Taxonomic review of the tree snail genus Amphidromus Albers , 1850 ( Pulmonata : Camaenidae ) in Laos , with the description of two new species

The land snail genus Amphidromus Albers, 1850 and its subgenus Syndromus Pilsbry, 1900 (family Camaenidae) in Laos are revised. Fourteen species from various habitats of deciduous forest and limestone areas throughout Laos are confirmed. The classification is revised and discussed, based on material examined from Laos, Cambodia, Vietnam and Thailand and after comparison with the type specimens in many museums. Two new species, A. (Amphidromus) syndromoideus Inkhavilay & Panha sp. nov., from central Laos, and A. (Syndromus) xiengkhaungensis Inkhavilay & Panha sp. nov., from northern Laos, are described and discussed.


Introduction
The Camaenidae family is comprised of some of the most fascinating land snails, and they occur in various habitat types in Southeast Asia.Many genera are ground dwellers but some are considered to be tree dwellers or arboreal snails, including those in the genus Amphidromus Albers, 1850.Members of Amphidromus have a conical shell (dextral and/or sinistral) and are very diverse in their shell color and banding patterns (Pilsbry 1900;Laidlaw & Solem 1961;Sutcharit & Panha 2006).Their distribution ranges from Assam in India to Indochina and to Sundaland, south of the Philippines, Wallacea, and a single species found in the Northern Territory of Australia (Solem 1959(Solem , 1983;;Laidlaw & Solem 1961).There are about 95 recognized species, which are classified in two subgenera (Thach 2014(Thach , 2015;;Thach & Huber 2014;Sutcharit et al. 2015 and references therein;Vermeulen et al. 2015).The nominotypical subgenus usually has a larger shell, is chirally dimorphic and has a long epiphallus and flagellum, whereas the smaller shells of the subgenus Syndromus Pilsbry, 1900

R e s e a r c h a r t i c l e
urn:lsid:zoobank.org:pub:FDFA7FAC-FC92-404B-9058-A426DAB6C693

Material and methods
Empty shells and living specimens were collected throughout Laos from different elevations above mean sea level (amsl) and forest types and also from fruit orchards.Living specimens were photographed before preservation, initially at -20°C and subsequently in 95% (v/v) ethanol, prior to conducting the anatomical study.Genital morphology was critically examined.Intact adult shells were measured for whorl number, shell height (h) and major diameter or shell width (d) using digital Vernier calipers (Mitutoyo, CD-6 CS).The buccal masses were removed and soaked in 10% (w/v) potassium hydroxide solution for 3-5 hours before extracting the radula, which was then cleaned in distilled water and preserved in 95% (v/v) ethanol.Radulae were examined by scanning electron microscopy (SEM: JEOL, JSM-5410 LV), recording the formula and shape of the teeth.
The type locality is mentioned from the original publication in the original wording and language.If possible, the modern name and/or regional names of the type locality are provided in square brackets.

Abbreviations
The terms proximal and distal are used for the region closest to and furthest away from the genital orifice, respectively.New abbreviations are introduced for the vaginal stimulator pilaster (vsp) and vaginal pouch (vpo), but all others are as defined by Solem (1983) and Sutcharit & Panha (2006):

Type species
Helix perversus Linnaeus, 1758 by subsequent designation of E. von Martens in Albers (1860).

Description
Shell chirally dimorphic, elongate to ovate conical, rather thin and glossy.Spire conical; apex acute, light brown and without black spot on tip.Whorls 6 to 7 nearly smooth; suture wide and depressed; last whorl rounded.Periostracum usually deciduous to yellowish-green radial streaks, more conspicuous on last whorl and faded in previous whorls.Last whorl processes thin, whitish subsutural band, sometimes with one or two reddish-brown spiral bands below periphery but usually not reaching lip; varix absent.Parietal callus thin and transparent.Aperture ovate to elongate; peristome expanded and not reflected; lip usually purplish-pink or white.Columella straight, thickened, purplish-pink or white.Umbilicus narrowly opened.

