Georissa sp.

Fig. 5A–K

Material examined

INDIA • 2 shells; Manipur, Bishnupur district, Sadu Chiru waterfall area; 24.742281° N, 93.743319° E; 1319 m a.s.l.; 28 Jul. 2018; Nipu Kumar Das leg.; AT/2018/ LS6010, AT/2018/ LS6011.

Measurements (in mm)

Shell 1 (AT/2018/ LS 6010, Fig. 5A–F): SH 2.05, SW 1.53, SH/SW 1.34, AH 0.89, AW 0.90, AH/AW 0.99, SpH 1.05, SpW 1.27, distance between spiral ribs on body whorl (apertural view) 0.08, PrW 0.31. Shell 2 (AT/2018/ LS 6011, Fig. 5G–K): SH 1.98, SW 1.63, SH/SW 1.21, AH 0.91, AW 0.98, AH/AW 0.93, SpH 1.06, SpW 1.35, distance between spiral ribs on body whorl (apertural view) 0.09, PrW 0.35.

Description of shell

Shell dextral, small, oval, turbinate; spire acuminate; colour amber; shell sculpture spiral ribs present, strong, somewhat closely arranged, and nearly regularly spaced across shell surface except protoconch, with 6–9 strong spiral ribs on body whorl, somewhat fine or less sharp and more densely spaced spiral striations on basal part of body whorl or in umbilical view, distance between spiral ribs on body whorl (apertural view) 0.09 mm, the radial ribs absent, fine growth lines across the shell; suture well-impressed, shoulder narrow; umbilicus narrow; whorls 3.5, convex; protoconch/teleconch transition zone distinct; protoconch brownish, round and globular, shiny and smooth, PrW 0.35; aperture round or slightly ovate, oblique or sub-vertical; peristome simple, and thin, parietal lip straight to concave, palatal lip continuous with body whorl, basal lip convex; columellar callus prominent and oblique, whitish; operculum unknown.

Habitat and distribution

The shells of Georissa sp. were collected from the soil-leaf litter sample near the Sadu Chiru waterfalls, Manipur. The area experienced heavy tourist footfall during the summer season.

Remarks

The newly collected shells are highly worn-out; hence, we are not describing them as a new species here, although they differ significantly from G. pyxis W.H. Benson, 1956. Shell 1 has a broken body whorl and aperture, with most of the shell sculpture eroded, while shell 2 has a broken aperture and partially eroded sculpture. Both shells retain some adhering dirt that is difficult to remove, given their poor condition and delicate state. The two shells differ from G. pyxis in several conchological characters. They are slightly larger (SH 1.98–2.05 mm, SW 1.53–1.63 mm) than G. pyxis (SH 1.5 mm, SW 1.25 mm) (Benson 1856). Additionally, they are proportionally wider than the syntype of G. pyxis, with shell 2 being markedly broader and possessing a more inflated body whorl, thereby resulting in a relatively lower spire compared to the more conical shell of the syntype. In shell 2, the spiral striation at the base of the shell (umbilical view) is conspicuously denser than in the syntype. Furthermore, the collection locality in Manipur, India, is more than 500 km from the type locality of G. pyxis (Thyet-Mio, Myanmar). Although microsnails are generally believed to have limited dispersal ability, recent studies have shown that some taxa may exhibit wider than expected distributions (e.g., Angustopila elevata Thompson & Upatham, 1997 – 2060 km, A. fabella Páll-Gergely & Hunyadi, 2015 – 640 km, A. szekeresi Páll-Gergely & Hunyadi, 2015 – 650 km, A. huoyani Jochum, Slapnik & Páll-Gergely, 2014 – 500 km; Páll-Gergely et al. 2023). Therefore, geographic distance alone cannot be regarded as definitive evidence for species-level delimitation. Nevertheless, when considered in conjunction with the observed shell morphological differences, the geographic disjunction provides additional support for treating the present material as distinct from G. pyxis and assigning it to Georissa sp., pending further evidence, such as anatomical or DNA evidence. The new collection represents the first record of the genus Georissa from the state of Manipur, India.