taxonID	type	description	language	source
03D0E27C9B24FFEFC9F74081FC8CFE8E.taxon	type_taxon	Type species. Atopos semperi Simroth, 1891 by subsequent designation in Thiele (1931: 489).	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B24FFEFC9F74081FC8CFE8E.taxon	diagnosis	Diagnosis. The animal has an isosceles triangle cross-section and a short base (formed by the foot). Mid-dorsal region with more or less prominent mid-dorsal keel. Anterior body (about ⅓ of total length) thickest, gradually tapering to posterior end. Head with two pairs of tentacles: upper pair contractile and with dark eye spot on tip; lower pair short and bifid. Genitalia ditrematous: male pore opened behind right lower tentacle; female pore located near anal pore and pulmonary orifice in right pedal groove.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B24FFEFC9F74081FC8CFE8E.taxon	discussion	Remarks. Although Simroth gland (s) have been reported in Atopos, there have been no studies or direct observations, so its function is still being studied. However, Laidlaw (1940) and Barker (2001) hypothesised that it probably has a role in the copulatory process because it connects to the male genital organ and is close to the genital opening. At present, the genus Atopos comprises approximately 30 nominal species. They have a broad distribution, mainly being found in Southeast Asia, but have also been documented in Australia, Papua New Guinea, and India (Souleyet, 1852; Heynemann, 1876; Simroth, 1891, 1914, 1920; Sarasin & Sarasin, 1899; Babor, 1900; Collinge, 1902, 1903, 1908; Ghosh, 1912, 1913, 1915; De Wilde, 1984; Tan & Chan, 2009; Vermeulen & Liew, 2022). In Myanmar, A. gravelyi was the first and only species discovered in Kayin State (Ghosh, 1915). From this study, we identified one new species, named here as A. transversus, new species, from Shan State, and also documented a new record of A. laidlawi Collinge, 1902 from Tanintharyi Region.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFEFCB194201FC8CF8BE.taxon	diagnosis	Diagnosis. Upper part of mid-lateral line sepia, decorated with dark brown blotches and small spots. Lower part of mid-lateral line blue, decorated with slaty-black blotches and spots. Mid-lateral line with pale buff blotches above and dark-clove brown band below. Mid-dorsal keel rounded and prominent. Dark clove-brown mid-dorsal line. Foot pale yellow. Right Simroth gland well-developed with evaginable part long, cylindrical, and longer than penis; interconnected duct and secretory part indistinguishable with a long slender shape.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFEFCB194201FC8CF8BE.taxon	discussion	Remarks. Unfortunately, no new specimens identified to this species were collected, and the type specimen could not be located. Atopos gravelyi is superficially similar to Atopos maximus Collinge, 1903 from Thailand in terms of its colour pattern on the notum. However, A. gravelyi differs by possessing a prominent and dark clove-brown mid-dorsal line, pale buff blotches above and clove-brown band below the mid-lateral line, upper part of mid-lateral line sepia with dark brown blotches and spots, and lower part of mid-lateral line blue with slaty-black blotches and spots (Ghosh, 1915: pl. 16, fig. 1). In addition, A. gravelyi has only a right Simroth gland, with its evaginable part longer than penis length; interconnected duct and secretory part indistinguishable and long and slender in shape (Ghosh, 1915: pl. 19, fig. 27). In comparison, A. maximus possesses a yellowish-brown mid-dorsal line, a yellowish-brown band as the mid-lateral line with an irregular margin, slaty-blue mottling above the mid-lateral line, and a yellowish notum and decorated with scattered tiny black spots (Collinge, 1903: pl. 11, figs. 5, 6). Moreover, A. maximus has well-developed left and right Simroth glands, evaginable part short and about one-fourth of the penis length, thin interconnected duct, and secretory part a long cylindrical shape (Collinge, 1903: pl. 13, fig. 21). Therefore, we have retained this species as valid until new topotypic specimens as well as specimens from the other populations become available to verify the taxonomic status, intraspecific variation, and the relationship with A. maximus.