Genital organs
Atrium (at) rather short (n = 10).Penis (p) long and stout.Epiphallus (e) long, about two times as long as penis; flagellum (fl) longer than epiphallus and terminated in folded coil.Appendix very small, extends from folded coil of flagellum, about same length as epiphallus.Penial retractor muscle (pr) short, thickened and inserted distally on penis.Vas deferens (vd) narrow tube connecting epiphallus and free oviduct (Fig. 6A).
Internal penial wall corrugated into series of thick penial pilasters (pp), which form a fringe around penial verge.Penial verge (pv) rather long and curved, conical, with smooth surface and orifice located at tip (Fig. 6B).
Vagina cylindrical, about two times as long as penis.Gametolytic duct very long, proximal to genital orifice large, coiled; distal to genital orifice tapering to small tube, short, about one-third length of proximal part and connected to enlarged gametolytic sac.Oviduct and albumin gland small (Fig. 6A).

Distribution
This species is distributed widely, from many localities in central and northern Laos.There are also records from Nan Province, Thailand and Phong Nha National Park, Vietnam.

Remarks
Amphidromus roseolabiatus differs from A. smithi Fulton, 1896and A. ventrosulus Möllendorff, 1900(Zilch 1953;Sutcharit et al. 2015) in having an enantiomorphic shell coiling, purplish-pink lip and fine green streaks.In contrast, A. smithi has a sinistral shell, brownish lip with dark spot on the apex, and A. ventrosulus has a sinistral shell, uniform green color, elongate spire and more depressed suture.INKHAVILAY K. et al., Review and new species of Amphidromus in Laos Laidlaw & Solem (1961) recognized A. roseolabiatus as belonging to an uncertain subgenus that was probably close to the subgenus Syndromus.However, this species exhibits dimorphic shell coiling with a long flagellum and appendix, which are typical characters of the nominotypical subgenus (Fig. 6A).Two color forms were observed in the recently collected materials.The typical color form has a greenish radial streaked periostracum and pinkish apertural lip (Figs 2A, 4A-B).There are some specimens with the typical color form showing one or two additional reddish-brown lower, peripheral bands (Fig. 4B).The second, whitish form usually has a greenish periostracum, as in the typical color form, but a white apertural lip (Figs 2B, 4C-F).However, these two color forms have identical genital structures and sculptures inside the penis and vagina.Amphidromus (Amphidromus) laosianus Bavay, 1898 Figs

Remarks
Currently known only from the type locality.The unique shell characters are chirally dimorphic, conical to elongate conical; whorls weakly convex, with white subsutural band.Shell color with yellowishbrown or brownish radial streaks on pinkish to whitish ground color; dark varix present.Aperture elongated; peristome thickened, expanded and reflected; lip folded and pinkish.Parietal callus pinkish and thickened; columella pinkish and straight; umbilicus imperforated.Laidlaw & Solem (1961) mentioned that this species is similar to the A. atricallosus leucoxanthus variety "laidlawi" (Solem 1965: pl. 1, fig. 3;Sutcharit & Panha 2006: fig.4d-e).However, it differs in having a slender shell and pinkish peristome, parietal callus and inside of the aperture, while "var.laidlawi" has a white lip, parietal callus and inside aperture, and more depressed suture.Furthermore, A. cambojiensis (Reeve, 1860) can be distinguished from this species by having a very large and thickened shell, thickened and white parietal callus and lip, and purplish inside aperture (see Sutcharit et al. 2015).

Description
Shell chirally dimorphic, elongate conical, rather thick and glossy.Spire elongate conical; apex acute, with or without black spot on tip.Whorls 6 to 7 convex to smooth; suture wide and shallow; last whorl rounded to well rounded.Periostracum thin corneous; varix usually absent.Shell color varies from uniform white, yellowish to reddish brown or with narrow to wide brownish peripheral and umbilical bands.Parietal callus thin and transparent.Aperture ovate to oblique elongated; peristome expanded and not reflected; lip white, brownish or purplish.Columella straight, thick or thin and white or brownish.Umbilicus imperforated.

Remarks
This species tend to have a high diversity of shell colors, with eight infra-specific names being provisionally proposed to distinguish the distinct shell shape and color patterns.We examined all the type specimens and recognized them as subspecific entities of one species.Laidlaw & Solem (1961) recognized this species as a synonym of A. dautzenbergi Fulton, 1899.The latter species exhibits a thin shell, yellowish with a thin faded greenish streak near the umbilicus, a white subsutural band and an elongated ovate aperture, while A. pervariabilis has a thick shell, monochrome or with dark brown spiral band and ovate aperture.However, the type locality of A. dautzenbergi was "Tonkin", the historical political division during the French colonial period, and it still is an uncertain boundary.The species is known from the holotype only (Sutcharit et al. 2015: fig. 6g), no specimen was found in the present study, and, therefore, the taxonomic status of A. dautzenbergi and A. pervariabilis remains to be confirmed.Geret, 1912 Figs 1, 2C, 3C, 4I; Table 1 Amphidromus givenchyi Geret, 1912: 55-56

