Zoosyst. Evol. 97 (1) 2021, 1-20 | DOI 10.3897/zse.97.59143

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BERLIN

The operculate micro land snail genus Dicharax Kobelt & Moéllendorff,
1900 (Caenogastropoda, Alycaeidae) in Thailand, with

description of new species

Parin Jirapatrasilp!, Barna Pall-Gergely*, Chirasak Sutcharit', Piyoros Tongkerd!

1 Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

2 Plant Protection Institute, Centre for Agricultural Research, Herman Otto ut 15, H-1022 Budapest, Hungary

http://zoobank. org/1D5553 BA-2489-4F 2C-9527-B7E46B9B432B

Corresponding author: Piyoros Tongkerd (piyorose@hotmail.com)

Academic editor: Frank Kohler # Received 3 October 2020 # Accepted 12 November 2020 ¢@ Published 5 January 2021

Abstract

This study reviews the Dicharax species in Thailand. Altogether ten Dicharax species are reported, four of which are new to science
and described herein. They are Dicharax borealis Jirapatrasilp & Pall-Gergely sp. nov., Dicharax burchi Jirapatrasilp & Pall-Gergely
sp. nov., Dicharax panhai Jirapatrasilp & Pall-Gergely sp. nov. and Dicharax pongrati Jirapatrasilp & Tongkerd sp. nov. Alycaeus
davisi Godwin-Austen, 1914 is regarded as a junior subjective synonym of Alycaeus cucullatus Theobald, 1870 (= D. cucullatus)
based on a similar depressed-conical shell shape, a long sutural tube and a sharp swelling behind the peristome. Furthermore, the type
locality of Alycaeus pratatensis Panha & Burch, 1997 (= D. pratatensis) had to be amended. Most important characters to distinguish
Dicharax species are the general shell shape and relative lengths of teleoconch regions, whereas the spiral striation of R1, the shape of
swelling of R3, the outer peristome crenulation and protrusion, and the exterior opercular sculpture show large intraspecific variability.

Key Words

Cyclophoroidea, Gastropoda, Mollusca, taxonomy

Introduction

Alycaeidae Blanford, 1864 is a family of cyclophoroidean
operculate land snails. The alycaeid shell is characterized
by a sutural tube that corresponds with numerous perpen-
dicular microtunnels as described by Pall-Gergely et al.
(2016). This taxon has been treated as a subfamily of Cy-
clophoridae by several authors including Bouchet et al.
(2017), whereas it has been treated as a family of its own
by other sources (e.g. Egorov 2013). Based on the unique
gas exchange system of the shell and the presence of syn-
apomorphic genital anatomical characters, Pall-Gergely
et al. (2020b) proposed to treat this taxon at the family
level, which is followed here. This family ranges from
western India to Japan, including Indonesia in the south.
This group is known to be particularly diverse in three
regions, (1) the southeastern Himalaya, (2) Peninsular

Malaysia and Sumatra, and (3) northern Vietnam, north-
ern Laos and southern China (Pall-Gergely et al. 2017,
2020b, Aravind and Pall-Gergely 2018, Pall-Gergely
2019, Sajan et al. 2020). In Southeast Asia, alycaeid taxa
from Laos, Vietnam, and Peninsular Malaysia have re-
ceived attention in the past few years (Foon and Liew
2017, Pall-Gergely et al. 2017), whereas the taxa from
Thailand have remained poorly studied. Eleven alycaeid
species were described from Thailand before 2010, most-
ly classified as members of A/ycaeus Baird, 1850 (BEDO
2017; Table 1). However, reports of some species in the
checklist of Thai land snails (Solem 1966, Hemmen and
Hemmen 2001) are questionable as these were listed
without illustrations to confirm their correct identification
(i.e. Dicharax diplochilus (MOllendorff, 1887), Dicharax
fimbriatus (Bavay & Dautzenberg, 1912) and Dioryx
bacca (Pfeiffer, 1863)).

Copyright Parin Jirapatrasilp et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which
permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

Table 1. List of species in the family Alycaeidae reported from Thailand. Some species recorded in Solem (1966) and Hemmen and

Hemmen (2001) are exempted due to dubious identification.

Species [Original genus]
Alycaeus conformis
Fulton, 1902

Alycaeus gibbosulus
Stoliczka, 1872

Alycaeus somwangi
Dumrongrojwattana &
Maassen, 2008

Type locality
Perak State, Malaysia

Penang Island, Malaysia

Lub Lae Cave, Chonburi
Province, Eastern Thailand

Distribution records

Malaysia: Kelantan, Pahang, Selangor

and Johor
Thailand: Bangpae waterfall, Phuket
Peninsular Malaysia Thailand: Khao

References

Fulton (1902), Pall-Gergely et al.

(2016, 2020b), Foon and Liew
(2017)

Stoliczka (1872), Habe (1965),

Chong, Trang Foon and Liew (2017), Pall-Gergely
et al. (2020b)
Dumrongrojwattana and Maassen

(2008), Pall-Gergely et al. (2020b)

Only the type locality

Chamalycaeus canaliculatus
(Mollendorff, 1894) [Alycaeus]

Samui Islands, Gulf of Siam

Only the type locality Mollendorff (1894), Pall-Gergely

et al. (2017, 2020b)

Dicharax Ccaudapiscis
Pall-Gergely & Hunyadi, 2018

Wat Tham Pla, approx. 9 km
south-southwest from Mae Sai,
Chiang Rai Province, Northern

Thailand

Only the type locality Pall-Gergely and Hunyadi (2018),

Pall-Gergely et al. (2020b)

Dicharax cucullatus (Theobald,
1870) (syn. nov. Alycaeus
davisi Godwin-Austen, 1914)
[Alycaeus]|

Dicharax notus (Godwin-
Austen, 1914) [Alycaeus]
Dicharax omissus
(Godwin-Austen, 1914)
[Alycaeus]

Shan States

Fort Stedman, Burma

Siam and Shan boundary

Myanmar: Shan State
Thailand: Doi Chiang Dao, Doi Ang
Khang and Doi Inthanon, Chiang Mai

Theobald (1870), Godwin-Austen
(1914), Pall-Gergely et al.
(2020b), this study

Myanmar: Shan State
Thailand: Tham Luang Sa Koen, Nan
Myanmar: Shan State
Thailand: Tham Mae Lana, Mae Hong
Son

Godwin-Austen (1914), Pall-
Gergely et al. (2020b), this study
Godwin-Austen (1914). Pall-
Gergely et al. (2020b), this study

Dicharax pratatensis
(Panha & Burch, 1997)
[Alycaeus]

Dicharax stuparum
Pall-Gergely & Hunyadi, 2018

Doi Chiang Dao, Chiang Mai
Province, Northern Thailand
[non Pratat cave, Erawan
National Park, Kanchanaburi
Province]

50 m before Wat Phra That
Doi Tung, around the car park,
Doi Tung, Chiang Rai Province,
Northern Thailand

Only the type locality Panha and Burch (1997), this

study

Only the type locality Pall-Gergely and Hunyadi (2018),

Pall-Gergely et al. (2020b)

Dicharax borealis
Jirapatrasilp & Pall-Gergely
Sp. NOV.

Dicharax burchi
Jirapatrasilp & Pall-Gergely
Sp. NOV.

