Hemiplecta funerea (Smith, 1896)

Sutcharit, Chirasak & Panha, Somsak, 2021, Systematic review of the dextral Hemiplecta Albers, 1850 (Eupulmonata, Ariophantidae) from Thailand with description of a new species and list of all the Indochinese species, ZooKeys 1047, pp. 101-154 : 101

publication ID	https://dx.doi.org/10.3897/zookeys.1047.65735
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scientific name	Hemiplecta funerea (Smith, 1896)
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Figures 1D, E View Figure 1 , 5A, B View Figure 5 , 6 View Figure 6 , 10F, G View Figure 10

Nanina distincta var. funerea Smith, 1896: 128. Type Locality: Vanbu, Tonkin [Van Ban District, Lao Cai Province, Vietnam]. Fischer and Dautzenberg 1904: 393.

Nanina distincta var. pallidior Smith, 1896: 128. Type Locality: Vanbu, Tonkin [Van Ban District, Lao Cai Province, Vietnam]. Fischer and Dautzenberg 1904: 393.

Hemiplecta funerea : Inkhavilay et al. 2019: 76, 77, figs 35f, 36a.

Type specimen.

See the species list of Indochinese species (Fig. 12B View Figure 12 ).

Material examined.

Thailand: Bor Klue District, Nan: CUMZ 4649 (5 shells). Ton Tong Waterfall, Doi Phu Ka National Park , Nan: CUMZ 4575 (8 specimens in ethanol; Figs 1D, E View Figure 1 , 5A, B View Figure 5 ), CUMZ 4576 (8 shells) .

Shell. Shell large (height up to 35 mm, width up to 55 mm), depressed conic, dextral, with 6-7 whorls; spire slightly elevated with wide and shallow suture. Shell almost black to dark brown with thin yellowish peripheral band. Apex obtuse; embryonic shell large with smooth surface; subsequent whorls with thin growth lines and thin radial wrinkles. Last whorl keeled; aperture large and ovate; lip simple, yellowish to dark yellow, and slightly thickened in adult snail. Columella slightly dilated; parietal callus thin and transparent. Umbilicus wide and deep (Fig. 5A, B View Figure 5 ).

Genitalia. Both male and female genital characters similar to that of H. humphreysiana . Gametolytic sac (gs) elongate with undifferentiated duct. The unique characters are a coiled epiphallic caecum (ec) and curved flagellum (fl), which are not found in the other species (Fig. 6A View Figure 6 ). Internally, penial sculpture (ps) consists of scattered papillary knobs lining penial wall; penial verge absent (Fig. 6B View Figure 6 ). Internal wall of vagina and internal structure of dart apparatus are similar to that in H. humphreysiana (Fig. 6C, D View Figure 6 ).

Radula. Each row contains about 286 teeth (140-(65-75)-1-(65-75)-135). Central tooth unicuspid conic-shaped, and dull cusp (Fig. 10F View Figure 10 ). Lateral teeth unicuspid, elongate, and slanted with pointed tip. Outer lateral teeth unicuspid, elongate; latero-marginal transition starts from tooth numbers 65 to 75. Marginal teeth slightly curved, bicuspid; endocone and ectocones small and of similar size (Fig. 10G View Figure 10 ).

External features. Living snails with long, black eye tentacles (Fig. 1D, E View Figure 1 ). Skin reticulated, pale brownish to brownish with dark reticulation across the entire head and foot above the lateral margin. Foot sole, caudal foss (Fig. 6G View Figure 6 ), caudal horn, and pedal groove similar to those in H. humphreysiana . Mantle edge, dorsal lobe, and shell lobe similar to those in H. humphreysiana , but only long and finger-shaped right shell lobe (rsl) present (Fig. 6E, F View Figure 6 ).

Distribution.

Previously recorded from the type locality in northern Vietnam, and several localities in northern and central Laos ( Smith 1896; Fischer and Dautzenberg 1904; Inkhavilay et al. 2019). Recently, we recorded this species from two localities in Nan Province, northern Thailand.

Remarks.

Smith (1896: 128) introduced two nominal subspecies of H. distincta from northern Vietnam, which were distinguished on the basis of shell color. The " Hemiplecta distincta var. funerea " has a purplish-black tinted shell (Fig. 5B View Figure 5 ), while the " Hemiplecta distincta var. pallidior " possesses a yellowish or olive-yellow shell (Fig. 5A View Figure 5 ). Since then, no new specimens of these two color forms have been critically examined or their status verified. We have collected both living snails and empty shells of these two forms in recent surveys in Laos and Thailand. The two forms are anatomically and genetically identical, and occur syntopically, and thus, in our judgement, are examples of different shell colors of the same species. We recognize H. funerea as a distinct and valid species, and treat Nanina distincta var. pallidior Smith, 1896 as its junior synonym (ICZN 1999: Art. 24, 74).

Hemiplecta funerea can be distinguished from H. distincta by the angulated, dark brown or yellowish shell, distinct penial sculpture, and a long and distinctively coiled epiphallic caecum (Fig. 6A View Figure 6 ) compared to the short and straight epiphallic caecum in H. distincta (Fig. 4A View Figure 4 ). The blackish reticulated skin on a yellowish background and blackish eye tentacles contrast with the greyish body in H. distincta (Fig. 1B-E View Figure 1 ).