Hungerfordia triplochilus 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 : 24-27

Hungerfordia triplochilus K.Yamazaki and Ueshima sp. nov.

( Figs. 6C 3 , 9B , 11I , 13 , 29A )

Material examined. Holotype. “Milky way”, southern coast of central part of Ngeruktabel island (Loc. Gk2-2), Palau. Collected by R. U. and K. Y. on Nov. 11, 2004. UMUTZ-MG-B0158 T . Paratypes. Koror: Loc. Ko 2-2, 16 specimens, 7/XI/2004, UMUTZ-MG-B0060 . Ulebsechel: Loc. Ub 7-1, 1 dead specimen, 31/I/2010, UMUTZ-MG- B1050 . Ngeruktabel: Loc. Gk 1-1, 3 specimens, 26/V/2003, UMUTZ-MG-B1447; ditto, 16 specimens, 12/VII/ 2006, UMUTZ-MG-B0424; Loc. Gk2-2, 23 specimens, 11/XI/2004, UMUTZ-MG-B0158; ditto, 9 specimens, 12/ VII/2006, UMUTZ-MG-B0436; Loc. Gk4-5, 10 specimens, 11/VII/2006, UMUTZ-MG-B0396; Loc. Gk4-6, 4 specimens, 11/VII/2006, UMUTZ-MG-B0411; Loc. Gk5-2, 9 specimens, 17/XI/2006, UMUTZ-MG-B0619; Loc. Gk6-2, 1 specimen, 22/X/2007, UMUTZ-MG-B0745; Loc. Gk6-4, 14 specimens, 27/X/2007, UMUTZ-MG- B0882; Loc. Gk7-2, 4 specimens, 27/I/2010, UMUTZ-MG-B0913; Loc. Gk7-3, 4 specimens, 29/I/2010, UMUTZ- MG-B0957; Loc. Gk7-5, 1 specimen, 30/I/2010, UMUTZ-MG-B1000; Loc. Gk7-6, 8 specimens, 30/I/2010, UMUTZ-MG-B1009; Loc. Gk7-7, 1 specimen, 30/I/2010, UMUTZ-MG-B1025; Loc. Gk7-8, 2 specimens, 30/I/ 2010, UMUTZ-MG-B1038; Loc. Gk8-4, 19 specimens, 2/III/2011, UMUTZ-MG-B1346; Loc. Gk8-7, 30 specimens, 2/III/2011, UMUTZ-MG-B1378. Ongael and other satellite islets of Ngeruktabel: Loc. Gk 1-2, 38 specimens, 10/XI/2004, UMUTZ-MG-B0145; ditto, 5 specimens, 28/ V /2003, UMUTZ-MG-B0031; ditto, 9 specimens, 10/VII/2006, UMUTZ-MG-B0346; Loc. Gk4-2, 13 specimens, 10/VII/2006, UMUTZ-MG-B0363; Loc. Gk 4-3, 38 specimens, 10/VII/2006, UMUTZ-MG-B0376; Loc. Gk 7-4, 1 specimen, 29/I/2010, UMUTZ-MG- B0974 .

Diagnosis. Shell sinistral, large for Hungerfordia species , slender conical. Shell color white. Constriction located above the aperture, associated with abrupt reduction of the spiny ribs. Apical septum occasionally present. Axial rib on most whorls highly protruded as spines, widely spaced, strongly folded at the periphery; 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; ribs above the aperture closely spaced, low, with greatly reduced spiny projections. Interspace between the spiny ribs with growth wrinkles; growth wrinkles developed below the suture on the last 3–4 whorls, very low, fine, rather long. Spiral sculptures fine. Aperture weakly protruded, hardly tilted. Columellar tooth very weak. Peristome triple, widely expanded: outer peristome expanded beyond the inner one, with a rounded baso-columellar edge; inner peristome double, with a distal inner peristome just behind the proximal one, parietal margin located near the middle level of the upper body whorl. Interspace between the outer and inner peristomes wide, with a series of lamellar ribs on the outer surface.

