Aenigmatoconcha Tumpeesuwan & Tumpeesuwan, 2017

Pholyotha, Arthit, Sutcharit, Chirasak, Tongkerd, Piyoros & Panha, Somsak, 2021, Systematic revision of the limestone karst-restricted land snail genus Aenigmatoconcha (Eupulmonata: Helicarionidae), with description of a new species, European Journal of Taxonomy 767, pp. 55-82 : 62-64

Genus Aenigmatoconcha Tumpeesuwan & Tumpeesuwan, 2017

Aenigmatoconcha Tumpeesuwan & Tumpeesuwan, 2017: 182–184 .

Aenigmatoconcha – Tumpeesuwan & Tumpeesuwan 2018: 171.

Type species

Aenigmatoconcha clivicola Tumpeesuwan & Tumpeesuwan, 2017 , by original designation.

Description

Shell dextral with 5–5½ convex whorls, strongly depressed to globosely depressed, medium-sized, thin to slightly solid, translucent, and pale milky to whitish-horny in colour. Shell surface smooth, glossy, and varix usually present. Body whorl well-rounded to slightly-shouldered. Suture shallow. Aperture slightly to very crescentic in shape with simple lip. Umbilicus open and deep.

Animal with reticulated skinand whitish, yellowish, pale fleshy grey to dark brown body with tiny whitish dots irregularly scattered over entire body. Mantle lobes well-developed (two shell lobes and three dorsal lobes; see Figs 3 , 5A ). Shell lobes can cover most, if not all of the shell and are retracted when disturbed. Left and right shell lobes very thin, translucent, ovate to triangular in shape; right shell lobe (rsl) smaller than left shell lobe (lsl). Dorsal lobes enlarged, crescent-shaped, covering body, and smaller than shell lobes. Anterior left dorsal lobe (ant-ldl) and posterior left dorsal lobe (post-ldl) smaller than right dorsal lobe (rdl). Sole tripartite, lateral foot margin, caudal fossa, and caudal horn present.

Genitalia with moderately long to very long penis, thick penial sheath, short to long epiphallus, small flagellum, and short vagina. Gametolytic organ with short gametolytic duct and bulbous gametolytic sac. Oviduct with large lobules; prostate gland running alongside oviduct.

Radular teeth arranged in anteriorly V-shaped or wide-angle U-shaped rows; central tooth symmetrical monocuspid and spatulate or oblong in shape; lateral and marginal teeth undifferentiated, asymmetrical monocuspid and spatulate or oblong in shape, and outermost teeth gradually reduced in size.

Distribution

Species of Aenigmatoconcha exhibit allopatric distributions and are restricted to limestone karsts in Thailand ( Fig. 1 ).

Figures

Fig. 3. Schematic drawing of living species of Aenigmatoconcha Tumpeesuwan & Tumpeesuwan, 2017, emphasizing the relative size, position and arrangement of mantle lobes (two shell lobes and three dorsal lobes).

Fig. 5. Genital system and mantle lobes of Aenigmatoconcha clivicola Tumpeesuwan & Tumpeesuwan, 2017, specimen CUMZ 7929 from the type locality. A. Mantle lobes. B. General view of genitalia; inset showing flagellum encircled with a loose tissue before clearing it out. C. Internal structure of penis. D. Internal structure of epiphallus and epiphallic caecum. White arrow indicates the junction between penis and epiphallus.

Fig. 1. Geographic distribution of four species of Aenigmatoconcha Tumpeesuwan & Tumpeesuwan, 2017 based on specimens examined herein.