Dicharax panhai

Tham Ban Luang, Doi Ang
Khang, Chiang Mai Province,
Northern Thailand
Tham Phaya Nakharat, Khon
Kaen Province, Northeastern
Thailand

Pratat cave, Erawan National

Only the type locality This study

Myanmar: Hsihseng centre, Shan State
Thailand: Doi Chiang Dao, Chiang Mai
and Ban Soppong, Mae Hong Son
Only the type locality

This study

Pall-Gergely et al. (2020b), this

Jirapatrasilp & Pall-Gergely Park, Kanchanaburi Province, study
Sp. Nov. Western Thailand
Dicharax pongrati Jirapatrasilp Doi Chiang Dao, Chiang Mai Only the type locality This study

& Tongkerd sp. nov.

Province, Northern Thailand

Dioryx distortus (Haines, 1855)
[Cyclostoma]

Siam

Thailand Haines (1855), Kobelt (1902),

Pall-Gergely et al. (2020b)

Stomacosmethis christae
(Maassen, 2006) [Alycaeus]

at km 117.6 of road # 4 (Krabi
— Phang Nga), Krabi Province,
Southern Thailand

Only the type locality Maassen (2006), Pall-Gergely et

al. (2020b)

Stomacosmethis
matchacheepiorum
(Dumrongrojwattana &
Maassen, 2008) [Alycaeus]
Stomacosmethis perakensis
(Crosse, 1879) [Alycaeus]

Stomacosmethis roebeleni
(Mollendorff, 1894) [Alycaeus]

Stomacosmethis somnueki
(Panha & Patamakanthin,
2001) (syn. A. huberi Thach,
2018) [Alycaeus]

Khao Pratun Cave, Rayong
Province, Eastern Thailand

Buket Pondong, Perak
Samui Islands, Gulf of Siam

Ao Luk limestone areas, Krabi
Province, Southern Thailand

Only the type locality Dumrongrojwattana and Maassen

(2008), Pall-Gergely et al. (2020b)

Malaysia: Kedah and Perak
Thailand: Banang Pupo, Yala
Malaysia: Perlis
Thailand: Patthalung
Only the type locality

Crosse (1879), Foon and Liew
(2017), Pall-Gergely et al. (2020b)
Mollendorff (1894), Foon and Liew
(2017), Pall-Gergely et al. (2020b)
Panha and Patamakanthin (2001),

Thach (2018), Pall-Gergely et al.
(2020a, b)

Dicharax Kobelt & Mollendorff, 1900 (replacement
name for Charax Benson, 1859, non Charax Scopoli,
1777 [Pisces]) is one of the seven genera of the Alycaeidae
(Pall-Gergely et al. 2020b). It was originally described as
a subgenus of Al/ycaeus, and was diagnosed as follows:

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“constriction broad, contiguous to the aperture, and divided
more or less remotely from it, across the whorl, by a ridge
which is hollow internally” (Benson 1859). That diagno-
sis was adopted by later authors (Kobelt 1902, Gude 1921,
Egorov 2013). Pall-Gergely et al. (2017) elevated Dicharax

Zoosyst. Evol. 97 (1) 2021, 1-20

Figure 1. Geographical position of the type localities (white number in black circle) and other examined localities (black number
in white circle) of Dicharax spp. in this study. No. 1: D. cucullatus, 2: D. notus, 3: D. omissus, 4: D. pratatensis, 5: D. borealis sp.
nov., 6: D. burchi sp. nov., 7: D. panhai sp. nov., 8: D. pongrati sp. nov. The type localities of D. cucullatus and D. omissus (Shan
States and Siam and Shan boundary, respectively) are general and not plotted in the figure.

to a full genus and questioned the conspicuous hollow ridge
(termed swelling by Godwin-Austen 1914 and Pall-Gergely
et al. 2017) as feature diagnostic of the genus, and defined
Dicharax as having a low protoconch and lacking spiral stri-
ation on the entire shell. Dicharax caudapiscis Pall-Gergely
& Hunyadi, 2018 and D. stuparum Pall-Gergely & Hunya-
di, 2018 were described from Northern Thailand subse-
quently (Pall-Gergely and Hunyadi 2018). Following the
genus definition of Pall-Gergely et al. (2017), as many as
164 nominal species were assigned to Dicharax, including
three Alycaeus species that were formerly recorded from
Thailand or “Siam”, namely A. davisi Godwin-Austen,
1914, A. omissus Godwin-Austen, 1914, and A. pratatensis
Panha & Burch, 1997 (Pall-Gergely et al. 2020b).

In the present paper, based on the examination of the
CUMZ collections, the type locality of D. pratatensis has
to be amended. The specimens from Pratat Cave, Kan-
chanaburi, western Thailand (the former type locality
of A. pratatensis), are now described as a new species.
Three additional species are also new to science and de-
scribed from northern and northeastern Thailand. We also
provide diagnoses to three nominal species based on the
types and newly examined populations.

Material and methods

This study is based on material collected from throughout
Thailand since 1996 which is now deposited in the col-
lection of the Chulalongkorn University (CUMZ) (Fig. 1).
Additional specimens from HA and UF were examined by
BP-G. Live specimens were mostly collected from crevices

in limestone outcrops, while empty shells were collected
from the ground. Shells were measured using digital (scan-
ning electron microscope) SEM images. The counting of
the shell whorls (to the closest 1/8 whorl) follows Kerney
and Cameron (1979). The nomenclature of external aly-
caeid shell features follows Pall-Gergely et al. (2017). The
teleoconch is divided into three regions, namely; R1 (the
beginning of the teleoconch to the beginning of the differ-
ently ribbed region along the suture), R2 (the differently
ribbed area to the constriction) and R3 (the constriction to
the peristome) (see Pall-Gergely et al. 2017: fig. 1a, b). The
swelling on R3 is classified into either blunt (R3 gradually
swollen; Pall-Gergely et al. (2017: fig. 2q)) or sharp (R3
abruptly swollen and the swelling is narrower and more
elevated; Pall-Gergely et al. (2017: fig. 2r)). The peristome
is double, and its two parts are termed “inner peristome” or
“inner lip” and “outer peristome” or “outer lip” based on
Liew et al. (2014: fig. 10) and Pall-Gergely et al. (2017).

Institutional abbreviations

CUMZ, Chulalongkorn University Museum of Zoolo-
gy, Bangkok; FMNH, Field Museum of Natural History,
Chicago; HA, Collection of Andras Hunyadi, Budapest;
HNHM, Hungarian Natural History Museum, Budapest;
NHM, The Natural History Museum, London; NHMUK,
when citing specimen lots deposited in the NHM; SMF,
Forschungsinstitut und Naturmuseum Senckenberg,
Frankfurt am Main; UF, Florida Museum of Natural
History, University of Florida, Gainesville; UMMZ, Uni-
versity of Michigan Museum of Zoology, Ann Arbor.

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4

Other abbreviations

SH, shell height; SW, shell width.

Meaning of some Thai locality words

“Dor’, Mount; “Tham”, Cave; “Wat”, Temple.

Results

Taxonomy and systematics

Family Alycaeidae Blanford, 1864

Dicharax Kobelt & Millendorff, 1900

Alycaeus (Charax) Benson, 1859: 177; Pfeiffer 1865: 43, 44; Kobelt
and Mollendorff 1897: 149, 150 (invalid; preoccupied by Charax
Scopoli, 1777 [Pisces]).

Alycaeus (Dicharax) Kobelt & Mollendorff, 1900: 186 (replacement
name for Charax Benson, 1859, non Charax Scopoli, 1777 [Pi-
sces]); Kobelt 1902: 364; Gude 1921: 236.

Chamalycaeus (Dicharax) — Thiele 1929: 108; Wenz 1938: 478, fig.
1225; Egorov 2013: 37, fig. 66.