Remarks
The species description, as well as the morphology of the genitalia and the radula, have been carefully presented in Sutcharit & Panha (2006), which allows an unambiguous recognition of this species.The unique characters are a relatively medium sized (compared to other members of this genus, as shown in Table 1), ovate-conical and dextral shell; apex with black spot; aperture oblique; peristome expanded and not reflected; parietal callus thin and transparent to slightly thickened and white; shell color uniform greenish with pale to yellowish color on earlier whorl, and greenish subsutural band; genitalia contain long and slender penis, short and curved epiphallus of equal length to flagellum; proximal to enlarged and coiled appendix epiphallus; appendix short.
The early records of this species were from the Ubon Ratchathani and Kalasin Provinces of Thailand, and the Luang Phrabang and Savannakhet Provinces of Laos (Sutcharit & Panha 2006).Here, two more localities from Salavan Province, Laos are added.All of the records are from dry dipterocarp to deciduous forests with sandstone hills.The snails were found in small holes on branches or tree trunks during the aestivation period (Fig. 3C).

Remarks
No specimen was found in this survey.Amphidromus protania has a very similar shell shape to that the dipterocarp forest species A. givenchyi.The genitalia contain a long and coiled proximal part of the epiphallus, with a relatively short appendix, as in A. givenchyi (Lehmann & Maassen 2004;Sutcharit & Panha 2006).However, the characters distinguishing it from A. givenchyi are the relatively smaller shell (height 26-31 mm in A. protania; Table 1), the yellowish shell color as well as the brownish subsutural and spiral bands on the periphery.Moreover, Lehmann & Maassen (2004) mentioned that the brownish banding pattern had less variation.However, a brownish spiral band on the periphery can also be observed in juvenile A. givenchyi (see Sutcharit & Panha 2006: fig. 4o

Diagnosis
The new species differs from all other known Amphidromus (Syndromus) species in having a long epiphallus and flagellum and very long appendix, both being unique characters of the nominotypical subgenus (Solem 1983;Sutcharit & Panha 2006).The new species differs from A. roseolabiatus in having a small and thin shell, inconspicuous greenish radial streaks and about two times longer appendix.In contrast, A. roseolabiatus has a larger solid shell, conspicuously greenish radial streaks in fresh specimens, sometimes with a single brownish spiral band below the periphery, purplish-pink apertural lip, and a short appendix.

Etymology
The specific epithet 'syndromoideus' is from 'syndromus', an Amphidromus subgeneric name, and the suffix '-oideus', meaning 'like or resembling'.This name refers to the resemblance in shell morphology of the new species with members of the subgenus Syndromus.

Description
Shell chirally dimorphic, thin, rather small, elongate conical and glossy.Spire conical; apex acute, brownish and without black spot on tip.Whorls 5 to 6 weakly convex; suture depressed; last whorl rounded.Periostracum thin and transparent.Last whorl with narrow white subsutural band and shell color uniform yellowish with green radial streaks on last whorl (pale to inconspicuous in older whorls and empty shells); varix absent.Parietal callus thin and transparent.Aperture wide ovate; peristome weakly expanded; lip whitish or transparent.Columella straight, thickened and white.Umbilicus narrowly opened.

Genital organs
Atrium (at) rather short (n = 10).Penis (p) short and conic-shaped.Epiphallus (e) long, slender and two times longer than penis.Flagellum (fl) short, about half length of epiphallus and terminated in folded European Journal of Taxonomy 330: 1-40 (2017) coil.Appendix very long, small tube extends from folded coil of flagellum, about three times as long as epiphallus.Penial retractor muscle (pr) short, thickened and inserted distally on penis.Vas deferens (vd) narrow tube connecting epiphallus and free oviduct (Fig. 6C).
Vagina cylindrical, about four times as long as penis.Gametolytic duct very long, proximal to genital orifice large, coiled; distal to genital orifice tapering to small tube and connected to ovate gametolytic sac.Oviduct and albumin gland very small (Fig. 6C).

Distribution
This new species is currently known from the type locality only, a dry evergreen forest with limestone outcrops in the central part of Laos at Thakhek District, Khammouan Province.

Remarks
Two living snails were found during the aestivation period in a small tree hole a height of 5 m (Fig. 3D).

