Pincerna yanseni Páll-Gergely, 2017

Páll-Gergely, Barna, 2017, A new species of Alycaeidae, Pincerna yanseni n. sp. from Sumatra, with the resurrection of the genus Pincerna Preston, 1907 (Gastropoda: Cyclophoroidea), Raffles Bulletin of Zoology 65, pp. 213-219 : 214-219

Pincerna yanseni Páll-Gergely n. sp.

Figs. 1B , 2 A–F, 3A–E, 4.

Type material. Holotype (1 shell: MZB.Gst. 18.970), Indonesia, Sumatera Barat (West Sumatra), Solok Selatan (South Solok Regency), Koto Parik Gadang Diateh subdistric, Goa [=cave] Pinti kayu, Near Sungai [=river] Dareh , approximate GPS position: 1.3027°S, 101.1164°E, found in soil sample collected by local people, 26 February – 2 March 2015.

Paratypes: HNHM 99999 /1 , NHMUK 201700137 /1, SMF 349027/1 , PGB/2 , YSC/15 , Same data as holotype ; WM/11 , IND.38, West Sumatra, Baso, 14 km NW of Bukittinggi in direction Payakumbuh , overgrown limestone outcrop along road, approx. GPS coordinates: 0°16.6′S, 100°29′E, coll. Maassen, W.J.M, July 1996 ; WM/1 , IND.42 West Sumatra, near entrance of Cave Gua Pangian, 3 km N of village Lintau , SE of Bukittinggi, 0°28′′19.5″S, 100°45′11.7″E, coll. Maassen, W.J.M, July 1996 ; WM/3 , Same locality, coll. Maassen, W.J.M, July 1997; IND.66 West Sumatra, Kampung Desa Gadut , limestone rocks near the village, E of Payakumbuh, 0°15′36.0″S, 100°43′58.7″E, leg. Maassen W.J.M, July 1997 , WM / 3 paratypes ; WM/3 , IND.67 West Sumatra, Kampung Desa Gadut , limestone rocks half hour walk from village, E of Payakumbuh, 0°15′35.1″S, 100°44′01.1″E, coll. Maassen, W.J.M, July 1997; WM/1 (live collected specimen), IND.35 West Sumatra, Bungus Bay, 25 km SE of Padang, 2 km N of village near waterfall, coll. Maassen, W.J.M, July 1997; PGB/5 , WM/33 + 3 figured shells, ZRC.MOL.9410/2, IND.65 West Sumatra, at cave near Sitimbuk , 30 km E of Bukittinggi , 0°21′05.6″S, 100°34′10.1″E, coll. Maassen, W.J.M, July 1996.

Etymology. This new species is dedicated to Yansen Chen (Medan, Indonesia), who first called my attention to this species and provided shell material.

Description. ( Figs. 1B , 2 A–F): Shell conical ovoid, translucent; 3.5–3.75 rounded whorls, suture deep; protoconch slightly more than 1.5 whorls; protoconch glossy, lacking prominent sculptural features ( Fig. 2A ); first 1.75 whorls of R1 with low, relatively dense, regular ribs and weaker, dense spiral striation; this sculpture gradually changes to a more sparsely ribbed region, which spans approximately half a whorl; R2 and tube very short, with 8–9 ribs that are very slender and only slightly elevated from the surface; R2 ribs lighter in colour than rest of shell; anterior crust thin, nearly horizontal, without an elevated rib, forming a tunnel with the more robust posterior crust ( Figs. 2 B–F); R3 with fine, regular spiral, and irregular radial lines, the spiral ones are dominant; aperture rounded; outer peristome widened, sharp, expanded, but not reflexed, and does not cover the umbilicus as in most other Pincerna species; inner peristome slightly protruding, sharp; the two peristomes are clearly separated; umbilicus open, slit-like.

Operculum. The operculum of one specimen could be examined. The inner surface is smooth, no central nipple observed ( Fig. 3A ). The outer surface nearly smooth, but its multispiral character discernible ( Fig. 3B ).

Radula. ( Fig. 3 C–E): Radula taenioglossate. Teeth arranged in v-shaped rows, each transverse row with seven teeth (2- 1-1-1-2). Rachidian tooth strongly constricted in its middle part, and having seven short, very attenuate cusps, of which the central one is the largest; the two cusps on either side of the central cusp subequal, whereas the single outermost cusp is very small. The inner marginal and the two outer marginal teeth have shallower constriction of the plates, and are longer and more slender than the central tooth. The inner marginal teeth have four cusps, the third (counting from the side of the rachidian tooth) is the largest. The outer marginal teeth have four very attenuate, triangular cusps.

