Bathia madagascariensis Robson, 1914

Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, African Invertebrates 54 (1), pp. 1-48 : 29-30

Bathia madagascariensis Robson, 1914

Fig. 21

Bathia madagascariensis: Robson 1914: 383 , pl. 35, figs 11–13; Fischer-Piette et al. 1966: 11; 1994: 203, text-fig. 94, pl. 31, figs 10–12; Schileyko 2002: 1242, fig. 1633. Type loc.: ‘Namoroku (Ambon-go)’ [= Namoroka].

Locality data: Namoroka: st’n 930/97. Tsingy Beanka: st’ns 03/12, 06/12.

Distribution: Recorded only from the Tsingy de Namoroka Strict Nature Reserve and Tsingy Beanka in north-western Madagascar.

Habitat: Dry deciduous forest on limestone; dead shells have been found reasonably commonly at two sites in the southern part of Tsingy Beanka , in a cave and under overhangs. The snail occurs in similar conditions at Namoroka.

Remarks: Bathia madagascariensis was previously known only from the Namoroka Reserve, which lies approx. 180 km to the north-east of Tsingy Beanka . The present record of its occurrence in Tsingy Beanka represents a considerable southward range extension.Although only dead shells were found at this locality, some of these are fresh, indicating that the species is almost certainly still extant there.

Specimens from Tsingy Beanka attain a larger size than those at Namoroka (max. height 12.9 mm, max. diameter 25.5 vs 10.5 mm and 19.5 mm respectively at Namoroka). Furthermore, in Tsingy Beanka material the spire whorls are raised above the final whorl, but are level with it in Namoroka specimens (compare Figs 21A and 21D ). In the absence of evidence to suggest otherwise, we consider these differences to reflect geographical variation. As noted by Fischer-Piette et al. (1966) and Schileyko (2002), determination of the true affinities of this species must await morphological examination of the soft parts. Its placement in the Helicarionidae follows Fischer-Piette et al. (1994), but must be considered provisional.

Figures

Fig.21. Bathia madagascariensis Robson,1914:(A–C)Tsingy Beanka, st’n 03/12, max.diameter 24.4 mm, NMSA L8829; (D) Tsingy de Namoroka, st’n 930/97, max. diameter 19.5 mm, NMSA L8828.