Sinoennea houaphanica Inkhavilay, Inthavong and Oulaiseng, 2024

Inkhavilay, Khamla, Vanhdibay, Anny, Inthavong, Arpatsa, Oulaiseng, Chantha, Phommachan, Vongsadeth, Tongkerd, Piyoros, Jeratthitikul, Ekgachai, Panha, Somsak & Sutcharit, Chirasak, 2024, Two new species of the carnivorous snail genus Sinoennea Kobelt, 1904 (Eupulmonata: Diapheridae) from Laos, Journal of Natural History 58 (45 - 48), pp. 2017-2031 : 2024-2028

Sinoennea houaphanica Inkhavilay, Inthavong and Oulaiseng sp. n.

( Figures 3, 4 (d))

http://www.zoobank.org/urn:lsid:zoobank.org:act:722F2394-9862-409E-8429-

E0ACCB0B1734

Type material

Holotype CUMZ 14209 (height 5.7 mm, width 3.0 mm, 8½ whorls; Figures 3 (a), and 4(d) coll. K. Inkhavilay, A. Inthavong, and C. Oulaiseng. Paratypes CUMZ 14210 (1 shell; Figure 3 (b,c)) and NHMUK (1 shell) all with the same collecting data as the holotype.

Type locality

The limestone outcrop at Ban Lao, Xamtay District, Houaphanh Province, Laos (20.014556° N, 104.682500°E) .

Etymology

The species name ‘ houaphanica ’ is derived from the type locality, Houaphanh Province, where the type specimens were collected; the Latin suffix ‘- ica ’ means ‘belonging to’ .

Diagnosis

Ovate cylindrical, glossy, and ribbed shell; rounded aperture; parietal callus not elevated; apertural dentition with three folds (parietal, lower palatal, and columella); umbilicus narrow with swelling on inner part of last whorl.

Description ( Figure 3)

Shell ovate-cylindrical, somewhat translucent, and pale yellow to light white. Shell height 5.3–5.7 mm, shell width 2.7–3.0 mm, and with 7–8½ whorls. Protoconch approximately two whorls and nearly smooth and glossy, or with very fine radial ribs. Teleoconch glossy overall with strong and regularly spaced radial ribs, slightly weaker on last whorls behind aperture. Individual ribs with blunt ridges on earlier whorls, and becoming curved ridges on penultimate and last whorls. Whorls moderately bulging; suture wide and impressed. Aperture subovate to somewhat rounded; peristome thickened, expanded, and slightly reflected. Parietal callus thickened, not elevated, and reaching approximately half of preceding whorl. Apertural dentition with three conspicuous folds and slight indication of very low basal plica. Parietal lamella (p) well-developed, enlarged, and strong; outer portion thickened, strongly bent in direction of columella; inner part lower and thinner. Sinulus relatively wide, elongated ovate, and well isolated. Lower palatal plica (lpl) thickened, strong, and located inside aperture. Columellar lamella (c) situated very deeply, plate-like, long, sharp, vertical, and nearly parallel to columellar axis. Umbilicus narrowly opened, deep, and strong periumbilical keel; inner part of last whorl with swelling near peristome.

Distribution

Sinoennea houaphanica sp. n. is known only from the type locality in Houaphanh Province, Laos ( Figure 1 (a)) . Snails were found in the leaf litter in limestone-rock crevices.

Differential diagnosis

This new species can be distinguished from S. infantilis and S. variabilis by its larger shell (height> 5.3 mm; Table 1), ovate aperture, palatal plica, and very large and robust columellar lamella situated deeply inside the aperture. In contrast, the latter two species ( Figure 4 (g,h)) tend to have smaller shells (height <2 mm; Table 1), triangular apertures, two palatal plicae, and a small columellar lamella situated close to the apertural lip Páll-Gergely, Reischütz et al. (2020).

When compared to closely related species, S. houaphanica sp. n. can be distinguished from S. euryomphala Inkhavilay and Panha in Inkhavilay et al. 2016 from Laos by its ovate shell, rounded aperture, three prominent apertural dentitions, aperture adnate to the preceding whorl, sinulus ovate and slightly wide, lack of outer palatal plica, narrow umbilicus (without periumbilical groove), and swelling on the inner part of the last whorl. Sinoennea euryomphala ( Figure 4 (c)) possesses an elongate-ovate shell, narrowly ovate aperture, sinulus curved and very narrow, connected upper and lower palatal plicae, widely opened umbilicus (with a periumbilical groove), and swelling on the inner part of the last whorl absent ( Inkhavilay et al. 2016).

In comparison with two other potentially similar species, S. prima Panha and Burch, 2002 from Thailand and S. lizae Maassen, 2008 from Laos, S. houaphanica sp. n. has an ovate shell, a rounded aperture, and one palatal plica, whereas S. prima and S. lizae ( Figure 4 (e)) have elongated cylindrical shells, ovate apertures, and two separate palatal plicae ( Panha and Burch 2002; Maassen 2008).

In addition, S. houaphanica sp. n. differs from S. macrodonta ( Bavay and Dautzenberg, 1912) from Vietnam in having a larger shell (height> 5.3 mm; Table 1), strong and prominent radial ribs, no elevated parietal callus, one palatal plica, and one large columellar lamella situated inside the aperture. In comparison, S. macrodonta ( Figure 4 (l)) possesses a smaller shell (height <3 mm), less prominent radial ribs, elevated parietal callus, two separated palatal plicae, and two columellar lamellae (one knob-like near the apertural lip and one large, situated more deeply in the aperture) ( Bavay and Dautzenberg 1912).

This new species looks similar to S. strophiodes ( Gredler, 1881) from Hunan, China, and S. menglunensis Wang, Chen, Zhou and Hwang, 2015 from Yunnan, China, in having ovate cylindrical shell form. However, the main distinctions are only lower palatal lamella present and closely placed radial ribs in S. houaphanica sp. n. These two Chinese species possess two palatal lamellae (upper and lower lamellae) and widely spaced radial ribs. Furthermore, S. strophiodes ( Figure 4 (n)) has a narrow-expanded lip, and S. menglunensis ( Figure 4 (m)) has the last three whorls equal in width ( Wang et al. 2015; Páll-Gergely, Hunyadi et al. 2020).

Remarks

Although only a few shells are known, this species is quite stable in its shell characteristics. The type series was collected under damp soil with leaf litter from rock outcrops in vegetated limestone areas.