Aenigmatoconcha sumonthai Tumpeesuwan & Tumpeesuwan 2018
Creators: name: Pholyotha, Arthit
name: Sutcharit, Chirasak
name: Tongkerd, Piyoros
name: Panha, Somsak
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Helicarionidae
Aenigmatoconcha
Aenigmatoconcha sumonthai

description: Aenigmatoconcha sumonthai Tumpeesuwan & Tumpeesuwan, 2018
Figs 1, 2C–E, 7A–D, 8, 10C
Aenigmatoconcha sumonthai Tumpeesuwan & Tumpeesuwan, 2018: 171–173, figs 2–6. Type locality: Tham Chang Phueak limestone range, Mueang District, Chumphon Province, southern Thailand.
Material examined
THAILAND • 45 sh, 20 sp; Chumphon Province, Mueang District, Limestone outcrops at Tham Chang Phuek Bureau of Monks; 10°26′50.0″ N, 99°02′07.1″ E; CUMZ 7922 • 40 sh; same collection data as for preceding; CUMZ 7923 • 18 sh, 10 sp; same collection data as for preceding; CUMZ 7937 • 45 sh, 6 sp; Chumphon Province, Mueang District, Limestone outcrops at Wat Tham Sanook; 10°28′51.3″ N, 99°04′28.3″ E; CUMZ 7924 • 10 sh, 7 sp; same collection data as for preceding; CUMZ 7925 • 22 sh, 11 sp; Chumphon Province, Sawi District, Limestone outcrops at Tham Nam Lod Thepnimit Bureau of Monks; 10°22′39.5″ N, 99°00′39.5″ E; CUMZ 7927 • 4 sh, 8 sp; Chumphon Province, Sawi District, Limestone outcrops at Wat Nam Cha; 10°17′57.0″ N, 99°01′58.5″ E; CUMZ 7926.
Description
SHELL (Fig. 7A–B). Shell strongly depressed to depressed, medium-sized (width 14.4–16.6 mm, height 7.0– 8.2 mm), thin, translucent, whitish colour, well-rounded to slightly shouldered body whorl, elevated spire, impressed suture, obvious varix, and open umbilicus.
EXTERNAL FEATURES (Fig. 2C–E). Animal with five well-developed mantle lobes. Left and right shell lobes pale yellowish to fleshy-grey colour, usually with black margin, and with or without small to large black spots or blotches. Three dorsal lobes crescent-shaped and smaller than the other two shell lobes. Black stripes behind long tentacles.
GENITALIA (Fig. 8). Atrium (at) enlarged and very short. Penis (p) long, cylindrical with thick penial sheath (ps) extending to half of penis length. Inner sculpture of penis with small conical penial pilasters (pp). Epiphallus (e1 + e2) as long as penis: e1 slender, and e2 bulbous. Inner sculpture of e1 with small thin longitudinal folds, while e2 with small papillae arranged in oblique rows. Epiphallic caecum (ec) short with thin penial retractor muscle (prm) attached at tip. Flagellum (fl) small and short.
RADULA (Fig. 10C). Teeth arranged in anteriorly V-shaped rows with half row consisting of about 63– 65 teeth at the middle plate. All teeth monocuspid and spatulate-shaped with curved cusp.
Distribution
Aenigmatoconcha sumonthai has a narrow distribution, with populations living on a few limestone hills in Chumphon Province (Fig. 1). We extended our survey, especially among limestone sites about 200 km southwards down to southern peninsular Thailand, but we could not find this species elsewhere.
Remarks
The lack of a penial sheath and flagellum in the male reproductive organs of A. sumonthai was originally reported to be similar to A. clivicola (Tumpeesuwan & Tumpeesuwan, 2018: 174, fig. 6). In this study, based on topotypic specimens, however, A. sumonthai was found to have a large and thickened penial sheath and small flagellum encircled with loose tissue (Fig. 8).
Aenigmatoconcha sumonthai shows variation in the black blotches on both shell lobes ranging from absent (Fig. 2E) to the lobes almost entirely covered (Fig. 2C). The DNA sequence analysis suggested that these variations formed a clade of A. sumonthai (Fig. 2). In addition, this species develops a calcareous epiphragm with a small perforation to limit body-water evaporation but allowing respiratory gas exchange during dormancy (Fig. 7C, D).
description: Published as part of 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, pp. 55-82 in European Journal of Taxonomy 767 on pages 70-72, DOI: 10.5852/ejt.2021.767.1487, http://zenodo.org/record/5528134