Hunyadiscus tigrina, Pall-Gergely, 2018

Páll-Gergely, Barna, 2018, Systematic revision of the Plectopylinae (Gastropoda, Pulmonata, Plectopylidae), European Journal of Taxonomy 455, pp. 1-114 : 71-73

Hunyadiscus tigrina sp. nov.

urn:lsid:zoobank.org:act:563BC118-AE90-4801-8D47-9D4E78E32BDE

Figs 29C–D, 31C–D, 32C–D, 33

Plectopylis sp. – Tumpeesuwan & Tumpeesuwan 2010: 14, fig. 2g.

Diagnosis

Shell medium-sized, dextral, thin-walled, bluntly keeled, with red and yellow stripes and a conspicuously large protoconch; parietal wall with a single curved lamella without additional plicae; palatal wall with seven parallel, horizontal plicae.

Etymology

The name ‘tigrina’ (used as a noun) refers to the red and yellow stripes of this species, which resemble the markings of a tiger.

Material examined

Holotype

THAILAND: 1 shell (D = 13.9 mm), Udon Thani Province, limestone hill, 18 km W of Na Klang , slope of hill, leaf litter, 17°19′30″ N 102°1′48″ E, 400 m a.s.l., 23 May 1987, F.G. Thompson leg. ( UF 343843).

Paratypes

THAILAND: 62 shells, same data as for holotype ( UF 448579); 2 shells, same data as for holotype ( HNHM 97455); 10 specimens (preserved in ethanol; 3 in separate vials used for molecular study: PL060, PL061, PL062), same data as for holotype ( UF 343844); 4 shells, Loei Province, Phu Pha Ya Mountain, 5 km NNE of Ban Phia, gully, leaf litter, 17°34′31″ N, 101°51′23″ E, 800 m a.s.l., 22 May 1987, F.G. Thompson leg. ( UF 343809); 3 shells, Loei Province, Phu Pha Ya Mountain, 4 km NNE of Ban Phia, ravine, leaf litter, 17°34′7″ N, 101°51′32″ E, 750 m a.s.l., 21 May 1987, F.G. Thompson leg. ( UF 343782); 26 shells, Loei Province, limestone knoll, 1 km E of Ban Huai Muang, limestone dome, leaf litter, 17°28′26″ N, 101°53′20″ E, 375 m a.s.l., 21 May 1987, F.G. Thompson leg. ( UF 343745); 3 shells, same data as for preceding ( HNHM 97473); 80 shells (incl. some juv.), Loei Province, 6 km E of Wang Saphung, 17°17′28″ N, 101°50′25″ E, ca 300 m a.s.l., 23 May 1987, F.G. Thompson leg. ( UF 343817); 3 shells, same data as for preceding ( HNHM 97474); 10 specimens (preserved in ethanol: PL022 and PL023 used for molecular study), same data as for preceding ( UF 343818).

Description

SHELL. Dextral, lenticular, with bluntly keeled body whorl and conspicuously large protoconch; teleoconch with yellow and red transverse stripes, which are more prominent on ventral surface; fresh shells with periostracum with deciduous folds on keel; protoconch consists of three very finely regularly ribbed and densely spirally striated whorls; dorsal surface of teleoconch irregularly reticulate; entire shell with 5.25–6 regularly increasing whorls, separated by a rather shallow suture; ventral surface almost smooth; inner side of umbilicus irregularly finely ribbed; umbilicus moderately wide but not very deep; peristome only slightly thickened and reflected; parietal region with an additional, inconspicuous calcareous layer; apertural fold absent.

Five shells were opened. Parietal wall with a single, more-or-less vertical, curved lamella. Palatal wall with seven parallel plicae; first shortest and situated close to upper suture; second usually situated on keel, situated in comparatively large distance from first plica; last plica relatively short; middle plicae (third to sixth) usually straight, but slightly sinuate centrally; all plicae thicker anteriorly and thinner posteriorly; sometimes, additional short plicae can be seen above posterior end of last three plicae.

MEASUREMENTS (in mm). D = 12.8–17.3, H = 5.0–7.2 (n = 6).

CHARACTERS OF THE GENITAL SYSTEM. Two specimens were dissected (UF 343818). Right ommatophoral retractor runs between penis and vagina; penis short, internal wall bears a complex structure that is thickened and rounded in proximal part of penis, and divides to two equal ‘legs’ towards atrium; no epiphallic differentiation observed; retractor muscle thick, inserts on proximal end of penis; proximal part of penis contains very small, conical calcareous granules; distal end of vas deferens hidden, it derives near insertion of retractor muscle and becomes a free tube near proximal end of penis; free part of vas deferens very long, thickened near proximal end; vagina about as long as penis, internally with rather irregular, converging longitudinal folds; vaginal bulb slightly developed; bursa copulatrix short, with oval bursa; diverticulum absent.

RADULA. Centrals nearly entirely reduced; endocones of laterals rhomboid; ectocones of marginals undivided or divided to two; endocones of marginals mostly undivided, or divided by shallow incision.

Differential diagnosis

Hunyadiscus saurini has a shouldered body whorl, stronger spiral striation on the protoconch, a horizontal lower plica anterior to the lamella, and the fifth main palatal plica is strongly Z-shaped. In contrast, H. tigrina sp. nov. usually has a smaller, keeled shell, weaker spiral striation on the protoconch, possesses only a single lamella on the parietal wall, and all its palatal plicae are horizontal.

Distribution

The species is known from Loei and Udon Provinces, northern Thailand ( Fig. 12 ).

Figures

Fig. 12. Distribution of plectopylid species in Thailand, Laos and Myanmar. Legends: circle = Chersaecia shanensis (Stoliczka, 1873); filled square = Chersaecia reversalis sp. nov.; empty square = Chersaecia dextrorsa (Benson, 1860); empty rhomb = Hunyadiscus tigrina sp. nov.; filled rhomb = Hunyadiscus saurini Páll-Gergely, 2016; triangle, top up = Plectopylis crassilabris sp. nov.; triangle, top down = Naggsia laomontana (L. Pfeiffer, 1862); empty triangle, top down = Plectopylis bensoni Gude, 1914.