Aenigmatoconcha clivicola, Tumpeesuwan & Tumpeesuwan, 2017

Tumpeesuwan, Chanidaporn & Tumpeesuwan, Sakboworn, 2017, Discovery of an overlooked Helicarionid land snail (Helicarionidae: Durgellinae) from northeastern Thailand, with description of a new genus and new species, and note on radula morphology and genital system, Raffles Bulletin of Zoology 65, pp. 181-188 : 184

Aenigmatoconcha clivicola , new species

Figs. 2–5 ; Tables 2–4

Helicarionidae gen. indet.: Tanmuangpak et al., 2012: 18–24. Sophina sp. : Tanmuangpak. 2016: 93–94.

Type material. Holotype: NHMSU-0013 ( Fig. 3 ) (SH 9.6 mm, SW 16.9 mm), Phu Pha Lom Limestone Hill in Mueang District , Loei Province, Northeastern Thailand, coll. K. Tanmuangpak, November 2012 . Paratypes: NHMSU-0014 (genital system and radula, Figs. 4–5 ), NHLRU-0006 (one specimen in 70% ethanol and one shell), ZRC.MOL.9413 (one shell), THNHM-IV-18003 (one shell), same locality as holotype, coll. K. Tanmuangpak, November 2012 – May 2014 .

Etymology. The specific epithet “ clivicola ” comes from two Latin words: “clivus”, meaning sloping side of hill, and “-cola”, meaning dweller.

Diagnosis. As for genus above.

Description. Shell ( Fig. 3 , Table 3): Dextral, flattened and depressed, umbilicus narrow and deep; 7.69–9.89 mm height, 15.40–18.62 mm width; whorls 5¼–5½, thin, glossy, slightly convex. Last whorl not descending in front, rounded at periphery. Colour pale brown and glass-like when fresh. Aperture large, ovately lunate, moderately oblique, with simple margin.

Body ( Fig. 2 ): Animal pale to dark brown, with broad right and left transparent shell lobes with many small white patches of pigmentation. Foot dark brown; sole tripartite, caudal foss and caudal horn well developed.

Radula ( Fig. 4 , Table 4): Subovate, comprises 25 transverse v-shaped rows of teeth; 17–137 teeth in each row. Central teeth meet at sharp angles in the middle line; all teeth unicuspid, spatulate.

Genital system ( Fig. 5 ): Genital organs chiefly occupy the anterior part of the body. Albumen gland (ag) of moderate size, slightly thickened, yellowish in colour, hermaphroditic duct (hd) tube slender, uterus (ut) very long, thick. Vas deferens (vd) a long and slender tube, entering apically to epiphallus. Epiphallus (e) a long slender tube, ephiphallic flagellum (ef) absent. Epiphallic retractor caecum (erc) shorter and thicker than epiphallus. Penis (p) short and stout, peanut-shaped. Gametolytic sac (gs) comprises three parts: gland with pointed appendage at distal end, slender tube at the middle and robust tube at the base. Vagina globose, yellowish colour. Free oviduct, long cylindrical, distal part short, orange colour. Amatorial organ absent.

Remarks. All six known taxa of the genus Sophina , namely S. calias , S. schistostelis , S. discoidalis , S. conjungens , and S. forabilis , are from eastern Myanmar (Blanford & Godwin- Austen, 1908). Most species are known only from their shell morphology, and the external body, genital system and radula have been studied in only S. calias and S. schistostelis by Stoliczka (1871) and Blanford & Godwin-Austen (1908), respectively. A comparison with S. calias ( Benson, 1859a) from Tenasserim Province, eastern Myanmar reveals that while their shell morphology and radula pattern are similar, their genital systems are different as explained under the remarks of the new genus description.

Figures

Fig.2.Aenigmatoconcha clivicola, new species, in natural habitat.A, living snail; B, foraging behavior.Photographs:Kitti Tanmuangpak.

Fig. 3. Aenigmatoconcha clivicola, new species, holotype (NHMSU-0013).

Fig. 4. Aenigmatoconcha clivicola, new species, radula of paratype (NHMSU-0014). A, whole radula; B, close up view of left side of radula; C, close up view of central part of radula; D, close up view of left latero-marginal teeth; E, close up view of central and first lateral teeth.

Fig. 5. Aenigmatoconcha clivicola, new species, genital system of paratype (NHMSU-0014) and schematic drawing. Abbreviations: ag, albumen gland; at, atrium; ep, epiphallus; erc, epiphallic retractor caecum; fo, free oviduct; gs, gametolytic sac; hd, hermaphroditic duct; p, penis; pr, penial retractor; pro, prostate gland; ut, uterus; v, vagina; vd, vas deferens. Photograph and illustration: Kitti Tanmuangpak.