narrow interspace between the inner and outer peristome, and the basally located aperture. Therefore, we regard these morphs as intraspecific variation within H. subalata .

Remarks. H. subalata is most similar to H. alata , but differs by the absence of an apical septum, the presence of characteristic lower growth wrinkles above the suture between the wing-like ribs, the aperture being tilted downward, the parietal margin of the inner peristome being located far below the middle level of the upper body whorl, and the narrower interspace between the inner and outer peristomes. Additionally, in H. subalata , both the outer and inner peristomes are less expanded, and the inner peristome is not so thickened nor reflected as H. alata .

Etymology. The specific name, derived from Latin sub and alata , refers to the shell similarity to H. alata .

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 23. Hungerfordia subalata sp. nov. (A1–A4) A topotypic paratype, B0385a; (B) columellar tooth (dorsal view), (C) axial ribs above the aperture, and (D) sculpture on the penultimate whorl of topotypic paratypes (B0385a, b); (E) sculpture above the suture of the last whorl, holotype, B0385T; (F1–F4) holotype, B0385T; (G1–G3) a paratype from Loc. Gk6-2, untypical morph with developed spiny ribs above the aperture and with a narrowly opened umbilicus, B0738; (H) a paratype from Loc. Gk5-5, B0655; (I) a paratype from Loc. Gk4-4, B0425; (J1, J2) outer surface, and (J3, J4) inner surface of operculum, a topotypic paratype, B0385c. 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 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.