Chamalycaeus (Sigmacharax) Kuroda, 1943: 8; Egorov 2013: 37, 38.

Chamalycaeus (Cipangocharax) Kuroda, 1943: 11; Egorov 2013: 36.

Chamalycaeus (Awalycaeus) Kuroda, 1951: 73, 74; Egorov 2013: 35, 36.

Dicharax — Pall-Gergely and Asami 2017: 14; Pall-Gergely et al. 2017:
10, fig. 5; Pall-Gergely et al. 2020b: 48-53.

Type species. A/ycaeus hebes Benson, 1857, by subse-
quent designation (Gude 1921: 236).

Dicharax cucullatus (Theobald, 1870)
Figs 2, 3, 4A, B, 5A, 6H

Alycaeus cucullatus Theobald, 1870: 396, 397, pl. 18, fig. 2. Type local-
ity: Shan States [Myanmar]. Hanley and Theobald 1874: 39, pl. 96,
figs 1, 4; Reeve 1878: pl. 2, sp. 12; Godwin-Austen 1914: 407, pl.
155, fig. 5; Tarruella and Domenech 2011: 72.

Alycaeus (Charax) cucullatus — Kobelt and Mollendorff 1897: 150.

Alycaeus davisi Godwin-Austen, 1914: 408, pl. 148, fig. 9, 9a. Type
locality: Siam and Shan State boundary. New synonym.

Alycaeus (Dicharax) cucullatus — Kobelt 1902: 367, 368; Gude 1921:
244, 245.

Alycaeus (Chamalycaeus) davisi — Gude 1921: 226.

Dicharax cucullatus — Pall-Gergely et al. 2020b: 57, 58.

Dicharax davisi — Pall-Gergely et al. 2020b: 58.

Type material examined. Syntypes of Alycaeus
cucullatus NHMUK_ 1888.12.4.951-952 from Shan
States (2 shells; Fig. 2A). Syntypes of Alycaeus davisi
NHMUK 1903.7.1.1630 from Shan States (4 shells;
Fig. 2B).

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Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

Other material examined. CUMZ 7421 from Doi Chi-
ang Dao, Chiang Mai Province, Thailand, 19°14'26.7"N,
98°52'49.8"E, 24-28 May 1997, coll. S. Panha, J.B.
Burch, P. Dumrongrojwattana (1 shell; Figs 3A,
6H). CUMZ 5071 from Tham Ban Luang, Doi Ang
Khang, Chiang Mai Province, Thailand, 19°52'13.7"N,
99°02'44.1"E, 17 Mar. 2000, coll. S. Panha, P. Tongkerd
(34 shells; Figs 2C, D, 3B). CUMZ 7422 from Siribhum
Waterfall, Doi Inthanon, Chiang Mai Province, Thailand,
18°32'48.5"N, 98°30'44.0"E, 13-15 Oct. 2009, coll. C.
Sutcharit (71 shells; Figs 3C, 4A, B). CUMZ 7423 from
Wachirathan Waterfall, Doi Inthanon, Chiang Mai Prov-
ince, Thailand, 18°32'31.0"N, 98°35'53.8"E, 21 Jan.
2015, coll. P. Jirapatrasilp, R. Srisonchai, W. Sirtwut, T.
Seesamut, C. Sutcharit (10 shells; Fig. 3D). CUMZ 7424
from Doi Inthanon, 2,000 m a.s.1, Chiang Mai Province,
Thailand, 18°35'08.5"N, 98°29'03.4"E, 21 Jan. 2015, coll.
P. Jirapatrasilp, R. Srisonchai, W. Siriwut, T. Seesamut, C.
Sutcharit (3 shells; Fig. 3E). CUMZ 7432 from Doi Inth-
anon, ~1,700—2,000 m a.s.1, Chiang Mai Province, Thai-
land, 18°35'08.5"N, 98°29'03.4"E, 5—6 Oct. 2020, coll. P.
Jirapatrasilp, A. Pholyotha, W. Sirtwut, N. Likhitrakarn,
C. Sutcharit (6 specimens in ethanol; Fig. 5A).

Diagnosis. Shell medium-sized (SH up to 3.5 mm, SW
up to 5.5 mm), depressed-conical. Spire ca. 1/5 of shell
height. R1 with regular, strong ribs; R2 longer than R3;
R2 with 49-57 ribs. R3 with sharp swelling near aper-
ture. Aperture round. Inner peristome with four to five
indentations, always with parieto-columellar indentation,
sometimes weak at basal. Outer peristome fringed, slight-
ly reflected but not conspicuous. Umbilicus round. Oper-
culum multispiral with elevated lamella.

Distribution. Shan State, Myanmar (Gude 1921), and
Chiang Mai Province, Thailand.

Remarks. This species was originally described from
Shan State and diagnosed by its fringed peristome with
five indentations (Theobald 1870). Later, Godwin-Austen
(1914) described Alycaeus davisi with a less fringed peri-
stome with four indentations from Siam and Shan State
boundary. Upon examining the type specimens, both
species agree 1n having a depressed-conical shell shape,
a long R2 and a sharp swelling of R3 near the aperture
(Fig. 2A, B). The types of A. cucullatus differ from those
of A. davisi in having a more fringed peristome and
more indentations. However, based on recently collected
specimens, we conclude that this variation is to be inter-
preted as intraspecific as we found that this crenulation
may vary even within the same population from nearly
smooth (Fig. 4A) via slight (Fig. 4B) to strong (Fig. 2C,
D). Because both species were described from the same
geographical region, Alycaeus davisi is herein regarded
as a junior subjective synonym of Alycaeus cucullatus.
Refer to Discussion regarding the color of living speci-
men and variation in spiral striation.

Dicharax cucullatus differs from other species with sim-
ilar shell shape and fringed peristome, 1.e. D. anthostoma
(Mollendorff, 1885) (Pall-Gergely et al. 2017: fig. 19a,
b) from China, D. ataranensis (Godwin-Austen, 1914)

Zoosyst. Evol. 97 (1) 2021, 1-20

Figure 2. Dicharax cucullatus A. Syntype of Alycaeus cucullatus, NHMUK 1888.12.4.951; B. Syntype of A/ycaeus davisi, NHMUK
1903.7.1.1630; C, D. Specimens CUMZ 5071 from Tham Ban Luang, Doi Ang Khang, Chiang Mai Province. Close-up images of
the aperture not to scale. Photo: NHM (A, B..).

(Pall-Gergely et al. 2020b: figs 11, 12) from Myanmar
and D. fimbriatus (Pall-Gergely et al. 2017: figs 35-37)
from China and Vietnam in possessing a sharp swelling
nearer to the aperture. In addition, D. cucullatus differs
from D. anthostoma in having shorter distance between
the inner and outer peristomes and from D. ataranensis in
possessing a shorter R3. Although D. tangmaiensis (Chen

& Zhang, 2001) (Pall-Gergely et al. 2020b: fig. 14) from
Tongmai Town, Bomi County, Tibet Autonomous Region,
China is very similar to D. cucullatus, the distance between
both species’ type localities is approximately 1,100 km.
Thus, the status of D. tangmaiensis needs further scrutiny.