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFE9CB2444F1FDC3FD0E.taxon	description	(Figs. 2, 4 A, B, 5 A – C)	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFE9CB2444F1FDC3FD0E.taxon	materials_examined	Material examined. One ethanol-preserved specimen (Fig. 2 A, B; length 21 mm, width and height 5 mm) (CUMZ 160201), Phra Cave (Site III), Ban Nam Yen, Tanintharyi Region, Myanmar, 11 ° 14 ′ 01.5 ″ N, 99 ° 10 ′ 42.8 ″ E. One ethanol-preserved specimen (Fig. 2 C, D; length 25 mm, width and height 5 mm) (CUMZ 160205), same locality as specimen CUMZ 160201.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFE9CB2444F1FDC3FD0E.taxon	diagnosis	Diagnosis. Upper part of mid-lateral line pale yellow; lower part pale brown and separated by irregular brown band. Mid-dorsal keel rounded and fairly prominent. Clear white mid-dorsal line flanked by brown stripes. Perinotum and foot off-white. Anterior and posterior ends of notum white. External characters. Preserved specimen (Fig. 2). Animal elongated elliptical, tapering at both ends, and anterior part thicker than posterior part. Dorsal side with fairly prominent mid-dorsal keel along its entire length. Notum rather smooth, and uniformly covered with small- to medium-sized and randomly scattered papillae. Papillae generally elliptical shaped and interconnected with rows of ridge (Fig. 4 A, B). Anterior and posterior ends of notum white. Notum pale yellowish, off-white to pale brown; mid-dorsal line white and flanked by irregular brownish stripes; mid-lateral line with a broad dark brown band and irregular margins. Upper and lower parts of mid-lateral line yellowish, and sometimes lower part with darker colour than upper part. Perinotum narrow with off-white sharp keel; foot (f) narrow and about half of body width (Figs. 2, 5 B). Anterior notum covers head region. Head and tentacles off-white; upper tentacles slightly long; lower tentacles short, stout, and bifid. Genital organs. Male genital pore located at base of lower right tentacle. Atrium short; penis (p) long cylindrical shape and situated at base of right body cavity. Vas deferens (vd) thin tube, originating at base of hermaphroditic-prostate gland complex, bound with oviduct before penetrating body wall on right side of foot, and then emerging from body wall near male genital pore and inserting near distal end of penis (Fig. 5 A, C). Penial retractor muscle (pr) inserted at distal end of penis. Simroth glands present on both sides: left Simroth gland (lsg) much smaller and less developed. Right Simroth gland (rsg) well-developed and consists of three parts: (i) evaginable part (es) is cylindrical and almost same length as penis; (ii) interconnected duct long, curled, and thin tube; and (iii) secretory part (sp) enlarged and long bulbous shape. Simroth gland retractor muscle (sr) attached at junction of interconnected duct and evaginable part (Fig. 5 C). Female genital pore (fg), anal pore (an), and pulmonary orifice (po) located around 4 to 6 mm from male genital pore in right pedal groove (Figs. 2 A, C, 5 B). Vagina (vg) short tubular duct. Receptaculum seminis (rs) club-shaped and situated at distal end of vagina. Oviduct (ov) long cylindrical tube. Albumen gland (ag), lobulated hermaphrodite gland (hg), and prostate gland (pg) bound together and undifferentiated (Fig. 5 A).	