Diagnosis
Shells mostly sinistral, conical to elongate conical and rather small (height 25 to 40 mm), varices absent and varying in color pattern.Genital characteristics show camaenid type with short epiphallus and flagellum, appendix absent, vaginal pouch and vaginal stimulator pilaster sometimes present.Radula teeth with spatulate shape.
The subgenus Syndromus was first nominated as "Sinistral Division" for Amphidromus with a relatively smaller sinistral coiling shell (Pilsbry 1900).Until onw, the genital characters of the type species have never been examined; only Wiegmann (1894) briefly reported on the radular and jaw structures of the type species.To clarify the genitalia and radula characters of the subgenus, spirit preserved specimens in the Zoological Museum of Amsterdam (ZMA) collection were examined and are described below.Amphidromus (Syndromus) contrarius (Müller, 1774) Fig

Remarks
Approximately 45 species are currently recognized in this subgenus.Laidlaw & Solem (1961) divided those recognized species into six supraspecific groups based on geographic distribution.All of the Indochina forms (six species) were assembled into the A. xiengensis group (Group XIV).However, the members exhibit diverse shell color patterns.Their genital characters have not yet been described.Here, we attempt to clarify those described specific entities and color forms with distinct reproductive characters and shell banding pattern.
Most of the species of the subgenus Syndromus exhibit diverse shell banding, which can be characterized in terms of five banding systems.The definitions of those five bands and description of shell color forms follow the conventional procedures used in Euhadra (Pilsbry 1928), Cepaea (Cain & Sheppard 1950;Cain & Currey 1963), Partula (Murray & Clarke 1966), Theba pisana (see Cowie 1984) and Satsuma (Wu et al. 2008).The syndromid species complex maintains a polymorphic color pattern of varied width, shape and coloration.We simplify the banding pattern systems by modifying that outlined above INKHAVILAY K. et al., Review and new species of Amphidromus in Laos and dividing them into six sections or six banding systems (Fig. 8D), starting from the uppermost of the last whorl to the lowermost near the umbilicus.They are: Band 1 (subsutural band) just below or in contact with the suture, usually thin and sometimes omitted in some species or populations.Bands 2 and 3 (supra-peripheral bands) begin from below Band 1 to the posterior angle of aperture.These two bands are usually separated with a narrow gap in the middle.Band 2 is located just below Band 1, and Band 3 is placed above the posterior angle of the aperture.These two bands are usually modified as dotted, blotched or divided into several thinner bands.
Bands 4 and 5 (sub-peripheral bands) located below the posterior angle of the aperture or below the periphery of the umbilicus.These two bands are usually separated by a narrow to wide gap of ground color.Band 4 normally contacts the bottom of Band 3. Band 5 is located just around the umbilicus.

Description
Shell sinistral, elongate conical, rather small, thin and glossy.Spire conical; apex acute, with black spot on tip.Whorls 5 to 6 slightly convex; suture depressed; last whorl rounded.Periostracum transparent to thin corneous.Last whorl process, with yellow to absent Band 1; Bands 2 to 4 (sometimes Bands 2 to 5) usually merge and become brownish slanted blotches with flame shape; Band 6 yellowish or roseate.Parietal callus thin and transparent.Aperture auriform; peristome expanded to weakly expanded; lip white to transparent.Columella straight and white.Umbilicus narrowly opened.

INKHAVILAY K. et al., Review and new species of Amphidromus in Laos
Internal penial wall nearly smooth and corrugated into thin penial pilasters, which form fringe around penial verge.Penial verge rather small, conical, with smooth surface (Fig. 11B).
Vagina cylindrical, of about same length as penis.Gametolytic duct long, proximal to genital orifice, of larger diameter than vagina and coiled; distal to genital orifice tapering to small tube of about same length as proximal part and connected to gametolytic sac.Oviduct and albumin gland very small (Fig. 11A).(Pfeiffer, 1861) from Thad Fek, Attapeu, Laos showing the reproductive system and interior structures of the penis and vaginal chamber (CUMZ 7023).C-D.Amphidromus flavus (Pfeiffer, 1861) from Ban Na Deauy, Luang Phrabang, Laos showing the general characteristics of the genital system and the interior structures of the penis, atrium and vagina chamber (CUMZ 7027).
Internal wall of vagina shows longitudinal vaginal pilasters (vp); proximal to genital orifice with nearly smooth surface for about half of its length, distally pilasters become corrugated ridges (Fig. 11B).