Some specimens from Doi Inthanon possess a more de-
pressed shell with a lower spire, a very low swelling of R3

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6 Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

Figure 3. Dicharax cucullatus from Chiang Mai Province A. Specimen CUMZ 7421 from Doi Chiang Dao; B. Specimen CUMZ
5071 from Tham Ban Luang, Doi Ang Khang; C. Specimen CUMZ 7422 from Siribhum Waterfall, Doi Inthanon; D. Specimen
CUMZ 7423 from Wachirathan Waterfall, Doi Inthanon; E. Specimen CUMZ 7424 from Doi Inthanon, 2000 m a.s.1. Close-up
images of the aperture not to scale.

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Zoosyst. Evol. 97 (1) 2021, 1-20

and a nearly smooth inner peristome (Fig. 4A) very simi-
lar to D. borealis sp. nov. However, D. cucullatus could be
distinguished from D. borealis sp. nov. by a round aper-
ture and always having a parieto-columellar indentation.

Dicharax notus (Godwin-Austen, 1914)
Figs 4C, D, 5B, 6E, 7A, B

Alycaeus notus Godwin-Austen, 1914: 411, pl. 155, fig. 12. Type lo-
cality: Fort Stedman, Burma [Maing Thauk or Mine Thauk located
in the east side of Inle Lake south of Nyaungshwe, Nyaungshwe
Township, Taunggyi District, Shan State, Myanmar].

Alycaeus (Dicharax) notus — Gude 1921: 262.

Dicharax notus — Pall-Gergely et al. 2020b: 69.

Type material examined. Syntypes NHMUK
1903.7.1.3065 from Fort Stedman (15 shells; Fig. 4C).

Other material examined. CUMZ 7425 from Tham
Luang Sa Koen, Nan Province, Thailand, 19°22'00.1"N,
100°32'28.4"E, 19 Jan. 2017, coll. C. Sutcharit, A. Pholy-
otha (174 shells and 13 specimens in ethanol; Figs 4D,
5B, 6E, 7A, B).

Diagnosis. Shell small (SH up to 2.2 mm, SW up to
3.6 mm), depressed-conical. Spire ca. 1/5 of shell height.
R1 with regular ribs; R2 as long as or shorter than R3;
R2 with 48-50 ribs. R3 with low blunt central swelling,
more elevated in newly examined population. Aperture
round. Inner peristome without indentation, with parie-
to-columellar angle in newly examined population. Outer
peristome expanded, reflected. Umbilicus round. Opercu-
lum multispiral either with or without elevated lamella.

Distribution. Shan State, Myanmar (Gude 1921), and
Nan Province, Thailand.

Remarks. Similar to D. cristatus (Mollendorff, 1886)
from China and Vietnam as well as D. depressus (Bavay
& Dautzenberg, 1912) and the rounded peristome morph
of D. fimbriatus (the latter two known from Pac Kha,
northern Vietnam) in shell size and shape, length of R2
and R3, and position of the swelling in R3 (Pall-Gergely
et al. 2017). The specimens from Nan Province, Thai-
land (Fig. 4D) differ from the type specimens in having
a longer R3, a more shouldered R3 swelling, a stronger
descending aperture, and a parieto-columellar angle. De-
spite those differences, we preliminarily identified the
specimens from Nan Province as D. notus. Refer to Dis-
cussion regarding the color of living specimen and varia-
tion in operculum morphology.

Dicharax omissus (Godwin-Austen, 1914)
Figs 6A, 8A, B

Alycaeus omissus Godwin-Austen, 1914: 411, pl. 155, fig. 13. Type lo-
cality: Siam and Shan State boundary.

Alycaeus (Chamalycaeus) omissus — Gude 1921: 231.

Dicharax (?) omissus — Pall-Gergely et al. 2020b: 100.

Type material examined. Syntypes NHMUK
1903.7.1.1228 from Siam & Shan boundary (2 shells;
Fig. 8A).

Other material examined. CUMZ 7426 from
Tham Mae La Na, Mae Hong Son Province, Thailand,
19°34'28.9"N, 98°12'57.4"E, 19 Jan. 2017, coll. C.
Sutcharit (1 shell; Figs 6A, 8B).

Diagnosis. Shell very small (SH up to 1.7 mm, SW
up to 2.7 mm), depressed-conical. Spire ca. 1/4 of shell
height. R1 with regular, strong ribs; R2 shorter than R3;
R2 with 35—36 ribs. R3 with blunt central swelling. Ap-
erture round. Inner peristome without indentation, with
beak-like basal protrusion in newly examined population.
Outer peristome expanded, not reflected. Umbilicus round.

Distribution. Border region between Thailand and
Myanmar (Gude 1921), and Mae Hong Son Province,
Thailand.

Remarks. The specimen from Mae Hong Son Prov-
ince (Fig. 8B) exhibits stronger R1 ribs and possesses a
beak-like protrusion at the base of the aperture, which is
absent in the syntype (Fig. 8A). Apart from these differ-
ences, this specimen is nearly identical to the syntype in
terms of shell size and shape, and R2 and R3 length. In
addition, the locality of this specimen lies only approx-
imately 12 km from the boundary between Thailand and
Shan State, Myanmar. We thus identify this specimen as
D. omissus. The most similar species to D. omissus is
D. notus, which is larger and has reflected outer peristome.

Dicharax pratatensis (Panha & Burch, 1997)
Figs 6B, 8C, D

Alycaeus pratatensis Panha & Burch, 1997: 119-122, fig. 2a—c. Type
locality: “Tham Pratat, Erawan National Park, Kanchanaburi Prov-
ince, Thailand”, hereby emended to: “Doi Chiang Dao, Chiang Mai
Province, Northern Thailand”.

Type material examined. Holotype CUMZ Cy 001
(Fig. 8C), paratypes CUMZ Cy 002 (2 shells; Fig. 8D),
FMNH (1 shell), NHMUK 20200324 (2 shells) and
UMMZ (1 shell) from Doi Chiang Dao, Chiang Mai Prov-
ince, Thailand, 19°14'26.7"N, 98°52'49.8"E, 24-28 May
1997, coll. S. Panha, J.B. Burch, P.- Dumrongrojwattana.

Other material examined. CUMZ 7427 from Doi Chi-
ang Dao, Chiang Mai Province, Thailand, 19°14'26.7"N,
98°52'49.8"E, 24-28 May 1997, coll. S. Panha, J.B.
Burch, P. Dumrongrojwattana (16 shells; Fig. 6B).

Diagnosis. Shell small (SH up to 2 mm, SW up to
3.2 mm), depressed-conical. Spire ca. 1/6 of shell height.
R1 with regular, very strong ribs; R2 shorter than R3; R2
with 44—51 ribs. R3 with prominent, blunt swelling near
aperture, anterior slope of swelling steeper than posterior
slope. Aperture round. Inner peristome thickened, pro-
truding, with slight parieto-columellar angle. Outer peri-
stome expanded, not reflected. Umbilicus round. Opercu-
lum multispiral.

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Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

Figure 4. A, B. Dicharax cucullatus, specimens CUMZ 7422 from Siribhum Waterfall, Doi Inthanon, Chiang Mai Province; A. With
operculum; C, D. Dicharax notus C. Syntype NHMUK 1903.7.1.3065; D. Specimen CUMZ 7425 from Tham Luang Sa Koen, Nan
Province. Close-up images of the aperture not to scale. Photo: NHM (C.).

Distribution. Known only from Doi Chiang Dao,
Chiang Mai Province, Thailand.

