Ganesella perakensis (Crosse, 1879)

Sutcharit, Chirasak, Thach, Phanara, Chhuoy, Samol, Ngor, Peng Bun, Jeratthitikul, Ekgachai, Siriwut, Warut, Srisonchai, Ruttapon, Ng, Ting Hui, Pholyotha, Arthit, Jirapatrasilp, Parin & Panha, Somsak, 2020, Annotated checklist of the land snail fauna from southern Cambodia (Mollusca, Gastropoda), ZooKeys 948, pp. 1-46 : 1

Ganesella perakensis (Crosse, 1879) Figs 5C , 12A

Helix (Geotrochus) perakensis Crosse, 1879: 199, 200, pl. 8, fig. 4. Type locality: Perak [Perak State, Malaysia].

Ganesella perakensis : Richardson 1985: 130. Sutcharit et al. 2019a: fig. 4d.

Material examined.

Locality no. 15: CUMZ-CM159 (3 shells; Fig. 12A ), CUMZ-CM160 (2 shells), CUMZ-CM161 (3 specimens in ethanol; Fig. 5C ). The snails were found to live on tree trunks and leaves.

Distribution.

Peninsula Malaysia ( Sutcharit et al. 2019a).

Remarks.

This species was originally described from Perak, Peninsula Malaysia, and a syntype was recently figured in Sutcharit et al. (2019a: fig. 4d). Characteristics of this species are its small shell size and trochoid shape. The whorls are slightly convex, with wide and shallow suture. The shell surface exhibits thin growth lines and thin corneous periostracum. The last whorl is with well-developed peripheral keel and blunt at lower periphery. The shell colour is pale yellow to brownish, with dark brown spiral bands on peripheral keel. The apertural lip is expanded, whitish, and angled.

Ganesella perakensis belongs to the G. acris (Benson, 1859) species complex which is composed of 11 nominal species and widely distributed from Western Ghats of India to Indochina and the Greater Sunda Islands (see Richardson 1985: 129, 130). However, G. perakensis differs from all species known in Indochina. It differs from G. subperakensis (Pilsbry, 1891) from “Tonquin” and G. vatheleti (Bavay & Dautzenberg, 1899) from "Van Bu, Tonkin" by having a strong peripheral keel. For comparison, G. subperakensis is convex below periphery, with less strong peripheral keel and without brownish spiral band ( Pilsbry 1891), while G. vatheleti exhibits a round last whorl and is more convex at base ( Bavay and Dautzenberg 1899).

This species is very similar to G. lantenoisi (Dautzenberg & Fischer, 1906), which was described from Ha-Giang (Northern Vietnam) and Siam [Thailand]. The description itself was based mainly on the Ha-Giang specimen ( Dautzenberg and Fischer 1906: pl. 9, fig. 10) while the Siamese specimen ( Dautzenberg and Fischer 1906: pl. 9, fig. 11) is more similar to G. perakensis . Thus, the type series of this species seems to comprise of two separate species, one from northern Vietnam and one from Thailand. Ganesella perakensis differs from G. lantenoisi (specimen from Ha-Giang) in having a smaller shell (shell height up to 13 mm), shallow suture with 6 to 7 convex whorls, while G. lantenoisi performs an elongate trochoid, larger shell (shell height up to 18 mm), suture flattened and smooth 9 to 10 whorls. However, further investigations with both genitalia and DNA analysis will be necessary to elucidate the exact relationship between them.

Figures

Figure 5. Living snails of A Amphidromus leucoxanthus (Martens, 1864) B Trichochloritis norodomiana (Morlet, 1883) C Ganesella perakensis (Crosse, 1879) D, E Anceyoconcha rhombostoma (Pfeiffer, 1861) D brownish morph and E dark brown morph and F Anceyoconcha chaudoensis (Rochebrune, 1881) comb. nov. All not to scale.

Figure 12. A Ganesella perakensis (Crosse, 1879) B Anceyoconcha siamensis obesula (Ancey, 1888) comb. nov. C, D Anceyoconcha rhombostoma (Pfeiffer, 1861). A white arrowhead indicates strong peripheral keel on the last whorl, the distinguished character of this species and E, F Anceyoconcha chaudoensis (Rochebrune, 1881) comb. nov.