ACKNOWLEDGEMENTS

I am grateful to Jonathan Ablett ( NHM), Virginie Héros (MNHN) for access to museum collections, to Wim J.M. Maassen for providing shells for study, Kurt Auffenberg for correcting the English, and to two anonymous reviewers for commenting on the manuscript.

LITERATURE CITED

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Measurements. Shell diameter: 2.4–2.6 mm, Shell height: 2.6–2.8 mm (n=3).

Baird W (1850) Nomenclature of Molluscous Animals and Shells in the Collection of the British Museum. Part I. Cyclophoridae. Printed by order of the trustees [by Spottiswoodes and Shaw], London, 69 pp.

Differential diagnosis. In shape and sculpture, Pincerna yanseni n. sp. resembles Pincerna liratula , which also inhabits Sumatra. However, P. liratula is much larger than the new species, the constriction between R2 and R3 is deeper, has a larger thickening on R3, and a weaker inner peristome. Moreover, some P. liratula populations have a more elongated tube. Two Sumatran subspecies of Alycaeus crenilabris are slightly larger, have much longer tubes, stronger radial ribs, and weaker spiral sculpture.

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Extralimital Pincerna species differ from P. yanseni n. sp. in the following shell characters: P. constricta: similar in size and shape to the new species, but has a more elevated spire, stronger and more widely-spaced ribs, weaker spiral striation; P. costata: similar in size, but has much stronger, more widely-spaced ribs, weaker spiral striation and stronger constriction; P. elegans: similar to the new species in terms of shell shape and size, but with denser ribs and much finer and denser spiral striation. Moreover, P. elegans has a thin projection of the outer peristome which occludes the umbilicus; P. khunhoensis: similar to the new species in shell size, but has a more elevated spire which results in a rather conical shell shape. Moreover, P. khunhoensis possesses stronger, more widely-spaced ribs, much weaker spiral striation, and a less expanded peristome.

Type locality. Indonesia, Sumatera Barat (West Sumatra), Solok Selatan (South Solok Regency), Koto Parik Gadang Diateh subdistrict, Goa [=cave] Pinti Kayu , near Sungai [=river] Dareh , approximate GPS position: 1.3027°S, 101.1164°E.

Distribution. Pincerna yanseni n. sp. is known from six localities in West Sumatra Province, Sumatra Island, Indonesia ( Fig. 4 ).

Remarks. The cross sectional view of the breathing tunnels have only been described in Alycaeus conformis ( Fulton, 1902) so far ( Páll-Gergely et al., 2016). In that species, the anterior crust folds over the posterior one, and has a blunt, but well-developed rib on the anterior crust. The formation of the breathing tubes is species or species group-specific (unpublished information), and should be described in details in as many alycaeid species as possible.

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Páll-Gergely B, Hunyadi A, Đỗ ĐS, Naggs F & Asami T (in press): Revision of the Alycaeidae of China, Laos and Vietnam (Gastropoda: Cyclophoroidea) I: The genera Dicharax and Metalycaeus. Zootaxa (in press).

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Figures

Fig. 1. Shells of Pincerna species. A, Pincerna constricta (Benson 1851) (type species of Cycloryx), NHMUK 1906.4.4.41 (syntype); B, Pincernayanseni n. sp. MZB.Gst. 18.970 (holotype); C,Pincerna liratula Preston, 1907 (type species ofPincerna), NHMUK 1907.5.20.191, (syntype). Scale = 1 mm, upper scale refers to A–B. Photos: H. Taylor (A, C) and B. Páll-Gergely (B).

Fig. 2. Details of the shell of Cycloryx yanseni n. sp. (all specimens were collected at the site IND.65). A, protoconch (specimen3); B, sutural tube and the corresponding breathing tunnels (specimen2); C–E, cross sectional view of the breathing tunnels (specimen1); F, schematic drawing of the breathing tunnels. Abbreviations: ac, anterior crust; pc, posterior crust; t, tunnel.

Fig. 3. Inner (A) and outer (B) side of the operculum and radula (C–E) of Pincerna yanseni n. sp. (population: IND.35).

Fig. 4. Distribution (filled circles) of Pincerna yanseni n. sp.