Description. Shell ( Figs. 6C 3 , 11I , 13A–I , 29A ). Shell sinistral, large for Hungerfordia species , slender conical, last whorl widest when removing the expanded ribs and peristomes. Shell color white, upper whorls occasionally faint yellow. Whorls 7–7.5, regularly coiled (increasing regularly in both width and height), slightly convex, sides above the periphery almost flat, very weakly angulate at the periphery; 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 inner peristome, associated with abrupt reduction of the spiny ribs, internally without palatal plica except a low axialcrest caused by the constriction. Tuba 7/8 whorls. Protoconch 1–1.5 whorls, almost smooth, very weakly and finely punctated. Apical septum present or absent, constructed at 0–7/8 whorls after the protoconch/teleoconch junction when present. Axial ribs developed on the teleoconch, oblique to the coiling axis, strongly protruded as spines on most whorls: ribs hardly developed on the first 1/8 of the teleoconch; ribs on the following initial 1/8–1/4 whorls low, closely spaced, not folded; ribs on the subsequent whorls (except above the aperture) highly protruded as spines, widely spaced (11–13 ribs in a whorl), not synchronized with those on the previous whorls, folded at the periphery; upper margin of the ribs above the spiny projections (between the suture and spines) low, indistinct; spiny projections of the ribs very high, weakly pointed, folded at the periphery, trough-shaped, rather narrow, arising at some distance below the suture (arising near periphery of a whorl), upper margin folded over the lower margin, lower margin weakly extended below to the suture of the next whorl, with fine spiral sculptures on the outer surface, protruded laterally on most whorls, becoming protruded rather downward on the last 5/8 whorls; ribs above the aperture (ribs on the last 1 to last 3/4 whorls around the constriction) abruptly becoming low and closely spaced, with greatly reduced spiny projections (but still retaining very low spiny projections), less folded at the periphery than those on the preceding whorl, almost hidden by the expanded inner peristome. Interspace between the spiny ribs with characteristic growth wrinkles; growth wrinkles developed below the suture on the last 2–4 whorls, very low, fine, rather long (but never exceed beyond the periphery). Spiral sculptures present throughout the teleoconch, fine, rather prominent below the periphery, sinuous in high magnification, extending on the outer surface of the spiny ribs and outer peristome. Base convex, with some short, low growth wrinkles around the closed umbilicus, without basal keel. Axial protrusions of shell wall (along the ribs) hardly developed on the last whorl. Umbilicus closed in adult. Aperture hardly tilted against the coiling axis, weakly protruded from the previous whorl; columellar axis within the aperture almost vertical. Columellar tooth present, weak, recessed deeply inside the aperture. Peristome triple, with an outer peristome and doubled inner peristomes, widely expanded; outer peristome thin, expanded beyond the inner one at the palatal and basal sides, with a rounded basocolumellar edge, weakly reflected backward, smooth and polished on the inner surface, with fine spiral sculptures on the outer surface; inner peristome strongly protruded from the outer one, double with distal and proximal inner peristomes; distal inner peristome usually developed just behind the proximal one, hardly or slightly expand beyond the proximal one; proximal inner peristome circular or squarish circular, widely expanded outward in all around, parietal margin located near the middle level of the previous whorl. Interspace between the outer and inner peristomes wide, with a series of closely spaced, lamellar ribs on the outer surface; uppermost margin ascending onto the penultimate whorl toward the aperture in left lateral view; base extended almost horizontally in left lateral view.

Dimensions. Shell height 5.4–6.4 mm, diameter 3.3–4.6 mm, suture width 1.9–2.5 mm, peristome height 1.8– 2.6 mm.

Operculum ( Figs. 13J 1 –J 4 ). Operculum corneous, multispiral, circular, transparent, amber colored, thin, flat; outer surface smooth; inner surface with a low, thin, arcuate ridge near the columellar margin.

Penis. Penis absent.

Radula ( Fig. 9B ). 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 one or two vestigial inner cusps, without outer cusp, basal plate obliquely elongated. Inner marginal teeth shorter than the lateral teeth, with a large major cusp, with a slender inner cusp and a small outer cup. Outer marginal teeth with a large, wide and blunt major cusp, with a slender inner cusp, without outer cusp.

Distribution and ecology. Endemic to Palau: Type specimens were collected from Koror (eastern limestone area), Ulebsechel, and Ngeruktabel islands and the satellite islets (see remarks below). This species is frequently found underside of limestone rocks.

Remarks. H. triplochilus is distinguished from other spiny Hungerfordia species by the doubled inner peristomes, the wide interspace between the inner and outer peristomes, which has a series of lamellar ribs on its outer surface, and the narrower spiny projections of the ribs, which arise some distance below the suture. H. triplochilus is most similar to H. nudicollum , but differs from the latter by the presence of an outer peristome, development of the distal inner peristome, the presence of lamellar ribs behind the inner peristome, the less expanded inner peristome, the larger and broader shell, the more closely spaced ribs, the shorter spiny projections on the ribs, and having larger numbers of reduced ribs above the aperture.

There are some problematic taxa that resemble to H. triplochilus . These taxa, which might be closely related species or local variants of H. triplochilus , were not included in this study. Morphological variation and distribution of H. triplochilus will be discussed in detail after a critical revision on these problematic taxa.

Etymology. The specific name, derived from Greek triplos (= triple) and cheilos (= lip), refers to the tripled peristomes (having an outer peristome and doubled inner peristomes).

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 6. Terminology used in this study. (A) Shell dimensions. Abbreviations: D, shell diameter; H, shell height; PH, peristome height; SW, suture width. (B) An example showing the axial protrusions of shell wall along the axial ribs. Umbilical view of a shell of Hungerfordia pyramis (Crosse, 1866), only the last whorl shown. (C) Apical septa of some Hungerfordia species: (C1) apical whorls of a shell (live condition) of H. pteropurpuroides sp. nov.; (C2) apical whorls of a partially opened shell of H. alata (Crosse, 1866), which shows construction of an internal septum; (C3) subapical view of a shell of H. triplochilus sp. nov. after removal of the empty apical whorls above the septum.

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 13. Hungerfordia triplochilus sp. nov. (A1–A5) A topotypic paratype, B0158a; (B) columellar tooth (left lateral view), topotypic paratype, B0158b; (C) axial ribs above the aperture, a subadult of topotypic paratype, B0158c; (D1) sculpture on the last 1–1.5 whorls, and (D2) sculpture on the last 1.5–2 whorls of topotypic paratypes (B0158a, d); (E1–E4) holotype, B0158T; (F) apical septum, a partially opened paratype from Loc. Gk1-2, B0145; (G) sculpture behind the aperture, holotype, B0158T; (H) a worn paratype from Loc. Gk7-7, B1025; (I) a paratype from Loc. Gk7-5, B1000; (J1, J2) outer surface, and (J3, J4) inner surface of operculum, a topotypic paratype, B0158. Scale bars, 1mm (A–E, G–I), 0.5 mm (F, 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.