Ampelita decaryi Fischer-Piette, 1952

Fig. 13

Ampelita decaryi: Fischer-Piette 1952: 13, pl. 1, figs 7–9; Emberton 1990: fig. 4d, 1994: 176; Fischer-Piette et al. 1994: 97, pl. 7, figs 4–16. Type loc.: Madagascar.

Locality data: Antsingimavo: st’n 04/06. Kelifely Plateau: st’ns 08/05, 10/05. Tsingy de Bemaraha: st’n 15/96.

Distribution: Restricted to central western Madagascar; currently recorded only from Tsingy de Bemaraha and Antsingimavo. Not yet recorded from Tsingy Beanka, but known in subfossil form from the Kelifely Plateau. A record from the Ambositra area (Emberton 1994) almost certainly represents A. caderyi (see below).

Habitat: Dry mixed deciduous-evergreen forest on karst outcrops. No living specimens found, but considerable numbers of empty shells were collected from slots within the tsingy and under overhangs.

Remarks: The holotype of this species had no provenance beyond ‘Madagascar’, but Fischer-Piette (1952) mentioned a young individual from ‘Antsingy (Madagascar Ouest)’. Emberton (1990) and Fischer-Piette et al. (1994) placed this locality in the region of Tsingy de Bemaraha and additional material has since been found there (Griffiths, st’n 15/96). Emberton (1994) also identified under this name specimens from non-calcareous, rain forest habitats in the Ambositra area (Fianarantsoa Province). However, in reality this latter material is more probably referable to A. caderyi FischerPiette et al., 1994, the type locality for which lies in the same vicinity. Although they are undoubtedly similar, the differences between the two taxa were clearly stated by Fischer-Piette et al. (1994).

In terms of shape and coloration, the Antsingimavo material closely resembles the holotype of A. decaryi figured by Fischer-Piette (1952). However, whilst some adult shells in the Antsingimavo population match the holotype in size (max. diameter 35mm), most are somewhat larger (max. diameter reaching 42 mm). The abundance of empty shells indicates that the species was once not uncommon at this locality. Though much of this material is clearly old, some specimens were of fresh appearance and retained the periostracum, indicating that the species is probably still extant at the site, even though we found no live specimens during our survey. Subfossil shells from the Kelifely Plateau (Fig. 13G) are indistinguishable from the Antsingimavo material, except that the colour pattern is much faded.