Ganesella rhombostoma (Pfeiffer, 1861)

Sutcharit, Chirasak, Backeljau, Thierry & Panha, Somsak, 2019, Re-description of the type species of the genera Ganesella Blanford, 1863 and Globotrochus Haas, 1935; with description of a new Ganesella species from Thailand (Eupulmonata, Camaenidae), ZooKeys 870, pp. 51-76 : 51

Ganesella rhombostoma (Pfeiffer, 1861) Figs 1C , 3 C–I , 5 E–G , 7 D–F , 8

Bulimus rhombostomus Pfeiffer, 1861: 194, 195. Pfeiffer 1868: 33.

Amphidromus rhombostomus : Pfeiffer and Clessin 1881: 214. Morlet 1889: 127. Morlet 1890: 121, 122, pl. 3, figs 6, 6a, b. Fischer and Dautzenberg 1904: 407.

Buliminus rhombostomus : Dautzenberg and Fischer 1906: 366, 367.

Buliminus rhombostomus var. pupoidea Dautzenberg and Fischer 1906: 367. Type locality: Hong-Chon, Cochinchine.

Giardia rhombostoma : Schileyko 2011: 46.

Pseudobuliminus harryleei Thach, 2017: 54, 55, figs 756-760. Type locality: Suburb of Battambang City, Battambang Province, Northwest Cambodia. New Synonym

Pseudobuliminus tuongvyae Thach, 2017: 56, figs 751-755. Type locality: Ha Tien, Kien Gaing Province, Southwest Vietnam. New Synonym

Pseudobuliminus huberi Thach, 2017: 55, figs 759-760. Type locality: 20 km of Kampong Trach District, Kampot Province, Northwest Cambodia. New Synonym

Type locality.

Camboja [Cambodia].

Material examined.

Type specimens. Three syntypes of Bulimus rhombostomus Pfeiffer, 1861 in H. Cuming collection, the shell that best matches with the original description is designated here as the lectotype NHMUK 20130215/1 ( Fig. 3C , height 16.7 mm, width 11.5 mm) to stabilize the name; the other two shells from the same lot become the paralectotypes NHMUK 20130215/2-3 (2 shells; Fig. 3D , height 18.4 mm, width 13.2 mm).

Additional material.

VIETNAM: Ha Tien, Kien Gaing Province, Southwest Vietnam: holotype of Pseudobuliminus tuongvyae Thach, 2017 MNHN-IM-2000-33203. CAMBODIA: Suburb of Battambang City, Battambang Province, Northwest Cambodia: holotype of Pseudobuliminus harryleei Thach, 2017 FMNH 381985 ( Fig. 3E ). Wat Thammaban Khiri, Sirisophon Town, Banteay Meanchey Province (13°37'58.1"N, 102°56'38.0"E): CUMZ 5131 ( Fig. 3H ). THAILAND: Tam Leoum, Klonghad District, Srakaeo Province: CUMZ 4286 ( Fig. 3I ). Tam Pha Pheung, Klonghad District, Srakaeo Province: CUMZ 5124. Tam Srithong, Klonghad District, Srakaeo Province: CUMZ 4070, 5118, 5132 ( Fig. 3F ). Tam Phet Phothong, Klonghad District, Srakaeo Province: CUMZ 4600, 5119. Khoa Phlapphueng Thong, Wang Somboon District, Srakaeo Province: CUMZ 4069. Wat Khao Maka, Muang District, Srakaeo Province: CUMZ 4071, 4598, 4599, 5130 ( Fig. 3G ). Tam Kaeo Sawanbandan, Pong Namron District, Chanthaburi Province: CUMZ 4285.Tam Rad, Tha Takiep District, Chachoengsao Province: CUMZ 5117.

Description.

Shell. Shell small, sinistral, thin and trochoid. Apex acute with blackish colour; embryonic shell smooth. Whorls 5-6, increasing regularly, convex; suture wide and shallow. Shell surface smooth or with fine growth lines. Last whorl large, well rounded, keeled near aperture; with or without brownish spiral band. Shell monochrome white, yellow to light brownish and translucent. Aperture semi-ovate, open subventrally; lip expanded and whitish; parietal callus transparent. Umbilicus rimate; columella wide and whitish.

Genital organs. Atrium (at) short (N = 10). Penis (p) cylindrical, long and may be as long as the vagina. Epiphallus (e) and flagellum (fl) each about half as long as the penis. Vas deferens (vd) long and narrow, extending from free oviduct and connected to distal part of epiphallus. Penial retractor muscle (pr) long and slightly thickened ( Fig. 5E ).

