Macrochlamys tanymentula Pholyotha & Panha, 2018

Pholyotha, Arthit, Sutcharit, Chirasak & Panha, Somsak, 2018, The land snail genus Macrochlamys Gray, 1847 from Thailand, with descriptions of five new species (Pulmonata: Ariophantidae), Raffles Bulletin of Zoology 66, pp. 763-781 : 772-774

Macrochlamys tanymentula Pholyotha & Panha , new species

( Figs. 2E , 7C, D , 9A, B , 10D–F )

Material examined. Holotype ( Fig. 7C ; shell height 5.4 mm, shell width 10.9 mm, aperture height 4.2 mm, aperture width 5.3 mm, 5½ whorls) ( CUMZ 7117 ), limestone outcrops at Khao Lok , Tha Kha-nun Village, Thong Pha Phum District, Kanchanaburi Province, Thailand, 14° 44′13.7″N, 98° 38′30.7″E . Paratypes: one shell ( Fig. 7D ; shell height 5.5 mm, shell width 11.1 mm, aperture height 4.0 mm, aperture width 5.2 mm, 5¾ whorls) ( CUMZ 7118 ), nine specimens ( CUMZ 7119 ), same data as holotype .

Etymology. The specific name “ tanymentula ” is made up of the Greek word “ tany ” meaning “long or slender” and the Latin “ mentula ” meaning “male organ including epiphallus” to refer to the very long and slender epiphallus of the male organ.

Description. Shell medium-sized ( Fig. 7C, D ; shell height up to 5.5 mm; shell width up to 11.1 mm), dextral, globosely depressed, rather thin, shiny, translucent and light brown in colour. Shell surface smooth with thin growth lines. Embryonic shell smooth, with about 2½ whorls. Whorls 5–6, regularly increasing, with weakly impressed suture. Spire low conical to a little convex. Apex slightly raised with spire angle of about 151–154°. Last whorl large with rounded periphery. Aperture slightly large, ovately lunate in shape, obliquely open with simple lip. Columellar margin gradually reflected near umbilicus. Umbilicus narrowly open and very small.

Genital organs. Atrium (at) very short. Penis (p) short, enlarged cylindrical in shape, and about two times greater than epiphallus diameter. Epiphallus (e) small, a slender tube about five times longer than penis. Epiphallic caecum (ec) coiled about one circle and located at middle of epiphallus. Penial retractor muscle (prm) thin. Flagellum (fl) very long, slender, and about half of epiphallic length. Vas deference (vd) a thin tube connected between free oviduct and distal end of epiphallus ( Fig. 9A ).

Internal wall of penis with small wrinkled longitudinal penial pilasters (pp). Penial verge (pv) slightly small, cylindricalshaped and situated at distal end of penis ( Fig. 9B ).

Vagina (v) very short. Dart apparatus (da) large and cylindrical in shape, situated at proximal end of vagina. Gametolytic sac (gs) long and bulbous. Gametolytic duct (gd) long and cylindrical in shape. Free oviduct (fo) a small tube, approximately same length of penis, with thick brownish tissue near proximal end. Oviduct (ov) large lobules, with prostate gland (pg) running alongside ( Fig. 9A ).

Radula. Each row consists of about 99 teeth with formula (50-(14-12)-1-(12-13)-48). Central tooth symmetrical tricuspid with long and slender mesocone. Lateral teeth asymmetrical tricuspid with deeply indented endocone and ectocone. Bicuspid marginal teeth start from tooth number 12–14 ( Fig. 10D–F ).

External features. Animal with blackish grey reticulated skin, becoming pale yellow near foot sole and darker grey at eye stalks. Caudal foss (cf) large. Caudal horn (ch) raised with blackish grey colouration. Mantle edge well developed and blackish grey ( Fig. 2E ). Shell and dorsal lobes morphology similar to M. aurantia new species. Snails secrete yellowishgreen slime when disturbed.

Distribution and habitat. Macrochlamys tanymentula new species has a narrow distribution and is currently known only from the type locality with a low population density. Snails were found among leaf litter on the ground or crawling on limestone walls.

Remarks. Macrochlamys tanymentula new species can be distinguished by its globosely depressed shell, with wide shallow suture and a very narrow umbilicus. The genitalia

Pholyotha et al.: Macrochlamys species from Thailand have a very long and slender epiphallus and flagellum, coiled epiphallic caecum of about one circle, very short vagina, and a large dart apparatus located at the vagina base opposite the penis. Its radula morphology is very similar to M. aurantia new species.

