Barringtonica montana, Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 65-71

Barringtonica montana n. sp.

( Figs 25I; 26J; 29B; 31B; 33B; 35B; 37B)

Etymology. From the Latin montanus = belonging to mountains, referring to the mountain-top existence of the species.

Diagnosis. Shell very small, pale golden-brown, weakly biconcave to planispiral, spire slightly depressed. Protoconch sculpture consisting of 27 low, flattened, broad spiral cords and a few very weak, widely spaced, radial growth ridges which are more noticeable at the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, slightly sinuate, opisthocline radial ribs. Ribs on body whorl 97–110 (mean 103). Umbilicus open U-shaped. Penis with an expanded apical portion becoming tubular distally; no pilaster formation observed; verge absent.

Type material examined. Holotype. AM C.472891, Polblue Crown Reserve , Pheasant Creek road, off Scone- Gloucester road, east of Scone , upper Hunter region, western Barrington Tops NP, NSW (31˚52’ 40” S, 151˚27’ 08” E), 2.ix.2001, coll. M. Shea. Paratype. AM C.472876, same data as holotype .

Description. Shell very small, pale golden-brown, weakly biconcave to planispiral, spire slightly depressed. Whorls 3.50, tightly coiled, the last weakly expanding and descending in front. Sutures strongly impressed. Shell diameter 3.47–3.60 mm (mean 3.53 mm), height 1.81–1.92 mm (mean 1.87 mm), H/D 0.52–0.53 (mean 0.52). Protoconch flat, of 1.12 whorls, diameter 0.61–0.64 mm. Protoconch sculpture consisting of 27 low, flattened, broad spiral cords and a few very weak, widely spaced, radial growth ridges which are more noticeable at the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, slightly sinuate, opisthocline radial ribs. Ribs on body whorl 97–110 (mean 103); width of rib interstices on the first teleoconch whorl less than width of three ribs to less than four ribs, width of rib interstices on the penultimate whorl equal to width of three to less than six ribs; each rib with two or more overlapping periostracal blades. Interstitial sculpture of low prominent microradial ribs and low, weaker microspiral cords forming weak beads at their intersection; number of microradials between ribs on the first teleoconch whorl 5–6. Aperture acutely, broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus open U-shaped, diameter 0.66–0.77 mm (mean 0.72 mm), D/U 4.47–5.42 (mean 4.91). Based on two measured adults.

Reproductive tract with ovotestis containing two clumps of alveoli, with undeveloped alveolar lobes. Hermaphroditic duct narrow crescent-shaped. Spermatheca with a medium sized oval bulb. Penial retractor muscle inserting on head of the penis at the junction of the penis and epiphallus. Epiphallus longer than penis, entering penis through a simple pore (i.e. verge absent). Penis tubular with an expanded apical portion becoming tubular distally, no pilaster formation observed. Vagina shorter than penis. Atrium short.

Distribution and habitat. Known only from the volcanics of the western Barrington Tops National Park, NSW; occurring in sub-alpine eucalypt woodland and forest (Snow Gum/Ribbon Gum association) with tussock grass ( Poa sp. ) groundcover on basalt, living under logs on soil surface.

Remarks. Barringtonica montana n. sp. differs from the microsympatric B. polblue chiefly in the size and shape of the umbilicus which is a much narrower U-shape in the former compared with the wide cup-shape in the latter. The narrower umbilicus of B. montana may be a character shift related to the microsympatry of the two congeners. Unfortunately the reproductive organs of specimens of both species were under-developed either due to immaturity or seasonally-induced regression and were unable to provide additional data. This is one of the few recorded incidences of congeneric sympatry in the species of eastern Australian land snails ( Stanisic et al. 2010). Among a fauna that may have evolved in response to climate induced fragmentation of mesic habitat, such instances of microsympatry are only liable to occur in the larger rainforest massifs such as the Barrington Tops (and also e.g. Wet Tropics, Border Ranges) where the likelihood of habitat reconnection under suitable climatic (wetter) conditions in the past was greatest.