Remarks. Re-examination of the type materials (holotype
Cy O01: Fig. 8C and paratypes Cy 002: Fig. 8D) deposited
in CUMZ and figured in the original description (Panha and
Burch 1997: fig. 2) revealed that the locality code associated

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with the types points to “Doi Chiang Dao”. However, the
locality of the paratypes of Alycaeus pratatensis deposited
in SMF (inv. number: 331452) appears as “Tham Pratat,
Erawan National Park, Kanchanaburi Province”. After we
compared all the type materials to the same specimen lots
of both localities housed in the general CUMZ collections

Zoosyst. Evol. 97 (1) 2021, 1-20

A

Figure 5. Living Dicharax specimens. A. Dicharax cucullatus,
specimen CUMZ 7432 from Doi Inthanon, Chiang Mai Provy-
ince; B. Dicharax notus, specimen CUMZ 7425 from Tham
Luang Sa Koen, Nan Province. Both photographed in the labo-
ratory. Not to scale. Photo: A. Pholyotha.

and communicated with S. Panha, it became evident that the
type material might have been mis-allocated. We conclude
that the published type locality of A. pratatensis (Tham Pra-
tat, Erawan National Park, Kanchanaburi Province, Thai-
land) is incorrect, and another species (Dicharax panhai sp.
nov.) lives there. Thus, the type locality of A. pratatensis
is hereby amended to Doi Chiang Dao, Chiang Mai Prov-
ince, Thailand. Pall-Gergely et al. (2020b: 71) transferred
A. pratatensis to Dicharax based on the examination of
paratype specimens deposited in the Senckenberg Museum
(SMF 331452). However, the present study revealed that
those shells and all other CUMZ specimens from Tham Pra-
tat, Erawan National Park, Kanchanaburi Province, Thai-
land belong to D. panhai sp. nov. (see below).

Dicharax borealis Jirapatrasilp & Pall-Gergely, sp. nov.
http://zoobank.org/80FC8FC0-D804-4BE6-B5F5-5CD400772BBF
Figs 6G, 9

Type material. Holotype CUMZ 5072/1 (Fig. 9),
paratypes CUMZ 5072/2 (2 shells; Fig. 6G), NHMUK

9

20200325 (1 shell) and SMF (1 shell) from Tham Ban
Luang, Doi Ang Khang, Chiang Mai Province, Thai-
land, 19°52'13.7"N, 99°02'44.1"E, 17 Mar. 2000, coll. S.
Panha, P. Tongkerd.

Diagnosis. Shell medium-sized (SH up to 2.7 mm, SW
up to 4.4 mm), depressed-conical. Spire ca. 1/6 of shell
height. R1 with regular ribs; R2 twice longer than R3; R2
with ca. 72 ribs. R3 with very low, elongated swelling.
Aperture oval. Inner peristome thickened, with three very
shallow indentations, always without parieto-columellar
indentation. Outer peristome expanded, not reflected.
Umbilicus round.

Description. Shell medium-sized (SH up to 2.7 mm,
SW up to 4.4 mm), depressed-conical, solid, translucent,
pale yellowish. Shell outline oval in apical view, spire ca.
1/6 of shell height. Whorls ca. 4’. Protoconch low, ca. two
whorls, glossy and smooth. R1 ca. 1% whorls, with fine,
regular ribs; with ca. 21 ribs in 4 whorl adjoining R2, ribs
sharper near suture and inside umbilicus than in middle of
body whorl. Boundary between R1 and R2 distinct as R2
contains more close-set and thicker ribs than R1; R2 with
ca. 72 ribs that are curved towards aperture; R2 ca. 1/3
whorl and twice longer than R3. Boundary between R2
and R3 distinct due to shallow constriction; R3 with fine
growth lines; with very low and elongated swelling. Ap-
erture oval; slightly oblique to shell axis. Peristome dou-
ble with regular outer peristome. Inner peristome thick,
expanded, with three very shallow indentations, always
without parieto-columellar indentation. Outer peristome
thinner, expanded, not reflected, multi-layered (visible
mostly in lateral view). Umbilicus round, open, approx-
imately one third of shell width. Operculum unknown.

Etymology. The specific epithet “borealis” refers
to the occurrence of the new species from the northern
mountain of Thailand.

Distribution. Known only from the type locality in
Chiang Mai Province, Thailand.

Remarks. Differs from the sympatric D. cucullatus
in having a wider shell, a rather oval outline, a shorter
R3 with very low and elongated swelling, a less fringed
and oval aperture and an inner peristome with three very
shallow indentations, always without any parieto-colu-
mellar indentation.

Dicharax burchi Jirapatrasilp & Pall-Gergely, sp.
nov.
http://zoobank.org/8797FE78-84C5-4887-A F6 1 -923C1E341734
Figs 6F, 10, 11A

Type material. Holotype CUMZ 7428/1 (Fig. 10A), para-
types CUMZ 7428/2 (1 shell and 6 specimens in ethanol;
Fig. 6F), HNHM (1 shell), NHMUK 20200326 (2 shells)
and SME (2 shells) from Tham Phaya Nakharat, Khon
Kaen Province, Thailand, 16°48'32.8"N, 101°57'23.9"E,
21 July 2020, coll. P. Tongkerd, A. Pholyotha.

Other material examined. UF 347279 from limestone
pass 10.0 km NW Ban Soppong, Mae Hong Son Prov-
ince, Thailand, 19°33.183'N, 98°11.533'E, 800 m as.l.,

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10

D D. pongrati sp. n.

G D. borealis sp. n.

Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

E D. notus

H D. cucullatus

Figure 6. Synoptic view of the eight Dicharax taxa in Thailand. A. Dicharax omissus, specimen CUMZ 7426 (gold plated);
B. Dicharax pratatensis, specimen CUMZ 7427; C. Dicharax panhai sp. nov., paratype CUMZ 7429/2; D. Dicharax pongrati sp.
nov., paratype CUMZ 7430/2; E. Dicharax notus, specimen CUMZ 7425; FE. Dicharax burchi sp. nov., paratype CUMZ 7428/2;

G. Dicharax borealis sp. nov., paratype CUMZ 5072/2; H. Dicharax cucullatus, specimen CUMZ 7421.

23 Jun. 1987, coll. F.G. Thompson (1 shell; Fig. 10D).
UF 345622 from 10.2 km WNW of Soppong, Road 1095,
Mae Hong Son Province, Thailand, 19°33'N, 98°03'E,
820 maz.s.1., 20 Mar. 1988, coll. K. Auffenberg (3 shells).
HA (locality code: 2018/41) from Hsihseng centre E ca.
6 km, right side of rd. + 500 m on unpaved rd., limestone
hill, Shan State, Myanmar, 20°8.002'N, 97°18.024'E,
1000 m a.s.l., 7 Oct. 2018, coll. A. Hunyadi, K. Okubo,
J.U. Otani (1 shell; Fig. 11A). CUMZ 7431 from Doi Chi-
ang Dao, Chiang Mai Province, Thailand, 19°14'26.7"N,
98°52'49.8"E, 24-28 May 1997, coll. S. Panha, J.B.
Burch, P. Dumrongrojwattana (4 shells; Fig. 10B, C).
Diagnosis. Shell small (SH up to 3.6 mm, SW up to
3.5 mm), conical. Spire ca. % of shell height. RI with
regular, strong ribs; R2 as long as R3; R2 with 36—43
ribs. R3 with either sharp and narrow or blunt and more

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elongated swelling in the middle of R3 or near aperture.
Aperture round. Inner peristome blunt, slightly protrud-
ing. Outer peristome expanded (most conspicuously at
the upper palatal position and near the umbilicus), re-
flected. Umbilicus partly or entirely covered by expanded
outer peristome. Operculum multispiral.