Distribution
The species is known from southern Laos, where the specimens were collected at Thad Fek, Sammakeexay District, Attapue and Thad Phasoam, Paksong District, Champasak in a dry dipterocarp forest.

Description
Shell sinistral, small, ovate conical, small, thin and glossy.Spire conical; apex acute yellowish, with black spot on tip.Whorls 5 and 6 convex; suture depressed; last whorl rounded to well rounded.Periostracum transparent to thin corneous.Last whorl processes uniform yellowish; Bands 1 to 3 usually absent; Bands 4 and 5 absent or present with indistinct bands; Band 6 usually absent or sometimes present as scantly reddish band.Parietal callus thin and transparent.Aperture ovate to sub-ovate; peristome weakly thickened and shortly expanded; lip whitish.Columella straight and white.Umbilicus opened to narrowly opened.

Genital organs
Atrium (at) rather long (n = 5).Penis (p) long, cylindrical and enlarged from middle to end.Epiphallus (e) cylindrical, length longer than that of penis; flagellum (fl) short and one fourth as long as epiphallus; appendix absent.Penial retractor muscle (pr) thickened and relatively short.Vas deferens (vd) small tube, connecting epiphallus and free oviduct (Fig. 11C).
Internal penial wall corrugated into thin penial pilasters, which form fringe around penial verge.Penial verge conical, with smooth surface and orifice open near tip (Fig. 11D).
Vagina cylindrical, long, slender about two times as long as penis length.Gametolytic duct long, proximal to genital orifice almost same diameter as vagina, distally tapering; distal to genital orifice small tube of about same length as proximal part and connected to gametolytic sac.Oviduct and albumin gland small (Fig. 11C).

Distribution
The distribution range of the species is from Vientiane to Luang Phrabang Provinces.

Remarks
Amphidromus flavus differs from A. sinensis (Benson, 1851) in having a smaller shell, the spire more ovate and conical, with a single reddish band on the penultimate whorl.It can be distinguished from A. xiengensis in having a smaller shell, ovate conical, without any band on yellowish ground color or on shell sculpture.It differs from A. globonevilli Sutcharit & Panha, 2015 by having a larger shell size, and it is smaller than A. principalis Sutcharit & Panha, 2015. In comparison, A. globonevilli has an elongate conical shell and a faint yellow spiral band below the periphery, while A. principalis has a more elongate conical shell, last whorl without any band, aperture ovate.In our collection we found two types identified as A. flavus and A. flavus var."proxima", living sympatrically at Luang Phrabang and Vang Vieng.

Remarks
The type specimens have recently been figured in Sutcharit et al. (2015: fig.13e-f).The unique characters of this species are the sinistral, ovate conical shell; spire with a brownish color; last whorl well rounded.Shell whitish ground color, Bands 1 to 3 and 6 absent and Bands 4 and 5 perform reddish brown bands.Aperture ovate; peristome weakly expanded; lip white.
Amphidromus roemeri was described based on specimens collected by H. Mouhot with the type locality "Laos Mountains, Camboja".This collection locality is a historical geographic name with an uncertain boundary.So far, this species is known only from the type specimens and an uncertain record from Laos by Laidlaw & Solem (1960: 654).However, no specimens were found in the present study; therefore the records from Laos still remain to be confirmed.
Laidlaw & Solem (1961) placed A. roemeri as a junior synonym of A. sinensis (Benson, 1851) from S China.We have examined the type specimens of both species and found that A. roemeri differs from A. sinensis by having an ovate conical, whitish shell, aperture ovate, spire short and conical, last whorl well rounded (see Sutcharit et al. 2015: fig.13e-f).In contrast, A. sinensis (see Sutcharit et al. 2015: fig.16g-i) has a yellowish shell, elongate conical spire, aperture auriform and the last whorl rounded.Furthermore, A. globonevilli differs by having a larger, spired conical, yellowish shell and an oblique aperture.

Material examined
This species was described from specimens collected by A. Pavie from the L. Morlet collection.The original description includes an illustration of a single shell, one set of shell measurements, and a species description that may be based on one unknown specimen.There is a single specimen of L. Morlet in the MNHN collections, with an original label stating "Type".Fischer-Piette (1950: 153) wrote the "holotype, 35 mm", which we consider to be an inadvertent lectotype designation (ICZN 1999: Art.

