Macrochlamys caverna 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 : 769-771

Macrochlamys caverna Pholyotha & Panha , new species

( Figs. 2C , 3E, F , 5A, B , 6G–I )

Material examined. Holotype ( Fig. 3E ; shell height 8.6 mm, shell width 17.2 mm, aperture height 5.6 mm, aperture width 8.0 mm, 6¼ whorls) ( CUMZ 7107 ), limestone outcrops at Wat Khao Samo Khon (Temple), Tha Wung District, Lopburi Province, Thailand, 14° 54′05.9″N, 100° 30′29.5″E . Paratypes: 55 shells ( Fig. 3F ; shell height 8.1 mm, shell width 15.0 mm, aperture height 5.4 mm, aperture width 7.2 mm, 6⅛ whorls) ( CUMZ 7108 ), seven specimens ( CUMZ 7109 ), five shells ( NHMUK), five shells ( ZRC.MOL.13772), same data as holotype. Non type material: 11 shells ( CUMZ 7110 ), three specimens ( CUMZ 7111 ), Wat Tham Chang Pueak (Temple), Tha Wung District, Lopburi Province, Thailand, 14° 54′08.7″N, 100° 30′08.6″E ; 20 shells ( CUMZ 7112 ), eight specimens ( CUMZ 7113 ), Khao Mon Ing Dharma Practice Place, Ban Chi, Ban Mi District, Lopburi Province, Thailand, 14° 55′29.0″N, 100° 31′00.3″E .

Etymology. The specific epithet “ caverna ” is derived from the Latin “ cavus ” meaning “hole or hollow”, in reference to the open and deep umbilicus.

Description. Shell medium-sized ( Fig. 3E, F ; shell height up to 8.6 mm; shell width up to 17.2 mm), dextral, depressed, somewhat thin, translucent, shiny, and pale reddish-brown. Shell surface smooth with obvious microscopic growth lines. Embryonic shell surface smooth, small with 2½ whorls. Whorls 5–6, regularly increasing. Suture wide and shallow. Spire convex, apex raised. Spire angle about 134–142°. Last whorl narrow with rounded periphery. Aperture ovate-lunate, obliquely open, lip simple. Columellar margin slightly thickened and reflected close to umbilicus. Umbilicus widely open and deep.

Genital organs. Atrium (at) short. Penis prolonged tubeshaped. Distal end with short and swollen penial caecum (pc) that corresponds to penial verge inside. Epiphallus (e) cylindrical, about two times penis length. Epiphallic caecum (ec) coiled about one circle and located proximally about one-third of epiphallic length. Penial retractor muscle (prm) short and thick. Flagellum (fl) enlarged and short, about one-third of epiphalic length. Vas deference (vd) a long, thin tube, connected between distal end of epiphallus and free oviduct ( Fig. 5A ).

Internal wall of penis proximally with oblique trapezoid penial pilasters (pp) and distally around penial caecum with long and narrowed pilasters surrounding penial verge (pv). Penial verge short, triangular-shaped and located at distal end of penis ( Fig. 5B ).

Vagina (v) about same length as penis and cylindrical. Dart apparatus (da) large and cylindrical, located at proximal end of vagina. Gametolytic sac (gs) prolonged and bulbous, gametolytic duct (gd) long and cylindrical. Free oviduct (fo) about same length as penis, proximally encircled with thick brownish tissue close to gametolytic duct and free oviduct junction at about one-fourth of its length. Oviduct (ov) large lobules; prostate gland (pg) running alongside oviduct ( Fig. 5A ).

Radula. Each row consists of 93 teeth with formula (47- (13-12)-1-(12-13)-45). Central tooth symmetrical tricuspid. Mesocone large and lanceolate. Lateral teeth asymmetrical tricuspid with small endocone, large mesocone. Ectocone larger than endocone. Elongate and obliquely bicuspid marginal teeth start from tooth number 12–13 ( Fig. 6G–I ).

External features. Animal with dark grey head and tentacles that gradually becomes paler posteriorly into the yellowish body and tail. Caudal foss (cf) and caudal horn (ch) large and slightly dark grey in colour. Mantle edge well developed, shell lobes and dorsal lobes grey, except right dorsal lobe (rdl) which has yellowish colouration ( Fig. 2C ). Snails secrete yellowish slime when disturbed.

Distribution and habitat. Population density of this new species was generally high and abundant where found. They tend to live in small limestone hills in the Tha Wung and Ban Mi Districts, Lopburi Province.

Remarks. Macrochlamys caverna new species can be distinguished by its rather depressed shell with a wide and shallow suture and a widely open and deep umbilicus. Its genitalia have a short penial caecum, one circle of coiled epiphallic caecum, a rather long vagina and free oviduct, and very large dart apparatus that is located at the base of the vagina opposite the penis. Radula morphology of this species is very similar to M. aurantia new species.

Macrochlamys caverna new species can be distinguished from M. aurantia new species and M. coleus new species by its more elevated spire, shallow suture, widely open umbilicus and oblique trapezoid penial pilasters on the penial wall. In contrast, both M. aurantia new species and M. coleus new species have a depressed spire, channelled suture, narrow umbilicus, and small wrinkled and longitudinal folds on the penial wall. The rounded last whorl and wide open umbilicus of this new species differs from M. benoiti ( Crosse & Fischer, 1863) from Indochina and M. malaccana ( Pfeiffer, 1854) from Peninsular Malaysia. Macrochlamys benoiti has a shouldered last whorl and narrow umbilicus, while M. malaccana has a comparatively broader last whorl and minute umbilicus.

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. 3. Shells of Macrochlamys aurantia new species (A, B), M. coleus new species (C, D), and M. caverna new species (E, F). A, Macrochlamys aurantia holotype (CUMZ 7101); B, paratype (CUMZ 7102); C, M. coleus holotype (CUMZ 7104); D, paratype (CUMZ 7105); E, M. caverna holotype (CUMZ 7107); F, paratype (CUMZ 7108).

Fig. 5. Genitalia of Macrochlamys caverna new species (A, B), and M. lemma new species (C, D). A, B, Macrochlamys caverna paratype (CUMZ 7109): A, whole reproductive system; B, internal structure of penis with penial verge.C, D, Macrochlamys lemma paratype (CUMZ 7116): 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. Asterisk indicates the tissue casting.

Fig. 6. SEM images of the radula of Macrochlamys aurantia new species (A–C) (paratype; CUMZ 7103), M. coleus new species (D–F) (paratype; CUMZ 7106), and M. caverna new species (G–I) (paratype; CUMZ 7109). 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).