Description. Shell small (SH up to 3.6 mm, SW up
to 3.5 mm), conical, solid, semitransparent, yellowish to
pale orange. Shell outline round in apical view, spire ca.
/2 Of shell height. Whorls approaching 5, last whorl large.
Protoconch low, ca. two whorls, glossy and smooth. R1
ca. 2 whorls, with regular, strong ribs; with ca. 21 ribs in
Ys whorl adjoining R2, ribs sharper near suture and flatter
near umbilicus, most prominent when approaching R2.
Boundary between R1 and R2 distinct as R2 contains
more close-set ribs than R1; R2 with 36—43 ribs that are

Zoosyst. Evol. 97 (1) 2021, 1-20

Tal

Figure 7. Close-up images of the aperture showing the operculum in situ. A, B. Dicharax notus, specimens CUMZ 7425; A. Without
lamella; B. With elevated lamella; C. Dicharax pongrati sp. nov., paratype CUMZ 7430/2, without lamella, probably lost due to corrosion.

curved towards aperture; R2 ca. '%4 whorl, as long as R3.
Boundary between R2 and R3 distinct due to shallow
constriction; R3 smooth with indistinct growth lines;
with either sharp and narrow or blunt and more elongated
swelling in the middle of R3 or near aperture. Aperture
round; slightly oblique to shell axis. Peristome double
with prominent outer peristome. Inner peristome blunt,
slightly protruding. Outer peristome strongly thickened,
expanded, reflected, most conspicuously at the upper
palatal position and near the umbilicus, multilayered
(visible in lateral view). Umbilicus is partly or entirely
closed by the reflected outer peristome. Operculum thin;
multispiral ridges not significantly elevated.

Etymology. In honor of Prof. John B. Burch, a prom-
inent American malacologist, who, together with Prof. S.
Panha, extensively studied the taxonomy and systematics
of micro land snails of Thailand.

Distribution. The new species is known from the type
locality, Tham Phaya Nakharat, Khon Kaen Province,
Northeastern Thailand. The other localities are Doi Chi-
ang Dao, Chiang Mai Province and Ban Soppong, Mae
Hong Son Province, Northern Thailand, and also from
Shan State, Myanmar.

Remarks. Differs from D. vestitus (Blanford, 1862)
from Moditoung [Modi Taung, Arakan Hills] (Fig. 11B),
and its subspecies D. v. akyabensis (Godwin-Austen,
1914) from Baumi, Akyab [Sittwe] (Fig. 11C), both from
Rhakhine State, Myanmar, by having a smaller shell with
a higher spire, a longer last whorl and a less distinct and
a narrower constriction between R2 and R3. Differs from
D. conicus (Godwin-Austen, 1871) from Samiamri, E of
the Kopili R., Assam State, India (Fig. 11D) in having
a longer last whorl, more close-set ribs on R2, and the
inner and outer peristomes are narrower and less reflect-
ed. Differs from D. imitator Pall-Gergely & Hunyadi in
Pall-Gergely et al., 2017 from Guangxi, China in having a
less smooth R1, a much thicker peristome, a longer R2, a
shallower constriction between R2 and R3, the last whorl
less oblique compared to the columellar axis and a less
triangular aperture (Pall-Gergely et al. 2017).

This species exhibits the variation of R1 sculpture from
nearly smooth (Fig. 10A) to distinctly ribbed (Fig. 10C, D)
and R3 swelling from sharp (Fig. 10B, C) to blunter and

longer by having the anterior slope of swelling steeper than
posterior slope (Fig. 10D). In addition, the umbilicus 1s
open, or covered by the reflected outer peristome. The latter
trait even shows variation within the same population (may-
be also depends on the age of the examined specimens).

Dicharax panhai Jirapatrasilp & Pall-Gergely, sp. nov.
http://zoobank.org/C6236997-4DFE-43BD-97 1 B-29C5E071A89E
Figs 6C, 12A-C

Dicharax pratatensis — Pall-Gergely et al. 2020b: 71, 72.

Type material. Holotype CUMZ 7429/1 (Fig. 12A),
paratypes CUMZ 7429/2 (16 shells; Figs 6C, 12B),
HNHM (2 shells), NHMUK 20200327 (2 shells), para-
types of “Alycaeus pratatensis Cy 003” FMNH (2 shells),
SMF 331452 (2 shells; Fig. 12C) and UMMZ (2 shells)
from Tham Pratat, Erawan National Park, Kanchanabu-
ri Province, Thailand, 14°23'50.8"N, 99°04'56.3"E, 230
a.s.l., 26 Oct. 1996, coll. S. Panha.

Diagnosis. Shell small (SH up to 2.4 mm, SW up to
3.1 mm), depressed-conical with triangular dorsal side and
widened, sigmoid last whorl. Spire ca. 1/3 of shell height.
R1 with regular, thread-like ribs; R2 twice shorter than
R3; R2 with ca. 18 ribs. R3 with blunt central swelling.
Aperture round. Inner peristome thick, protruding. Outer
peristome expanded, not reflected. Umbilicus elliptical.

Description. Shell small (SH up to 2.4 mm, SW up
to 3.1 mm), depressed-conical with triangular dorsal
side and widened, sigmoid last whorl; solid, worn out
white; the exact color of non-weathered (fresh) shells
unknown. Shell outline oval in apical view, spire ca.
1/3 of shell height. Whorls ca. 4 and 1/8. Protoconch
low, ca. two whorls, glossy and smooth. R1 ca. 1%
whorls with fine, regular, thread-like ribs; with ca. 14
ribs in '4 whorl adjoining R2, ribs sharper near suture
and flatter near umbilicus. Boundary between R1 and
R2 distinct as R2 contains more close-set ribs than R1;
R2 with ca. 18 ribs that are curved towards aperture;
R2 ca. 1/8 whorl, twice shorter than R3. Boundary be-
tween R2 and R3 distinct due to shallow constriction;
R3 initially coils horizontally forming a flat base, but

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2 Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

Figure 8. A, B. Dicharax omissus A. Syntype NHMUK 1903.7.1.1228; B. Specimen CUMZ 7426 from Tham Mae La Na, Mae
Hong Son Province C, D. Dicharax pratatensis C. Holotype CUMZ Cy 001; D. Paratype CUMZ Cy 002 from Doi Chiang Dao,
Chiang Mai Province. Close-up images of the aperture not to scale.

aperture strongly descent being strongly oblique to stome. Inner peristome thick, protruding. Outer peri-
Shell axis; R3 mostly smooth with indistinct growth stome slightly expanded, not reflected, multi-layered
lines that become stronger near aperture; with blunt (visible mostly in lateral view). Umbilicus elliptical,
central swelling. Aperture round; slightly oblique to open, slightly more than one third of shell width. Oper-
Shell axis. Peristome double with regular outer peri- culum unknown.

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Zoosyst. Evol. 97 (1) 2021, 1-20

Figure 9. Dicharax borealis sp. nov., holotype CUMZ 5072/1.

Etymology. In honor of Prof. Somsak Panha, a prom-
inent Thai malacologist and our beloved professor who
initiated the taxonomic and systematic study of land
snails and other terrestrial invertebrates in Thailand and
surrounding areas of mainland Southeast Asia.

Distribution. The new species is known only from the
type locality in Kanchanaburi Province, Thailand.