Description
Shell sinistral, elongate conical, thickened and glossy.Spire conical; apex acute, with brown or black spot on tip.Whorls 6 to 7 slightly convex; suture depressed; last whorl rounded.Periostracum thin.Last whorl monochrome whitish, with black Band 1 and Bands 2 to 6 absent; spire with concurrent brownish blotches of Bands 2 and 3. Parietal callus thickened and transparent or white.Aperture subovate; peristome rather thickened, expanded and weakly reflected; lip whitish.Columella thickened, perpendicular and white.Umbilicus narrowly opened to perforate.

Remarks
Previous records of this species were from the type locality in Stung Treng Province in the north and Kampot and Sihanoukville Provinces in the south of Cambodia, and later from Srakeo Province, Thailand.Laidlaw & Solem (1961: 658) mentioned that the distribution range of this species was in Laos.However, no specimens were collected and, therefore, new records of this species in Laos are required to confirm its precise distribution.
Amphidromus semitessellatus can be distinguished from A. flavus and A. xiengensis by having a solid shell, with black Band 1, last whorl monochrome whitish, Bands 2 to 6 absent, and spire with concurrent brownish blotches of Bands 2 and 3.In comparison, A. flavus has a yellowish and thin shell, Bands 1 to 6 usually absent, but sometimes Bands 4 and 5 present and with scantly reddish Band 6.Meanwhile, A. xiengensis exhibits a yellowish ground color, thinner shell, reddish Band 1, Bands 2 and 3 with concurrent brownish slanted blotches, dark brown Bands 4 and 5, and yellowish or reddish Band 6.

Description
Shell sinistral, conical to elongate conical, rather thick and glossy.Spire conical; apex acute with brown or black spot on tip.Whorls 6 to 7 slightly convex; suture depressed; last whorl rounded.Periostracum thin and corneous.Last whorl with reddish to brown Band 1; Bands 2 and 3 as concurrent slanted brownish blotches continuous to expanded lip; Bands 4 and 5 with brownish spiral bands; Band 6 absent or yellowish to reddish.Parietal callus transparent or weakly thickened and white.Aperture subovate; peristome rather thick and expanded; lip whitish.Columella thickened, perpendicular and white.Umbilicus narrowly opened to perforated.

Genital organs
Atrium (at) somewhat short (n = 5).Penis (p) long, cylindrical and enlarged at middle.Epiphallus (e) cylindrical, two times as long as penis; flagellum (fl) short, one third as long as epiphallus; appendix INKHAVILAY K. et al., Review and new species of Amphidromus in Laos absent.Penial retractor muscle (pr) thickened and relatively short.Vas deferens (vd) small tube, connecting epiphallus and free oviduct (Fig. 14A).
Vagina cylindrical, long, slender, about 1.5 times as long as penis.Gametolytic duct long, proximal to genital orifice of same diameter as vagina and distally tapering; distal to genital orifice very small tube of about same length as proximal part and connected to gametolytic sac.Oviduct and albumin gland very large (Fig. 14A).
Internal wall of vagina shows longitudinal vaginal pilasters (vp); pilasters vary narrow and thin throughout vaginal length (Fig. 14B).

Distribution
The species is widely distributed and can be found in several habitats such as forests, fruit orchards and limestone areas between latitudes 14° and 16° N.

Remarks
Amphidromus xiengensis differs from A. areolatus and A. zebrinus in having a larger shell, reddish Band 1, concurrent slanted and brownish blotched Bands 2 and 3, and brownish spiral Bands 4 and 5.In contrast, the other two species have a smaller shell, Band 1 absent and Bands 2 and 3 merged and becoming brownish slanted blotches in A. zebrinus or brownish slanted blotches with a flame shape in A. areolatus.It differs from A. eudeli Ancey, 1897 (Fig. 13N, syntype RBINS 617427) and A. fuscolabris Möllendorff, 1898 (Fig. 13I, holotype SMF 7641) in having a white peristome, reddish Band 1, and Bands 2 and 3 usually separated.In comparison, A. fuscolabris shows a purplish-pink peristome, yellowish Band 1, Bands 2 to 5 merged and roseated Band 6, while A. eudeli exhibits a brownish lip, yellow color Band 1 and Bands 2 and 3 usually merged.
Two subspecific entities have been proposed; we, however, recognize them as a single biological species, A. xiengensis.