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFE9CB2444F1FDC3FD0E.taxon	distribution	Distribution. Atopos laidlawi is known from the type locality in southern Thailand (Collinge, 1902); the new record reported herein is from Tanintharyi Region, southern Myanmar. Comparative diagnosis. Atopos laidlawi can be distinguished from Atopos rugosus Collinge, 1902 and A. gravelyi by its fairly prominent mid-dorsal keel, mid-dorsal line white and flanked by irregular dark brown stripes, pale yellow and pale brown colours at upper and lower parts of mid-lateral line, respectively, and whitish anterior and posterior ends of notum. In comparison, A. rugosus possesses a well-developed mid-dorsal keel, yellowish-brown mid-dorsal line, notum dark green decorated with yellowish-brown spots, mid-lateral line absent, and anterior end of notum almost white (Collinge, 1902: pl. 5, figs. 46 – 48). In contrast, A. gravelyi possesses a prominent mid-dorsal keel, dark clove-brown mid-dorsal line, mid-lateral line with pale buff blotches above and clove-brown band below, upper part of mid-lateral line sepia with dark brown blotches and small spots, and lower part of mid-lateral line blue with slaty-black blotches and spots (Ghosh, 1915: pl. 16, fig. 1). Regarding the genitalia, A. laidlawi has both left and right Simroth glands and an enlarged bulbous secretory part (Fig. 5 C), while A. gravelyi possesses only the right Simroth gland and a very slender secretory part (Ghosh, 1915: pl. 19, fig. 27).	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B27FFE9CB2444F1FDC3FD0E.taxon	discussion	Remarks. Atopos laidlawi was described based on specimens collected during the ‘ Skeat Expedition’ in southern Thailand with only a brief description of external morphology (Collinge, 1902). However, the record from Luang Phrabang Province, Laos (see Inkhavilay et al., 2019: figs. 19 a, 55 a) seemed to differ from the typical by having no off-white colour at the anterior and posterior ends of the notum. The Laotian specimen has a sharp mid-dorsal keel, light brown mid-dorsal line, yellowish-brown notum with tiny black spots, irregular yellowish-brown mid-lateral line, and brown mottling on upper mid-lateral line, which suggest it is more likely to be A. maximus than A. laidlawi.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B21FFE5CB2B4181FDF5FB4E.taxon	description	(Figs. 3, 4 C, D, 5 D)	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B21FFE5CB2B4181FDF5FB4E.taxon	materials_examined	Type materials. Holotype: One ethanol-preserved specimen (Fig. 3 A, B; length 33 mm, width and height 5 mm) (CUMZ 160202), in a forest among the limestone hills at Montawa Cave, Taunggyi District, Shan State, Myanmar, 20 ° 45 ′ 16.8 ″ N 97 ° 01 ′ 03.4 ″ E. Paratypes: One ethanol-preserved specimen (Fig. 3 C; length 27 mm, width 6 mm, height 5 mm) (CUMZ 160203), same locality as the holotype. One ethanol-preserved specimen (Fig. 3 D; length 45 mm, width 8 mm, height 9 mm) (CUMZ 160204), Myin Ma Hti Cave (Pagoda), Kalaw Township, Taunggyi District, Shan State, Myanmar, 20 ° 35 ′ 56.3 ″ N 96 ° 36 ′ 36.9 ″ E.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B21FFE5CB2B4181FDF5FB4E.taxon	etymology	Etymology. The specific name ‘ transversus ’ is from the Latin words ‘ trans’ meaning across or cross, and ‘ versus’ means stripe or line; these refer to the presence of the crossed stripes on its dorsal side.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B21FFE5CB2B4181FDF5FB4E.taxon	diagnosis	Diagnosis. Notum yellowish-brown to pale brown with blackish to brownish cross-reticulated stripes without a distinct pattern. Mid-dorsal keel fairly prominent. Light brown mid-dorsal line with scattered tiny blackish spots. Perinotum and foot pale yellow to off-white. Anterior end with small whitish patch. External characters. Preserved specimen (Fig. 3). Animal narrowly elongated cylindrical and tapering to both ends. Dorsal side with fairly prominent mid-dorsal keel along its entire length. Notum rather smooth, and surface with a uniformly low cluster of small- to medium-sized and randomly scattered papillae. Papillae generally rounded, roughened surfaces and with an area of depressions at the centre (Fig. 4 C, D). Anterior end of notum with a small whitish patch. Notum yellowish-brown to pale brown with scattered tiny blackish spots; mid-dorsal line a lighter colour than notum; mid-lateral line absent. Lateral surface of body with irregular and scattered blackish to brownish streaks; sometimes with