Remarks. Similar to D. pratatensis from Doi Chi-
ang Dao, Chiang Mai Province, Thailand in having
a depressed-conical shell shape and R3 with blunt
swelling, but differs in having a conical apical part on
a wide shell base, less distinct ribs of R1 and shorter
R2 with less ribs. The short R2 and breathing tube is
also exhibited in D. abdoui Pall-Gergely in Pall-Gerge-
ly et al., 2017 from Khammouane Province, Laos and
D. stuparum from Chiang Rai Province, Northern
Thailand, but D. panhai sp. nov. is larger, comprises
more whorls, has a more elevated spire and a larger
last whorl (Pall-Gergely et al. 2017, Pall-Gergely and
Hunyadi 2018).

Dicharax pongrati Jirapatrasilp & Tongkerd, sp. nov.
http://zoobank.org/92117A2E-1578-41D6-845C-8223B815B272
Figs 6D, 7C, 12D

Type material. Holotype CUMZ 7430/1 (Fig. 12D),
paratypes CUMZ 7430/2 (56 shells; Figs 6D, 7C),
HNHM (2 shells), NHMUK 20200328 (2 shells) and
SMF (2 shells) from Doi Chiang Dao, Chiang Mai
Province, Thailand, 19°14'26.7"N, 98°52'49.8"E,
24-28 May 1997, coll. S. Panha, J.B. Burch, P.
Dumrongrojwattana.

rs

Diagnosis. Shell medium-sized (SH up to 2.3 mm, SW
up to 4.4 mm), lenticular, depressed-conical. Spire ca. 4
of shell height. R1 with regular, thread-like ribs; R2 three
times longer than R3; R2 with ca. 76 ribs. R3 strongly re-
duced, without swelling. Aperture round. Inner peristome
with two shallow indentations. Outer peristome expand-
ed, slightly reflected. Umbilicus elliptical. Operculum
multispiral, with or without elevated lamella.

Description. Shell medium-sized (SH up to 2.3 mm,
SW up to 4.4 mm), lenticular, depressed-conical, solid,
translucent, yellowish to pale orange. Shell outline oval
in apical view, spire ca. 4 of shell height. Whorls ca.
4 and 1/8. Protoconch low, ca. two whorls, glossy and
smooth. R1 ca. 1% whorls with fine, regular, thread-like
ribs; with ca. 17 ribs in '4 whorl adjoining R2, ribs more
elevated and sharper near suture and flatter near umbi-
licus and at the edge of body whorl. Boundary between
R1 and R2 distinct as R2 contains denser and thicker
ribs than R1; R2 with ca. 76 ribs that are curved towards
aperture; R2 ca. 1/3 whorl, three times longer than R3.
Boundary between R2 and R3 distinct due to shallow
constriction; R3 strongly reduced, without swelling,
practically the constriction continues directly to outer
peristome. Aperture round; slightly oblique to shell axis.
Peristome double with regular outer peristome. Inner
peristome slim, slightly protruding, with two shallow in-
dentations. Outer peristome thickened, expanded, slight-
ly reflected, multilayered (visible in lateral view). Um-
bilicus elliptical, open, approximately one third of shell
width. Operculum either thin with low lamella or thick
with elevated lamella.

Etymology. In honor of Pongrat Dumrongrojwattana,
a Thai malacologist who has studied micro land snails of
Thailand and was one of the collectors of this new species.

Distribution. The new species is known only from the
type locality in Chiang Mai Province, Thailand.

Remarks. Differs from the sympatric and similar
depressed-conical D. pratatensis in having a wider and
more depressed shell, a much longer R2, a shorter R3
without a swelling and two shallow indentations at the
inner peristome.

Discussion

Dicharax species inhabiting China, Laos and Vietnam
have been revised recently by Pall-Gergely et al. (2017).
Several other species have been included in Dicharax
in a recent family-wise revision without examining spe-
cies-level taxonomy (Pall-Gergely et al. 2020b). Here we
report a total of ten Dicharax species from Thailand, six
out of ten species being recorded from their type localities
only, and the remaining species with additional occur-
rences within the vicinity of the type locality which rang-
es wider within Thailand or both Thailand and Myanmar.
Nearly all Dicharax species are known from the north-
ern mountainous region except for D. panhai sp. nov.,
the type locality of which is in the Tenasserim Range.

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14 Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

Figure 10. Dicharax burchi sp. nov. A. Holotype CUMZ 7428/1 with operculum; B, C. Specimen CUMZ 7431 from Doi Chiang
Dao, Chiang Mai Province; D. Specimen UF 345622 from 10.2 km WNW of Soppong, Road 1095, Mae Hong Son Province. Close-
up images of the aperture not to scale.

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Zoosyst. Evol. 97 (1) 2021, 1-20 15

Figure 11. A. Dicharax burchi sp. nov., specimen HA (locality code: 2018/41) from Hsihseng centre E ca. 6 km, limestone hill,
Shan State, Myanmar; B. Dicharax vestitus, holotype NHMUK 1906.4.4.53; C. Dicharax vestitus akyabensis, syntype NHMUK
1888.12.4.251—252; D. Dicharax conicus, syntype NHMUK 1903.7.1.2674. Photo: NHM (B-D).

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16 Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

oe

ee
: wth amit,

Figure 12. A—C. Dicharax panhai sp. nov. A. Holotype CUMZ 7429/1; B. Paratype CUMZ 7429/2; C. paratype SMF 331452 (para-
type of “Alycaeus pratatensis Cy 003” from Tham Pratat, Erawan National Park, Kanchanaburi Province, Thailand). D. Dicharax
pongrati sp. nov., holotype CUMZ 7430/1 Close-up images of the aperture not to scale. Photo: B. Pall-Gergely, courtesy Ronald
Janssen (C.).

In addition, the populations here assigned to D. burchi in terms of shell characters. Nevertheless, we currently
sp. nov. inhabit a wide area from Myanmar to northeast- _— refrain from describing local populations as subspecies.
ern Thailand (Fig. 1) and shows considerable variation The disjunct distribution of Dicharax species has been

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Zoosyst. Evol. 97 (1) 2021, 1-20 17
Table 2. Comparison of diagnostic conchological characters among Dicharax species in this study.
Species Shell Spire | R2 length | No. Swelling of R3_ | Aperture| Outer peristome Inner peristome Umbilicus
shape to compared | of R2 shape
shell to R3 ribs
height
ratio
D. cucullatus |depressed-| ~1/5 49-57 sharp; near fringed, slightly with four to five round
conical aperture reflected but not indentations, always
conspicuous with parieto-columellar;
sometimes weak at
basal
D. notus depressed-) ~1/5 low blunt; central; expanded, reflected | without indentation; round
conical more elevated in with parieto-columellar
newly examined angle in newly
population examined population
D. omissus depressed-| ~1/4 blunt; central expanded, not without indentation; round
conical reflected with beak-like basal
protrusion in newly
examined population
D. pratatensis |depressed-| ~1/6 prominent, blunt; expanded, not without indentation; round
conical near aperture; reflected with slight parieto-
anterior slope columellar angle
steeper than
posterior slope
D. borealis depressed-| ~1/6 very low and expanded, not with three very shallow | round
Sp. nov. conical elongated reflected indentations, always
without parieto-
columellar
D. burchi sp. conical ~1/2 sharp and narrow expanded, reflected,} without indentation partly or
nov. or blunt and more most conspicuously entirely
elongated; central at the upper palatal covered
or near aperture position and near by
the umbilicus expanded
outer
peristome
D. panhai sp. |depressed-| ~1/3 twice blunt; central expanded, not without indentation elliptical
nov. conical shorter reflected
with than R3
triangular
dorsal
side
D. pongrati lenticular, | ~1/4 three not swelling expanded, slightly with two shallow elliptical
Sp. nov. depressed- times reflected indentations
conical longer
than R3

reported in D. diminutus (Heude, 1885) from China,
whereas some species, e.g. D. fimbriatus and D. cristatus,
show a wide distribution range from China to Vietnam
and Laos (Pall-Gergely et al. 2017). Additional, especial-
ly molecular phylogenetic analyses could reveal that the
morphologically distinct populations currently treated as
a single species might represent distinct species.

