Landouria bella Nahok & Chanlabut & Tumpeesuwan & Tumpeesuwan 2024, sp. nov.
Creators: name: Nahok, Benchawan
name: Chanlabut, Utain
name: Tumpeesuwan, Sakboworn
name: Tumpeesuwan, Chanidaporn
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Camaenidae
Landouria
Landouria bella

description: Landouria bella Nahok & S. Tumpeesuwan sp. nov.
Figs 2, 3, 4, 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), 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, 3, 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) 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.
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) 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). 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). 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). Vas deferens a thin, cylindrical tube, laterally entering epiphallus. Vagina short, distally globularly dilated, internally with five thick, longitudinal pilasters (Fig. 3 D). 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). 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) and gradually change from bicuspid to tricuspid; endocone small; mesocone large, lanceolate; ectocone triangular, with 2–4 tiny cusps (Fig. 4 D).
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).
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). 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). Most radular characteristics are quite similar to those of other species, except for the central tooth, which is lanceolate (Fig. 4 B).
description: Published as part of 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, pp. 347-362 in ZooKeys 1208 on pages 347-362, DOI: 10.3897/zookeys.1208.117056