Landouria bella Nahok & S. Tumpeesuwan, 2024

Nahok, Benchawan, Chanlabut, Utain, Tumpeesuwan, Sakboworn & Tumpeesuwan, Chanidaporn, 2024, Two new species of Landouria Godwin-Austen, 1918 (Gastropoda, Camaenidae) from Thailand, with a key to Thai species, ZooKeys 1208, pp. 347-362 : 347-362

publication ID	https://doi.org/ 10.3897/zookeys.1208.117056
publication LSID	lsid:zoobank.org:pub:ECCF2630-D984-45A8-BF19-DA219F26D495
DOI	https://doi.org/10.5281/zenodo.13224940
persistent identifier	https://treatment.plazi.org/id/DDCCEAB2-071E-4EB0-83D4-077CF7EE0232
taxon LSID	lsid:zoobank.org:act:DDCCEAB2-071E-4EB0-83D4-077CF7EE0232
treatment provided by	ZooKeys by Pensoft
scientific name	Landouria bella Nahok & S. Tumpeesuwan
status	sp. nov.

Treatment

Landouria bella Nahok & S. Tumpeesuwan sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , Table 1 View Table 1

Landouria sp. 16 — Nahok 2020: 61; fig. 24 G, I, table 3

Landouria sp. — Chanlabut and Nahok 2022: figs 2 D, 3 D, table 1

Type locality.

Thailand, Ratchaburi Province, Mueang Ratchaburi District, Khao Bin Cave, 13 ° 35 ' 37.56 " N, 99 ° 39 ' 56.57 " E, Isolated limestone hills, alt. 116 m. 7 July 2018. Benchawan Nahok and Utain Chanlabut leg.

Type specimens.

Holotype: • NHMSU -00056 (Fig. 2 A View Figure 2 ), 1 shell, SH = 8.0 mm, SW = 11.1 mm, AH = 4.3 mm, AW = 4.3 mm, UW = 3.3 mm . Paratypes: • NHMSU -00057 (Figs 2 B View Figure 2 , 3 View Figure 3 , 4 View Figure 4 ) 27 shells , • ZMCRU -0001 11 shells , • ZCPRU -0041 65 shells , • ZCPRU -0042 5 living specimens preserved in ethanol, same leg. and locality as holotype, 27 June 2020 . Other locality: • NHMSU -00058 (Fig. 2 C, D View Figure 2 ) 4 shells , • ZCPRU -0043 7 shells. Thailand, Phetchaburi Province, Cha-am District, Khao Nang Panthurat Forest Park , 12 ° 50 ' 20.27 " N, 99 ° 57 ' 6.88 " E, Isolated limestone hills, alt. 42 m. 13 Aug. 2017 and 7 July 2018. Benchawan Nahok and Utain Chanlabut leg. GoogleMaps

Diagnosis.

Shell small, depressed-globose. Body whorl rounded; aperture slightly oval, oblique, with thick, slightly reflected lip. Thin, small lamella present on inner columellar side of aperture. Flagellum large, cylindrical, with bent tip; penis short, small, cylindrical; vagina and free oviduct short, swollen. Basal part of gametolytic sac swollen.

Description.

(empty shells = 115, living specimens = 5). Shell (Fig. 2 View Figure 2 ) dextral, small, depressed-globose; body whorl large, well rounded. Whorls six; suture deep; apex obtuse; spire much elevated. Protoconch smooth; teleoconch with fine, irregular wrinkles, without scaly processes, last whorl with indistinct, incised spiral lines; umbilical side of last whorl with spiral lines more distinct. Umbilicus deep, very wide. Shell dimensions of specimens from type locality (N = 104; mean values in parentheses): shell height 5.7–9.4 mm (6.69 ± 0.71 mm), shell width 8.5–12.2 mm (10.54 ± 0.65 mm), aperture height 3.2–5.3 mm (4.47 ± 0.38 mm), aperture width 2.9–5.1 mm (4.08 ± 0.34 mm), and umbilicus width 2.7–5.4 mm (3.60 ± 0.33 mm). Shell dimensions of specimens from Khao Nang Panthurat (N = 11): shell height 5.81–7.09 mm (6.45 ± 0.64 mm), shell width 9.59–10.87 mm (10.23 ± 0.64 mm), aperture height 4.13–4.73 mm (4.43 ± 0.30 mm), aperture width 3.64–4.38 mm (4.01 ± 0.37 mm), and umbilicus width 3.25–3.83 mm (3.54 ± 0.29 mm).

Genital system (N = 3) (Fig. 3 View Figure 3 ). Atrium short. Penis small, cylindrical, shorter than flagellum, internally with four smooth, longitudinal pilasters, which gradually become corrugated at distal part close to verge. Verge short, swollen (Fig. 3 B View Figure 3 ). Penial retractor muscle present. Proximal part of epiphallus (ep 1) approximately equal to length of penis and vagina combined, but thicker and larger than penis. Distal part of epiphallus (ep 2) extremely short. Flagellum apically joins epiphallus, more than twice as long as penis, regularly long-cylindrical, bent at distal end, internally with three smooth, longitudinal pilasters (Fig. 3 C View Figure 3 ). Vas deferens a thin, cylindrical tube, laterally entering epiphallus. Vagina short, distally globularly dilated, internally with five thick, longitudinal pilasters (Fig. 3 D View Figure 3 ). Free oviduct shorter than vagina. Proximal part of gametolytic sac very stout, swollen, with a long, narrow, cylindrical tube, and with at its distal end sac-like, small, swollen, and spherical. Prostate gland very long; uterus long, swollen.

Radula (N = 3) Comprises 103–107 transverse rows with 63–71 teeth per row; radular formula: (22–24) + (6–8) + 1 + (6–8) + (22–24). Central tooth usually symmetric, unicuspid, lanceolate (Fig. 4 B View Figure 4 ). Lateral teeth quite like central tooth, but oblique, larger, and longer. Teeth on both sides begin to transform into indistinct bicuspid marginal teeth with tiny ectocone at tooth number 6–8 (Fig. 4 C View Figure 4 ) and gradually change from bicuspid to tricuspid; endocone small; mesocone large, lanceolate; ectocone triangular, with 2–4 tiny cusps (Fig. 4 D View Figure 4 ).

Etymology.

Specific epithet “ bella ” is derived from the Latin word “ bellus ”, which means lovely fine, pretty, and beauty. This name refers to the lovely shell of the new species.

Habitat.

This species inhabits isolated limestone hills, where it lives on rocks and the ground in a natural forest at the foot of limestone cliffs.

Distribution.

Landouria bella sp. nov. is currently known only from Khao Bin Cave, Ratchaburi Province, and Khao Nang Panthurat Forest Park, Phetchaburi Province, in western Thailand (Fig. 1 View Figure 1 ).

Remarks.

The new species is distinguished from other species of Landouria in Thailand by its depressed-globose shell, the presence of a thin, small columellar lamella on the inner side of the aperture, and the absence of an angular and peripheral keel (Fig. 2 View Figure 2 ). Its genital system is distinguished by its flagellum, which is regularly cylindrical, with a bent tip. The internal structure of the penis has a rounded swollen verge and resembles that of L. circinata , as well as L. tuberculata from Loei, L. chloritoides from Khon Kaen, and L. diplogramma from Nakhon Ratchasima, northeastern Thailand, but the new species differs in having the proximal part of the penis with thin longitudinal pilasters and the distal part which becomes gradually corrugated (Fig. 3 B View Figure 3 ). Most radular characteristics are quite similar to those of other species, except for the central tooth, which is lanceolate (Fig. 4 B View Figure 4 ).