This new species can be clearly distinguished from the other four new species proposed herein by its smaller shell with weakly impressed suture, narrow umbilicus, and very long epiphallus and flagellum, short vagina, and no penial caecum. The other four new species have relatively larger shells ( Table 1), shorter epiphallus and flagellum, and with a short penial caecum. Furthermore, M. aurantia new species and M. coleus new species have a channel-shaped suture and orange to pale orange body colour, while M. caverna new species and M. lemma new species have oblique trapezoid penial pilasters inside the penis.

Macrochlamys tanymentula new species differs from M. petasus ( Benson, 1859) and M. aspides ( Benson, 1863) from Myanmar by its rounded last whorl and simple apertural lip. In comparison, M. petasus has a rounded to slightly subangulated last whorl, and the inside edge of the peristome is slightly expanded, while M. aspides has a strongly thickened basal margin at the edge of the peristome ( Blanford & Godwin-Austen, 1908). Compared with M. notha Blanford, 1905 from Myanmar and M. brunnea from Thailand, M. tanymentula new species has a smooth shell surface, relatively large and thin shell, with a slightly wider umbilicus. Macrochlamys notha has a dull shell with radial sculpture while M. brunnea has a relatively smaller shell and narrower umbilicus. Macrochlamys stephoides Stoliczka, 1873 from Malaysia has a higher spire compared to the depressed spire of M. tanymentula new species. In addition, Stoliczka (1873) mentioned that M. stephoides has similar genitalia to M. indica Benson sensu Godwin-Austen, 1883 . In contrast, this new species has a very long epiphallus and flagellum (see Blanford & Godwin-Austen, 1908: 95).

Figures

Fig. 2. Living snails of Macrochlamys spp. from Thailand. A, Macrochlamys aurantia new species, paratype (CUMZ 7103), Thong Pha Phum, Kanchanaburi, shell width about 15 mm; B, M. coleus new species, paratype (CUMZ 7106), Sai Yok, Kanchanaburi, shell width about 15 mm; C,M. caverna new species, paratype (CUMZ 7109), Tha Wung, Lopburi, shell width about 17 mm; D, M. lemma new species, paratype (CUMZ 7116), Ban Mi, Lopburi, shell width about 15 mm; E, M. tanymentula new species, paratype (CUMZ 7119), Thong Pha Phum, Kanchanaburi, shell width about 10 mm; F, M. kelantanensis (CUMZ 7125), Lam Kaen, Phang-Nga, shell width about 20 mm.

Fig. 7. Shells of Macrochlamys lemma new species (A, B), and M. tanymentula new species (C, D). A, Macrochlamys lemma holotype (CUMZ 7114); B, paratype (CUMZ 7115); C, M. tanymentula holotype (CUMZ 7117); D, paratype (CUMZ 7118).

Fig. 9. Genitalia of Macrochlamys tanymentula new species (A, B), and M. kelantanensis (C, D). A, B, Macrochlamys tanymentula paratype (CUMZ 7119): A, whole reproductive system; B, internal structure of penis with penial verge. C, D, Macrochlamys kelantanensis (CUMZ 7125): C, whole reproductive system; D, internal structure of penis with penial verge. Abbreviations: at, atrium; da, dart apparatus; drm, dart retractor muscle; e, epiphallus; ec, epiphallic caecum; fl, flagellum; fo, free oviduct; gd, gametolytic duct; gs, gametolytic sac; hf, head filament; ov, oviduct; p, penis; pc, penial caecum; pg, prostate gland; pp, penial pilaster; prm, penial retractor muscle; pv, penial verge; ss, sperm sac; tf, tail filament; v, vagina and vd, vas deferens. Arrow indicates position of the penial verge.

Fig. 10. SEM images of the radula of Macrochlamys lemma new species (A–C) (paratype; CUMZ 7116), M. tanymentula new species (D–F) (paratype; CUMZ 7119), and M. kelantanensis Möllendorff, 1902 (G–I) (CUMZ 7125). Central tooth (indicated by ‘C’) with lateral teeth (A, D, G); lateral teeth with tricuspid marginal teeth transition (B, E, H); bicuspid marginal teeth (C, F, I).