Gyliotrachela torticollis Benthem Jutting, 1962

Sutcharit, Chirasak, Ngor, Peng Bun, Páll-Gergely, Barna, Jeratthitikul, Ekgachai, Siriwut, Warut, Srisonchai, Ruttapon, Ng, Ting Hui, Jirapatrasilp, Parin & Panha, Somsak, 2023, Notes on the hypselostomatid snails (Gastropoda: Heterobranchia) from limestone hills in Western Cambodia with a new record and a new species, Journal of Natural History 57 (25 - 28), pp. 1287-1303 : 1287-1303

Gyliotrachela torticollis Benthem Jutting, 1962

( Figures 1 , 3 ; Table 1 )

Gyliotrachela torticollis Benthem Jutting, 1962: 8–10 , fig. 4. Type locality: Phum Troung Mean , 15 km south-west of Battambang, Cambodia [Phnom Troung Mean] .

Material examined

CAMBODIA: Paratype RMNH-ZMA 137136 (3 shells; Figure 3 (a)) from Phuom Troung Mean , 15 km SW of Battambang . CUMZ 14204 (33 shells; Figure 3 (b, c)) from Phnom Sampeov Mountain, Banan District , Battambang Province (13.026000°N, 103.101011°E) . CUMZ 14205 (113 shells) from Cave at Phnom Banan Temple, Banan District , Battambang Province (12.951464°N, 103.143903°E) .

Diagnosis

Shell depressed heliciform, and long and descending tuba. Protoconch sculptured with only shallow pits; teleoconch with spiral striation. Apertural dentition with five major lamellae (parietal, angular, upper and lower palatals, basal, and columellar), and numerous plicae. All lamellae and plicae spinose.

Description

Shell depressed heliciform, last whorl enlarged with descending tuba, and spire elevated and conical. Shell colour brownish, 3.0– 3.2 mm in length, 3.1–3.3 mm in width, and with 4–4½ whorls. Protoconch about two whorls and sculptured with roundish and shallow pits. Teleoconch with irregularly strong or weak growth lines, and malleations or wrinkles arranged on thin spiral striations. Spire raised, whorl rounded and evenly sloped, and impressed suture. Last whorl shouldered, little concaved periphery, and long tuba projecting anteriorly downward. Two wide and shallow furrows present, one on upper periphery, and one surrounding umbilicus and extended to expanded lip. Aperture irregularly circular; peristome free with broadly expanded lip margins. Apertural dentition with five prominent lamellae: parietal, angular, upper and lower palatals, and columellar. Parietal (p) and angular (a) lamellae very close together; parietal tall; angular shorter than parietal and situated anteriorly to peristome. Palatal wall with strong upper (upl) and lower palatal (lpl) lamellae, three small suprapalatal plicae, one or two interpalatal plicae, and one small and one tiny infrapalatal plicae. Columella area with strong columellar (c) lamella, two tiny subcolumellar plicae, and three small supracolumellar plicae. All apertural dentition (lamellae and plicae) with small spines along approximately central line of lamellae. Umbilicus very wide and showing nearly all preceding whorls.

Distribution

It is known from multiple limestone outcrops in Battambang Province, Cambodia ( Figure 1 ). The collection locality in Phnom Sampeov is about 1.8 km east of the Phnom Troung Mean, the original type locality of this species ( Benthem Jutting 1962). Snails live on the limestone wall, in rock crevices, and near the cave entrance.

Differential diagnosis

Gyliotrachela torticollis is superficially similar to H. srakeoensis , but it differs by having thin spiral striations on the last whorl and angular lamella present, while H. srakeoensis has only a wrinkled shell surface without spiral striations, and angular lamella is absent. This species differs from A. chaunosalpinx from southern Cambodia in having a depressed heliciform shell, lower conical spire, descending tuba, distinctly shouldered last whorl, angular lamella present, and no hook-shaped lamella in the aperture. In comparison, A. chaunosalpinx possesses a turreted heliciform shell, elevated spire, little descending tuba, angular last whorl, without angular lamella, and with hook-shaped lamella in the aperture ( Vermeulen et al. 2019b).

Remark

This species is probably endemic to Battambang Province, Cambodia.

Figures

Figure 1. Distribution map of all hypselostomatids known from Cambodia. The small black dots indicate the approximate type locality for 1. Acinolaemus carcharodon, 2. Acinolaemus pyramidalis, 3. Acinolaemus rectus, 4. Anauchen chaunosalpinx, 5. Anauchen depressus, 6. Aulacospira conica, 7. Aulacospira furtiva, 8. Gyliotrachela khmeriana sp. nov., 9. Gyliotrachela torticollis, 10. Hypselostoma benetuitum, 11. Hypselostoma cambodjense, 12. Hypselostoma discobasis, and 13. Hypselostoma srakeoensis. The approximate location of limestone areas in Cambodia (Sisophon-Battambang, Stung Treng, and Kampot areas) is modified from Mouret (2004). Asterisks (*) indicate new localities recorded in this study.

Figure 3. Gyliotrachela torticollis. (a) Paratype ZMA 137136 from Phuom Troung Mean,Cambodia,with apertural dentition. (b, c) Specimen CUMZ 14204 from Phnom Sampov, Battambang, (b) shell with apertural dentition arrangement with its surface sculpture, and (c) protoconch sculpture. Abbreviations: a = angular lamella, b = basal lamella, c = columellar lamella, lpl = lower palatal lamella, p = parietal lamella, upl = upper palatal lamella.