Remarks
Amphidromus fuscolabris differs from A. zebrinus and A. eudeli in having a large and elongate shell, apex tinted pink, purplish-pink parietal callus, Band 1 yellowish and Bands 2 to 5 merged and becoming 6 to 7 slanted blotches (on last whorl).In comparison, A. zebrinus (see Sutcharit et al. 2015: fig. 15k) has a smaller shell, Band 1 absent, Bands 2 and 5 merged and becoming fifteen narrow slanted stripes on last whorl, and reddish band in between Bands 5 and 6.On the other hand, A. eudeli (Fig. 13N, holotype RBINS 617427) has a smaller shell, thin parietal callus, Bands 2 and 3 merged and Bands 4 and 5 well developed.

Type material
The species description included two varieties, "var. A. viridis" and "var.B. varians", but only one set of shell measurements was given in the original description, of the nominotypical variety.The specimen SMF 7559, labelled as "var.A. viridis", exactly matches the dimensions given in the original description.Therefore, we believe this implied that the specimens of "var. A. viridis" pertain to the type series of A. haematostomus s.s.The specimen SMF 7559 (Fig. 13O) was designated as the lectotype in Zilch (1953: 132, pl. 22, fig. 4), which is considered to be a valid lectotype designation of the species, and the other specimen from the same lot becomes the paralectotype SMF 5760 (1 shell; Fig. 13P).

Remarks
This species is currently known from the type locality only.The shell characters are clearly distinct from all other recognized species.The shell is sinistral and ovate conical.Then apex is acute, with a black spot on the tip.The last whorl is rounded; the color of the shell is a monochrome greenish (faded in old specimen), and there are a yellowish subsutural band and an umbilical area.Then aperture is ovate; the peristome expanded and weakly reflected; the lip is reddish-purple.The parietal callus is reddish-purple and thickened; the columella is also reddish-purple and dilated; the umbilicus imperforated.Laidlaw & Solem (1961) suggested that this species was probably a junior synonym of A. roseolabiatus.However, after comparing the type specimens of both species and recently collected specimens of A. roseolabiatus, A. haematostoma clearly differs from it in having an ovate conical shape, uniform greenish to yellowish shell, yellowish subsutural and umbilical area, thickened parietal callus, lip widely expanded, and reddish-purple lip and parietal callus.Moreover, A. roseolabiatus exhibits an elongate conical shell, greenish radial streaks, white subsutural band, transparent parietal callus, and lip pinkish or white and expanded.Lehmann & Maassen (2004: 20) recorded the genital characters (without illustration) of the topotypic population and mentioned that it had a "very short flagellum and a short conical verge".These are the distinguishing characters of this subgenus.However, further investigation of the genitalia is necessary to confirm the subgeneric status.Inkhavilay & Panha sp. nov.urn:lsid:zoobank.org:act:7BA4B989-3003-4F09-94E5-F21B392BEA28Figs 1, 13S-T; Table 1 Diagnosis

Amphidromus (Syndromus) xiengkhaungensis
The new species is superficially similar to A. roemeri, but the distinguishing characters are a relatively large and thick shell, dark to brownish spire, Bands 2 and 3 merged and become tinted pink stained, with a pale tinted pink lip.In contrast, A. roemeri shows a relatively small and thin shell, whitish ground color, Bands 2 and 3 absent, and has a white lip.Amphidromus xiengkhaungensis sp.nov.differs from A. sinensis and A. flavus by having an ovated conic shell, Bands 2 and 3 stained with tinted pink, ovate aperture and slightly angular last whorl.In comparison, A. sinensis and A. flavus have an elongate conical, relatively small and thin shell, with a yellowish color and rounded last whorl.In addition, A. globonevilli differs from this new species by having a small and thin shell, with a yellowish color, last whorl rounded and Bands 2 and 3 absent.

Etymology
The specific epithet 'xiengkhaungensis' refers to the type locality of the new species.

Description
Shell sinistral, ovate conical, rather thick and glossy.Apex acute, color tinted pink; spire conical with dark color; suture wide and depressed.Whorls 5 and 6 nearly smooth; last whorl slightly angular.Periostracum thin, corneous and transparent.Earlier whorls with darker color; varix absent.Shell banding without Band 1; Bands 2 and 3 merged and becoming tinted pink stained; Bands 4 and 5 dark brown; Band 6 absent.Parietal callus thin and transparent to slightly thick and white.Aperture ovate; peristome expanded and weakly thickened; lip pale tinted pink to white.Columella straight, thickend and white.Umbilicus narrowly opened.

