Boucardicus monchenkoi, Balashov, Igor & Griffiths, Owen, 2015

Balashov, Igor & Griffiths, Owen, 2015, Two new species of minute land snails from Madagascar: Boucardicus monchenkoi sp. nov. and B. ambindaensis sp. nov. (Caenogastropoda: Cyclophoridae), Zootaxa 4052 (2), pp. 237-240 : 237-238

Boucardicus monchenkoi sp. nov. Fig. 1 a.

Type locality. Coastal grassland near Hotel Dauphin (Avenue Gallien), Tôlanaro city (formerly Fort Dauphin), southeastern Madagascar.

Material. Holotype ( IZAN GT 4629) and 10 paratypes (7 in IZAN, GT 4630, 3 in AMS, C.483540) are directly from the type locality (collected by O. Griffiths in March 2001), 1 more paratype ( IZAN GT 4563) was collected "on the sandy hills with succulents 100-120 m from the ocean near Fort Dauphin" by V. I. Monchenko in February of 1991 together with some shells of the larger land snails.

Etymology. The specific name, monchenkoi , honors collector of the first known specimen—Prof. Vladislav I. Monchenko, Academician of National Academy of Sciences of Ukraine, founder of the Department of Invertebrate Fauna and Systematics of I.I. Schmalhausen Institute of Zoology.

Diagnosis. Shell is pupilloid-like, clearly ribbed, aperture is ovate-triangular with single well developed columellar lamella that goes from beginning of body-whorl till edge of the aperture and clearly visible in aperture. Peristome is complete, not reflected.

Dimensions. Height of shell 2.6–2.9 mm, diameter 1.3–1.5 mB. Holotype 2.7x1.5 mB. Aperture height 0.7–0.9 mm, aperture width 0.7–0.8 mB. Height of body whorl—1.1–1.2 mB. Diameter of embryonic whorls (~1.5) 0.4 mB. Diameter of 3rd whorl— 1 mm.

Shell is pupilloid-like, ovate-pointed, moderately thick-walled, not translucent, of 5–5.5 strongly convexed whorls. Suture is deep. Body-whorl periphery round. Coloration is brown (types are mainly lost their pigmentation). Embryonic whorls (~1.5) are smooth. Pre-constriction sculpture is regularly radially ribbed, on the 3rd whorl there are around 30 ribs in 1 mm (distance between ribs about 0.04 mm), on the 4th whorl—around 22 ribs in 1 mm (placed less regularly). First post-constriction ribs are same to 4th whorl, but placed more distantly. On the last 0.25 whorl before the peristome the ribs are much stronger. Body-whorl constriction occurs about 0.6 whorls before the peristome. The post-constriction swelling is moderate, about 0.3 mm width, placed left to columellar peristome. Aperture is ovate-triangular, with a single clear columellar lamella (peg) near edge of aperture in the middle of columellar peristome. Lamella is placed strictly perpendicularly to the columellar peristome, goes deeply in the aperture. Peristome is complete, not reflected, only slightly near umbilicus. Lip moderate. Umbilicus drop-shaped.

Variability. All 12 type specimens are very similar in size, shape, sculpture, swelling and aperture. An older specimen from the other locality is almost identical to the holotype. Therefore known variability of the shell is low in this species.

Identification. From the all other pupilloid-like species of the genus it differs by its complete aperture, from mostalso by its clearly ribbed shell. From B. menoi —by much more developed columellar lamella visible in aperture, presence of post-constriction swelling and larger shell. From B. delicatus and B. minutus —by much larger shell and much more developed columellar lamella.

Distribution and habitats. It is only known from coastal grasslands near Tôlanaro city (south-eastern Madagascar). This area was once covered in primary forest growing on coastal dunes and has now mostly been cleared.

Figures

FIGURE 1. Holotypes of Boucardicus monchenkoi sp. nov. (a) and B. ambindaensis sp. nov. (b).