The alycaeid shell is complicated mostly due to the
three clearly distinguishable regions of the teleoconch
(R1, R2, R3) having their own characteristics of sculp-
ture (the most important is the rib density), length and
morphology. Previous revisions (Pall-Gergely et al. 2017,
2020b, Pall-Gergely and Auffenberg 2019) showed that
most populations are recognizable, i.e. possess unique
combinations of characters that distinguish them from
other conspecific populations. Due to the high variability
among populations, the most useful approach is being a
lumper, in order not to over split the alycaeid genera and
not to describe many unrealistic species (Pall-Gergely et
al. 2020b: 27). Thus, instead of describing every recog-
nizable population as distinct species (or even subspe-
cies), we only distinguish species with unique character

states, and attempt to apply existing nominal species to
newly examined populations as much as possible. The
latter is the situation for D. notus and D. omissus, which
have so far been known from single populations. The
populations we examined and identified as D. notus and
D. omissus, differ from their respective type specimens in
some characters, which we interpret as being insufficient
for distinguishing them at species level. Moreover, both
Species are variable and widespread, as revealed by the
examination of additional populations from Thailand and
Myanmar (Pall-Gergely et al. in prep.).

The recent alycaeid revisions (Pall-Gergely et al.
2017, Pall-Gergely and Auffenberg 2019) also showed
that most important characters to distinguish species are
the relative lengths of regions (especially R2 and R3) and
the general shell shape, whereas other characters, such
as the shape of swelling on R3, and the crenulation and
protrusion of outer peristome, show large intraspecific
variability (although they can be useful in some cases to
distinguish species). The new species described here are
recognized based on the following characters (Table 2):
(1) Dicharax burchi sp. nov. is recognized by its conical

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18

shell shape with an elevated spire, even if the examined
populations show variation in terms of rib strength and
density, the shape of R3 swelling and the expansion of
the outer peristome; (2) Dicharax panhai sp. nov. has a
unique shell shape of a wide base and triangular dorsal
side, and a short R2; (3) Dicharax pongrati sp. nov. has
a lenticular, depressed-conical shell shape, an extreme-
ly long R2 and a very short R3; (4) Dicharax borealis
sp. nov. has a depressed-conical shell shape, a very low
and elongated R3 swelling and an inner peristome with
three very shallow indentations. Although D. borealis sp.
nov. could be interpreted as a D. cucullatus with a low
R3 swelling, it is sympatric with a D. cucullatus popu-
lation at the type locality of D. borealis sp. nov., which
excludes conspecificity.

One population of D. cucullatus from Doi Ang Khang,
Chiang Mai Province, Thailand exhibits the spiral stri-
ation on R1 (Fig. 2C, D). The spiral striation was rare-
ly found in Dicharax and was reported in very few
species (e.g. D. candrakirana Nurinsiyah & Hausdorf,
2017, one population of D. depressus). In those cases,
the spiral striation is probably the part of lower shell
layers and assumed not to be homologous with those of
Chamalycaeus and Metalycaeus species (Pall-Gergely et
al. 2017, 2020b). However, in this case the normal spiral
striation which is elevated from the shell surface found in
one D. cucullatus population could be regarded as homol-
ogous to the condition found in the other genera.

The variation on the exterior sculpture of the oper-
culum has been rarely recorded. Foon and Liew (2017)
noted the discrepancy of the operculum of two spe-
cies, Stomacosmethis roebeleni (Mollendorff, 1894)
and Pincerna thieroti (Morgan, 1885), between the
original description and recently examined specimens.
The original descriptions of both species described the
opercula as entirely non-calcified (Morgan 1885, Mol-
lendorff 1894), while the recently examined specimens
exhibit the opercula with calcified exterior layers (Foon
and Liew 2017). Moreover, Pall-Gergely et al. (2017)
reported the variation from an operculum without el-
evated lamella to the presence of elevated lamella in
D. cristatus, D. depressus and D. fimbriatus, and from
smooth to multispiral (1.e. with low lamella) opercula in
D. fraterculus (Bavay & Dautzenberg, 1900). Howev-
er, these differences were compared between specimens
from different localities. The only report about variation
(presence or absence of the elevated lamella) within the
same population was reported in Metalycaeus nippon-
ensis (Reinhardt, 1877) (Pall-Gergely et al. 2020b).
Here we first report the variation of the outer opercular
surface in the same population in Dicharax, which is
illustrated in D. notus in possessing an operculum ei-
ther without (Fig. 7A) or with an elevated lamella (Fig.
7B). We thus suggest that this trait might be less advan-
tageous in diagnosing different Dicharax species, and
probably in other alycaeid genera.

The body coloration of living specimen has been
scarcely reported compared to the shell color. Living
specimens of both D. cucullatus (Fig. 5A) and D. notus

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Parin Jirapatrasilp et al.: Micro land snail Dicharax in Thailand

(Fig. 5B) have a reddish orange shell with a pink apex
and a light-yellow to pale orange body coloration. In ad-
dition, most Dicharax shells in this study have a reddish
orange shell (Fig. 6). Comparing to other alycaeid spe-
cies, Stomacosmethis somnueki (Panha & Patamakan-
thin, 2001) has a white, bright yellow or orange shell
and a pale yellow body color (Panha and Patamakanthin
2001), whereas several species of Alycaeus, Pincerna and
Stomacosmethis species from Peninsular Malaysia have
a yellow shell with an orange apex and a pale yellow to
gray body color (Foon and Liew 2017). The shell col-
oration could be used to classify some alycaeid genera
to some extent. Stomacosmethis is usually bright yellow
or orange, and A/ycaeus is more colorful with reddish or
yellowish tint compared to Chamalycaeus which has a
similar shell but colorless (Pall-Gergely et al. 2020b).
However, the light-yellow to pale orange body coloration
is common, often associated with lighter colored shell
and might not be different among genera.

Acknowledgements

The authors are grateful to all members of the Animal Sys-
tematics Research Unit members, Chulalongkorn Univer-
sity for their kind help during field trips in Thailand, and
especially to S. Panha, J.B. Burch and P. Dumrongrojwat-
tana for the collections from northern Thailand. We are
also indebted to J. Ablett, F. Naggs and H. Taylor (NHM,
London) and R. Janssen, K.-O. Nagel and S. Hof (SMF,
Frankfurt) allowing the authors to examine the material
housed in the type collections, the type material database
and photographs. We also thank D.G. Herbert, J.K. Foon
and F. Kohler for their valuable comments that greatly
improved the manuscript. This project was mainly fund-
ed through grants received from the Thailand Research
Fund, TRF-DPG628001 and TRF-DBG6080011, Centre
of Excellence on Biodiversity, Chulalongkorn Universi-
ty, BDC-PG2-161002, and supported by the 2020 Post-
doctoral Scholarship, Rachadapisek Sompote Endow-
ment Fund, Chulalongkorn University, to PJ. BP-G was
supported by the Hungarian Research Fund (OTKA FK
135262) and the Janos Bolyai Research Scholarship of
the Hungarian Academy of Sciences.

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