cross-reticulated stripes. Perinotum narrow with off-white to pale yellow sharp keel; foot narrow, about 2.5 - fold narrower than body width (Fig. 3). Anterior notum covers head region. Head and tentacles off-white; upper tentacle slightly short; lower tentacles short, stout, and bifid. Genital organs. Male genital pore located at base of lower right tentacle. Atrium long; penis (p) long cylindrical shape and situated at base of right body cavity. Vas deferens (vd) a thin tube, emerging from body wall near the male genital pore before inserting near distal end of penis. Penial retractor muscles (pr) inserted at distal end of penis. Simroth glands present on both sides; left Simroth gland (lsg) much smaller and less developed. Right Simroth gland (rsg) well-developed and consists of three parts: (i) evaginable part (es) is cylindrical shaped and slightly shorter than penis length; (ii) interconnected duct a short, thin, and curled tube; and (iii) secretory part (sp) is cylindrical shaped, curled, long, and slightly larger in diameter than interconnected duct. Simroth gland retractor muscle (sr) attached near distal end of evaginable part (Fig. 5 D). Female genital pore (fg), anal pore (an), and pulmonary orifice (po) located about 4 to 6 mm from male genital pore in right pedal groove (Fig. 3 A, C, D). Vagina short tubular duct; receptaculum seminis club-shaped; oviduct a coiled and cylindrical tube. Albumen gland (ag), hermaphrodite gland (hg), and prostate gland (pg) bound together and undifferentiable.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B21FFE5CB2B4181FDF5FB4E.taxon	distribution	Distribution. Atopos transversus, new species, is currently known only from the type locality in Shan State, Myanmar (Fig. 1). Comparative diagnosis. This new species can be distinguished from A. laidlawi and Atopos punctata Collinge, 1902 from Thailand, and A. gravelyi by having a fairly prominent mid-dorsal keel, light brown mid-dorsal line, yellowish-brown to pale brown notum with blackish to brownish cross-reticulated stripes in a random arrangement, and anterior end with a small whitish patch. In comparison, A. laidlawi possesses a fairly prominent mid-dorsal keel, white mid-dorsal line, broad dark brown and irregular margin mid-lateral line, and whitish anterior and posterior ends of notum. In contrast, A. punctata has a fairly prominent mid-dorsal keel, light yellow mid-dorsal line, and a yellow notum with scattered black spots (Collinge, 1902: pl. 5, figs. 49 – 52). Additionally, A. gravelyi possesses a prominent mid-dorsal keel, dark clove-brown mid-dorsal line, mid-lateral line with pale buff blotches above and clove-brown band below, upper part of mid-lateral line sepia with dark brown blotches and small spots, and lower part of mid-lateral line blue with slaty-black blotches and spots (Ghosh, 1915: pl. 16, fig. 1). In addition, A. transversus, new species, possesses both left and right Simroth glands with curled cylindrical secretory part (Fig. 5 D). In comparison, A. laidlawi has left and right Simroth glands with an enlarged bulbous secretory part (Fig. 5 C), while A. gravelyi possesses only the right Simroth gland with a very slender secretory part (Ghosh, 1915: pl. 19, fig. 27).	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
03D0E27C9B21FFE5CB2B4181FDF5FB4E.taxon	discussion	Remarks. Comparing specimens from the two localities, the notum and cross stripes of the new species have slightly different colours. Specimens from Montawa Cave (Fig. 3 A, C) possess a pale brown notum with brownish cross-reticulated stripes, whereas the specimen from Myin Ma Hti Cave (Pagoda) (Fig. 3 D) possesses a yellowish-brown notum with blackish cross-reticulated stripes, which we consider to be an intraspecific morphological variation.	en	Mitchueachart, Bowornluk, , Chirasak Sutcharit, Panha,, Somsak (2025): The slug genusAtopos Simroth, 1891 (Systellommatophora: Rathouisiidae) from Myanmar with description of a new species. Raffles Bulletin of Zoology 73: 43-53, DOI: 10.26107/RBZ-2025-0004