Penial verge (pv) small, conical, and with smooth surface. Penial wall ribbed, forming a series of irregular, smooth longitudinal pilasters (pp) that encircle penial verge ( Fig. 5F ).

Vagina (v) large, cylindrical about as long as penis. Gametolytic duct (gd) short, cylindrical, gradually tapering towards gametolytic sac (gs). Free oviduct (fo) short, about half as long as vagina; oviduct (ov) enlarged with curled lobules. Albumen gland (ag) curved ligulate. Hermaphroditic duct (hd) convoluted and connected to hermaphrodic gland (hg) ( Fig. 5E ).

Vaginal wall with several smooth, longitudinal pilasters; vaginal wall itself with strong longitudinal ridges through the vaginal chamber ( Fig. 5F ).

Radula. Teeth arranged in nearly straight rows, each row containing 58 (29-(6-9)-1-(7-9)-28) teeth. Central tooth triangular, symmetric monocuspid with dull cusp. Lateral teeth asymmetric, teeth no. 1-6 monocuspid and no. 7-10 bicuspid with very small ectocone ( Fig. 7D, E ). Marginal teeth start from teeth no. 9-10, tricuspid, endocone very small to absent, mesocone large triangular, and ectocone very small with pointed cusp. Outermost marginal teeth (near radula edge) tricuspid, endocone small, mesocone large with curved cusp, and ectocone with one, two or more pointed cusps ( Fig. 7E, F ).

Jaw crescent, with anteriorly convex cutting margin. Vertical ribs thin, and variable in number and size ( Fig. 5G ).

Distribution.

This species was formerly known from its type locality in Cambodia ( Morlet 1889, 1890) and some inaccurate localities recorded from Vietnam ( Schileyko 2011). In Thailand, it is known from several localities in Chachoengsao, Srakeo and Chanthaburi Provinces.

Remarks.

Ganesella rhombostoma has long been overlooked and its taxonomic status has been unclear. The species has been erroneously assigned to Amphidromus Albers, 1850 and Giardia Ancey, 1907 (see Dautzenberg and Fischer 1906, Schileyko 2011). Yet, its trochoid shell and sub-ventrally opening aperture show that it belongs to neither of these genera, since Giardia (type species Bulimus siamensis Redfield, 1853) and Amphidromus (type species Helix perversus Linnaeus, 1758) have an elongate, ovate shell, a non-deflected last whorl, an ovate and laterally opening aperture, and a narrowly opened umbilicus (see also Schileyko (2003) and Sutcharit and Panha (2006) for further comparisons). Moreover, the anatomical evidence presented here suggests that this species rather belongs to Ganesella . However, the relationships between Ganesella and Giardia needs further investigation by molecular analysis.

Specimens from isolated limestone outcrops at Khao Maka, Chacheongsao are smaller and have a more ovate shell without a brownish spiral band on of the last whorl ( Fig. 3G ). However, anatomically they are indistinguishable from typical G. rhombostoma and, therefore, they are considered conspecific.

Figures

Figure 1. A, B Ganesella carinella from Keng-khoy, Saraburi (shell width about 15 mm) A live snail and B snails aestivated under loose tree bark, and with white epiphrams attached on substrate C Ganesella rhombostoma from Klong Had, Srakeo (shell height about 15 mm) D Globotrochus onestera from Cuc Phuong, Vietnam (shell width about 15 mm).

Figure 3. A, B Ganesella carinella A shell from Lopburi CUMZ 4282 and B shell from Tam Brichinda, Chiangmai CUMZ 4165 C-I Ganesella rhombostoma C lectotype NHMUK 20130215 / 1 D paralectotype NHMUK 20130215 / 2 - 3 E shell of " harryleei Thach, 2017 " from Cambodia FMNH 381985 F shell from Klonghad, Srakeo CUMZ 5132 G shell from Chachoengsao CUMZ 5130 H shell from Sirisophon, Cambodia CUMZ 5131 and I shell from Srakaeo CUMZ 4286.

Figure 5. A-D Ganesella carinella from Saraburi A general view of genital system B internal structure of penis and vagina C pallial system and pulmonary cavity and D jaw E-G Ganesella rhombostoma from Srakaeo E general view of genital system F internal structure of penis and vagina and G jaw.

Figure 7. Radula. A-C Ganesella carinella D-F Ganesella rhombostoma and G-I Globotrochus onestera A, D, G central tooth with the first to the second lateral teeth B, E, H lateral teeth with the tricuspid marginal teeth transition C, F, I outermost marginal teeth. Numbers indicate order of lateral and marginal teeth. Central tooth indicated by ' C'.

Figure 8. Geographic distribution of Ganesella spp. and Globotrochus spp.