Remarks
Amphidromus xiengkhaungensis sp.nov. is currently known from the type locality only, a dry green forest and isolated limestone forest surrounded by a reservoir and agricultural areas.The empty shells were found on the floor among the leaf litter.Unfortunately, no living specimens have been collected.

Discussion
The first species of Amphidromus from Laos, A. roemeri, was described by Pfeiffer (1863a).Subsequently, A. xiengensis, A. laosianus and A. haematostoma were reported by Morlet (1891), Bavay (1898) and Möllendorff (1898), and the latest described species was A. protania by Lehmann & Maassen (2004), collected from Ban Donxé, Salavan Province.However, there are many species for which basic information is still unclear, such as the type locality for, e.g., A. roemeri, where the author stated only "Laos Mountains" as the locality.Almost all records were from southern areas or lowlands, except for A. xiengensis, which was recorded in the north (Fig. 1).
In this paper we describe two new species, both known from their type localities only.Amphidromus syndromoideus sp.nov.has a small shell size, dextral and sinistral, green color with long epiphallus and flagellum, and very long appendix.Amphidromus xienkhaungensis sp.nov. is described based on shells only.The shell is superficially similar to that of A. roemeri, but it is larger and thicker, with a dark to brown spire.Moreover, the two recorded species Amphidromus xiengensis and A. flavus were described here using shells and genital anatomy.
In the southern part of Laos we collected the four species A. givenchyi, A. fuscolabris, A. areolatus and A. xiengensis.The most dominant species were A. givenchyi, A. fuscolabris and A. areolatus, which could be found between the altitudes of 140 and 190 m amsl.Only two species were collected in the central region of Laos, A. roseolabiatus and A. syndromoideus sp.nov., with the most dominant species being A. roseolabiatus.In the northern part of Laos we collected five species of Amphidromus; surprisingly A. roseolabiatus and A. xiengensis were found in both southern and northern Laos, but A. flavus, A. pervariabilis and A. xiengkhuangensis sp.nov.were only found in northern Laos, from Vang Viang to Phongsaly.
Amphidromus roseolabiatus and A. xiengensis were the most dominant and widely distributed species throughout Laos.They can be found in several habitats, even in limestone areas from the south to the north.However, A. givenchyi, A. syndromoideus sp.nov.and A. xiengkhaungensis sp.nov.were specific to their unique habitats, whereas A. givenchyi was restricted to the Salavan Province (southern Laos).Amphidromus syndromoideus sp.nov. is found at the type locality, Khammouan Province (central Laos), European Journal of Taxonomy 330: 1-40 (2017) only and A. xiengkhaungensis sp.nov. is rare and only found in an isolated limestone area at Nong Tang Village, Xieng Khaung Province, which is between the northern and central border at 800 m amsl.
The occurrence of A. roseolabiatus and A. xiengensis in the southern, central and northern parts of Laos may suggest (i) they originally had a widespread origin, (ii) one or both have been translocated by humans or (iii) they have been subjected to long range dispersal.These hypotheses await to be resolved.
The results show that the diversity of the species of Amphidromus in Laos is low compared to that in Thailand (Panha 1996;Sutcharit et al. 2015) and Vietnam (Schileyko 2011), where 19 and 23 species are known, respectively.However, this may simply reflect a collecting bias, having been spent less survey time and a smaller number of sites in Laos having been sampled compared to the other two countries, rather than demonstrating the actual species diversity.Thus, more extensive (intensity and coverage) sampling is required.

Fig. 8 .
Fig. 8. Genitalia, mating pairs, shell banding formula and radula morphology.A-B.Amphidromus (Syndromus) contrarius (Müller, 1774) from Timor (ZMA).A. Genital system.B. Internal structures of penis and vagina.C. Mating pair of Amphidromus (Syndromus) sp., showing the protruded vaginal simulator pilaster (vsp, red arrows) and its possible function as a stimulating organ.D. Schematic drawing of shell banding, where the numbers 1 to 6 on the last whorl indicate the position of each band.E-G.Radula morphology of Amphidromus (Syndromus) contrarius (Müller, 1774) from Timor (ZMA).E. Central tooth, with the first to fifth lateral teeth.F. Lateral teeth with the tricuspid marginal teeth transition.G. Outermost marginal teeth.Numbers indicate the order of the lateral and marginal teeth.Central tooth indicated by 'C'.
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locality and CUMZ nos No. of specimens Range, mean ± S.D. in mm of Number of whorls Shell height
fig. 13j-k.INKHAVILAY K. et al., Review and new species of Amphidromus in Laos Species,