Leiostyla beatae, Walther, Frank & Hausdorf, Bernhard, 2015

Walther, Frank & Hausdorf, Bernhard, 2015, Leiostyla beatae n. sp. from eastern Georgia (Gastropoda: Lauriidae), Zootaxa 3941 (1), pp. 144-148 : 144-147

Leiostyla beatae n. sp.

Diagnosis. A Leiostyla species characterized by a cylindrical-ovate, rib-striated shell with a columellar lamella forming a wide upwards bending arch.

Shell ( Fig. 1 A). Cylindrical-ovate; perforate; rib-striated (12–15 ribs per mm of the penultimate whorl), corneous; 6.75–7.25 slightly convex whorls separated by a slightly impressed suture; body whorl ascending towards the aperture; outside of the palatal wall with a distinct incision corresponding to the lower palatal fold; aperture cordate; peristome expanded and strengthened by a lip; angular lamella very high, without appendages; parietal lamella low; both are connected with the insertions of the peristome by a more or less thin callus; columellar lamella forming a wide upwards bending arch, inserting in a sharp angle and ending at the middle of the columellar edge; the suprapalatal fold is toothlike and forms a roundish sinulus with the angular lamella; upper palatal fold absent; lower palatal fold long and strong, below the middle of the palatal wall, fused anteriorly with the lip; basal fold long, also reaching the lip.

Measurements (n=27): shell diameter D: 1.80–2.16 mm, mean 1.94 + 0.09 mm; shell diameter at third whorl D3: 1.12–1.46 mm, mean 1.26 + 0.09 mm; shell height H: 3.40–3.92 mm, mean 3.64 + 0.17 mm; aperture diameter ad: 1.06–1.32, mean 1.19 + 0.07 mm; aperture height ah: 1.14–1.44, mean 1.29 + 0.08 mm; D/H: 0.484–0.818, mean 0.535 + 0.031.

Remarks. Leiostyla beatae has been identified with Leiostyla silicea ( Schileyko, 1975) ( Fig. 1 B) by Pokryszko et al. (2011). It differs from that species in the more cylindrical, lighter shell, the columellar lamella that is bending upwards and not running horizontally, and the lack of an upper palatal fold. Pilsbry (1922–1923) classified the species with a steeply ascending columellar lamella, namely Leiostyla paulinae ( Lindholm, 1913) and Leiostyla caucasica ( L. Pfeiffer, 1857) , in a separate section. The shape of the columellar lamella of L. beatae resembles that of these species. However, L. beatae differs from L. paulinae ( Fig. 1 C) in the cylindrical, more strongly rib-striated shell and the lack of an upper palatal fold and from L. caucasica ( Fig. 1 D) in the smaller, rib-striated shell.

A discriminant analysis based on the shell measurements (D, D3, H, ad, ah) of L. beatae , L. silicea and L. paulinae ( Fig. 2 ) indicated that the null hypothesis that the means of all of these variables are equal across the species can significantly be rejected (Wilk's lambda for the first two discriminant functions = 4.4%; p <0.001). Based on shell measurements alone, 96.9% of the individuals were correctly classified using the first two discriminant functions (93.8% after cross validation). Note, however, that we consider also the shell sculpture and the apertural armature as essential for the determination of L. beatae .

Type material. Holotype: Georgia: Lagodekhishevi valley 2 km upstream of Lagodekhi ( ZMH 101605, D = 1.9 mm, H = 3.8 mm, ad = 1.3 mm; ah = 1.4 mm). Paratypes: Georgia: Lagodekhishevi valley 2 km upstream of Lagodekhi (FW 7137/28; NHMW /4; ZMH 101606 /3).

Type locality. Georgia: Lagodekhishevi valley 2 km upstream of Lagodekhi, dry scree on a steep slope with mixed deciduous forest ( Carpinus , Fraxinus , Fagus ) and a dense undergrowth of Rubus and some Corylus bushes, 705 m a.s.l., 41.8563°N 46.2996°E.

Distribution (Fig. 3). Leiostyla beatae is known only from the type locality. Despite the land snail fauna of the Lagodekhi Nature Reserve is relatively well known ( Lezhawa 1983; L. Mumladze, pers. comm.), the new species has been detected only recently ( Pokryszko et al. 2011) because of its special microhabitat, which is difficult to access due to steepness and thorny vegetation. Only empty shells were found in the leaf litter. A systematic survey of suitable habitats in eastern Georgia and western Azerbaijan will probably reveal additional populations.

Etymology. The species is named in honour of Prof. Dr. Beata Pokryszko, Wrocław, who discovered the first specimens.

FIGURE 3. Distribution of Leiostyla beatae n. sp., Leiostyla caucasica , Leiostyla paulinae and Leiostyla silicea in the Caucasus region (0.5° grid).

Figures

FIGURE 1. Shells of Leiostyla species. A – C. Leiostyla beatae n. sp., Georgia: Lagodekhishevi valley 2 km upstream of Lagodekhi; A. holotype (ZMH 101605); B. paratype (NHMW); C. paratype (ZMH 101606); D. Leiostyla silicea (Schileyko, 1975), Georgia: Tekhuri valley 6.7 km towards Lebarde (ZMH 86618); E. Leiostyla paulinae (Lindholm, 1913), Georgia: Kintrishi valley, Chakhati (ZMH 81306); F. Leiostyla caucasica (L. Pfeiffer, 1857), Georgia: Pasanauri, lower valley of Shavi Aragvi river (ZMH 81326). Scale bar = 1.0 mm for all figures except oblique view into aperture; scale bare = 0.5 mm for oblique view into aperture.

FIGURE 2. Separation of Leiostyla beatae n. sp., Leiostyla silicea and Leiostyla paulinae according to the first two discriminant functions based on shell measurements.