Fansipanica milae Páll-Gergely & Dedov sp. nov.

Figs 1, 2, 3, 4

Type material.

Holotype (D: 12.8 mm, H: 9.5 mm); • Vietnam, Northern, Lào Cai Province, Sa Pa district, Fansipan Peak, bamboo forest below the peak, 22.3046°N, 103.7759°E, ca 3040 m, 24 X 2023, leg. I. Dedov, N. Simov, R. Bekchiev, M. Langurov, HNHM 105552. Paratypes: • IBER Coll. No. 40619/2, same locality; IBER Coll. No. 40633/1, same locality, 22.3052°N, 103.7756°E, ca 3033 m, 09 X 2025, leg. N. Simov, K. Ivanov.

Description.

Body. Body surface granular, uniformly dark grey coloured, including long eye tentacles. Area around genital pore smoother and paler. The sole is also paler, whitish-yellowish.

Shell. The shell of the living animal is dark brown coloured with brown-reddish hue, in preserved specimens pale reddish brown. The shell is fragile, medium sized, globose, slightly wider than high, the subsutural furrow is absent, the body whorl is rounded. The 4.25–4.5 regularly increasing whorls are separated by a shallow suture. The protoconch is consisting of 1.25–1.5 whorls, and bears dense, oval scales. This sculpture abruptly changes to the teleoconch sculpture at the protoconch-teleoconch boundary. The teleoconch is evenly covered by widely spaced hairs (where absent: raised, papilliform hair scars). The hairs are permanent on the entire shell. The hair density is higher on the ventral side near the umbilical area than on the dorsal side and the periphery of the last whorl. The aperture is semilunar, slightly oblique to shell axis (prosocline). The parietal callus is absent, the parietal region is only indicated with an additional thin, transparent calcareous layer. The peristome is pinkish-reddish, slightly expanded and reflected only near the umbilical area. The umbilicus is extremely narrow, almost covered by the reflected peristome.

Measurements.

D = 11.9–12.8 mm, H = 9.4–9.8 mm (n = 3).

Genital organs.

The atrium is short. The penis is long, nearly cylindrical, its proximal (“ apical ”) third is covered with a thin penial sheath. The inner wall of penis is covered by irregular, slightly serrate longitudinal wrinkles, which gradually becoming stronger (more elevated) and more regular from the atrium towards the proximal end, where their number is five. The penial verge is small, conical, opening along a slit that ends close to its tip. The thick penial retractor muscle inserts at the penis-epiphallus junction. The epiphallus is slender, slightly shorter than the penis, internally with a single, elevated fold. A small, blunt flagellum marks the boundary between epiphallus and vas deferens. The vas deferens is only slightly more slender than the epiphallus. The vagina is slightly shorter than the penis, its distal part (closer to the atrium) is attached to the body wall with numerous fibres. The inner wall of the vagina bears numerous (~ 10) slender folds that are variable in width. The folds (mostly their distal parts) are slightly serrate, and the inner wall of the proximal part of the vagina (closer to the spermoviduct) is finely sculptured by a maze-like structure. The stalk of the bursa copulatrix is very long (> 2 × longer than the penis), approximately as wide as the epiphallus. The bursa was torn off when the animal was pulled out of its shell, therefore its morphology could not be examined.

Differential diagnosis.

The most similar species is F. gereti (Bavay & Dautzenberg, 1900), comb. nov. due to the similar size (although it is slightly larger), the shape of the shell and the (nearly) closed umbilicus. However, the new species has much denser hairs on the entire shell surface and has a darker peristome.

Etymology.

The species is named after Ivailo Dedov’s wife Mila Taseva, for her support over the years and patience during the long field trips.

Habitat.

Fansipan Mountain and the adjacent areas in Lao Cai Province (western part of the Hoang Lien Mountains) are a very unique region in northern Vietnam, where a large area of closed canopy primary forest in a mountain habitat persists. Nowadays, due to excessive utilisation, the tropical rainforest is only maintained in disconnected patches. The total number of species that can still be described makes the area rich (Sobey 1997). Hoang Lien National Park is located in the Hoang Lien Mountain Range with Fansipan Peak, which is considered the highest mountain in Vietnam, at 3143 m a. s. l. (Nguyen et al. 2022). The mollusc fauna of this region is almost unknown (Páll-Gergely et al. 2015).

Fansipanica milae Páll-Gergely & Dedov, gen. et sp. nov. was found at an altitude of ca 3040 m. The topography here is diversified: the mountain chains alternate with steep slopes and some relatively flat areas appearing like soil hills. The forest in the area of peak was protected from human activity by the long and high slopes, so that it appeared in pristine condition. At this altitude, in addition to the species from the families of Fagaceae and Lauraceae, Ericaceae (Rhododendron) was present as well as Theaceae (Ternstroemia) and Platanaceae (Platanus). On lower slopes and relatively flat places, Fagaceae, Lauraceae, Platanaceae, Sterculiaceae, Elaeocarpaceae, Magnoliaceae, Araliaceae, Aceraceae, Betulaceae, Ericaceae, Theaceae, Rhodoleiaceae, Cupressaceae (young trees), Verbenaceae, Rosaceae, Juglandaceae, and Aquifoliaceae dominate. One specific characteristic of this mountain assemblage is the bamboo forest (cf. Arundinaria) under the canopy. On the mountain chains and steep slopes, Theaceae, Ericaceae, Magnoliaceae, Rhodoleiaceae, Lauraceae, Cupressaceae, Aceraceae, Betulaceae, and Rosaceae families are present. The epiphytic plants include Orchidaceae, Lycopodiaceae, Polypodiaceae, Aspleniaceae, Davalliaceae, Hymenophyllaceae, Vittariaceae, Lepidopteridaceae, Gesneriaceae, Ericaceae, Bryophyta, and also Rosaceae and Araliaceae (Sobey 1997).