New species of terrestrial molluscs (Caenogastropoda, Pupinidae & Pulmonata, Vertiginidae) of the Hon Chong – Ha Tien limestone hills, Southern Vietnam

2007·0.86 MB·English

by  Vermeulen, J J

BASTERIA, 71:81-92,2007
Newspecies ofterrestrialmolluscs
(Caenogastropoda, Pupinidae &Pulmonata, Vertiginidae)
oftheHon Chong - HaTien limestonehills,SouthernVietnam
J.J. Vermeulen
Nationaal Herbarium,Leiden Branch,P.O.Box 9514,NL2300 RALeiden,The Netherlands
PhungLeCang
BiologyFaculty,the University ofNaturalScience,227NguyenVanCu Quan,5Hochiminh,City,
Vietnam
TruongQuam+Tarn
InstituteofTropicalBiology,85TranQuocToan Quan,3Hochiminh City,Vietnam
Small limestone hills between the towns ofHon Chong and Ha Tien (Kien Giang Prov.,
Southwestern Vietnam) harbour a fauna of65 species terrestrial molluscs, ofwhich 36 are
assumed tobeendemic tothehills. Some occuronmosthills ofthe group,others onafew,or
evenonasinglehill only.Eightendemic taxa,newto science, aredescribed here:3species of
thenewgenusNotharinia (Pupinidae),viz.N. attenuata,N.breviorand N. crassilabris,and 5taxa
ofthe familyVertiginidae,viz. Acinolaemuscarcharodon,Anauchen informis informis, Anauchen
informisparcedentata,Aulacospiraconica,andMontapiculuspyramidalis.
Key words: Vietnam, Kien Giang Province, Hon Chong, Ha Tien,Pupinidae, Notharinia,
Vertiginidae,Acinolaemus,Anauchen,Aulacospira,Montapiculus.
INTRODUCTION
TheSouthwesternpartof theMekong delta(Vietnam, Southwesternpart) consistsof
boundlessplains with hereand thereanisolatedrocky hill. A string ofsmall andmedi-
um-sizedhillsstretchingalongthecoastbetweenHonChong andHaTienconsistoflime-
stone;seemap 1.Thegeomorphological history ofthesehillshas determinedthenature
ofthelocallandsnailfauna.Theinlandhillsarenow surroundedby agricultural land on
clayey soil, only afewofthemoreseawardonesstillhaveafringeof mangroveswamps
surrounding them.Thepresenceofnofewerthanthreelevelsofundercutting atthebase
of thelimestonehills(theupperabout2.5m, thelowermostandbyfar deepestabout 0.8
mabovethepresenterosionbasis,indicatesthatthehillshavebeensurroundedby water,
mostlikelytheseaor,atleast,byacoastalfadesincluding mangroves,i.e.an environment
definitelyinhospitable tomostformsoflandlife, fora considerableperiod oftimeinthe
past. Italsoshowsthat thearea asawholehasbeenuplifted withrespecttothesealevel
during itsrecent geomorphogical history, presumably ascompensation ofongoing subsi-
denceinthenearby Mekong delta, amajorsedimentarybasin.
82 BASTERIA,Vol. 71, No. 1-3, 2007
Map1.Mapofthe HonChong-HaTienarea,KienGiangProv.,SouthernVietnam;limestone hillsindi-
catedinblack;a, HaTien;b, Hon Chong;1,Hon ChongHill;2,Ba Tai Hill;3,Son Cha Hill; 4,BaiVoi
Hill;5,ThachDongHill;6,DaDungHill. Upperright:MapofVietnam,withareaunderstudyindicated.
Geographically, thelimestonehills are isolated fromotherlimestonehills. Infact they
form the south easternmost extension of a small belt of limestone hills in adjacent
Kampuchea. The distancebetween this belt and other limestonehills in Kampuchea is
considerable.InVietnam, thenearestlimestoneoccurs severalhundredsofkilometersto
thenortheast.
Vermeulenetal:. New species ofterrestrialmolluscsfromSouthernVietnam 83
Very little, if any, pristine vegetation is left onthe limestonehills. Themostmature
vegetation is foundnearHonChong andHaTienvillage, onhillsthatareusedasplaces
of worship; the temples evidently provide some protection against destructiveexploita-
tion ofthehill.The environmentonthehills, duetoboththeproximity oftheseaaswell
asto humanimpact, must always havebeen dynamic; theword'pristine' maynot appli-
cablehere.
Human impact is various:smallscaleagriculture, silviculture andshrimp farming at
thefootofthehillsand in atleastoneofthedolines, firewoodcollecting, various usesof
the caves, invasion of alien species, and lastbut not least, war damage. Bombing has
causedanextensivesuperficial spallingofthekarstifiedrock surfaceover alargeareasur-
rounding theactualblasts.
At present, most of the limestone hills, those with temples nearby excepted, are
sparsely vegetated with evidently secondary herbaceousand low woody growth and
grass.Higher andmorematurewoody vegetationcanbefoundin deep cleftsand depres-
sionsinthe rockand, inparticular, in severallarge dolines.
Isolation determinedthe nature of the local biodiversity. Geographical isolation,
because thenearest limestonehills are milesaway, andenvironmentalisolationbecause
they havebeen,andstillare, surroundedbyanenvironmenthostiletomanyformsofland
life. Environmentalpressure occurred when periods during which the limestonehills
were landlockedandshelteredfromtheelementstookturns withperiods during which
thehills wereexposed to seawinds, droughtandsaltspray.
As aresult, theterrestrialmolluskfaunaofthehillscanbe characterizedasanisland
fauna:itcomprises only65 species, whichis notmuchwhencompared tootherlimestone
areasin SEAsia,butthenumberofspecies markedas probably endemictotheareais36,
or 55%.Thisis a very highratio indeed,and itmakesthebiodiversity valueof thefauna
considerable.Someoftheseendemicshavearangerestricted toonly oneor afewhillsof
thegroup.
Altogether 30 species (46%) cannot be identifiedto species level; most of thesewill
prove to be newto science. Investigations intothe faunaare ongoing, but we feel that
earlypublication of some ofthese noveltieswillhighlight the special nature of thelocal
fauna.
The drawings havebeenmadeby thefirstauthor, withtheaid ofa WildM8stereo
microscopewitha cameralucidadevice.
SYSTEMATICPART
Pupinidae L.Pfeiffer, 1853
Nothariniagen.nov.
Typespecies:Notharinia attenuataspec. nov.
Description. - Shellwhite,ratherthin,aboutopaque,dextral. Spireaboutcylindrical.
Whorls4 1/8-51/2.Top whorlsslightly oblique. Protoconchsmoothat40xmagnification.
Teleoconch:Radialribs present,orthoclineorslightly prosocline, straightor sinuous,low,
withasingle crest. Spiral sculpture absent. Nointernalconstrictionpresentin thespire,
nearthe aperture. Umbilicus closed. Planethrough aperture about parallel withcoiling
axis; aperture aboutcircular, without abasal edge, without teeth. Peristomesimple or
double,not or hardly extendedover the previous whorlon theparietal side, withouta
84 BASTERIA, Vol. 71, No. 1-3, 2007
Figs 1-3.Notharinia spec. 1, N. attenuata spec. nov.; a, holotype (shell height2.0 mm), Vietnam,Hon
Chong,HonChongHill (RMNH), frontal view;b,paratypefrom samelocality(V), right lateralview.2,
N. breviorspec. nov.; a,holotype (shellheight1.7mm),Vietnam,Ha Tien,Thach Dong Hill (RMNH),
frontalview;b,paratypefromsamelocality(V), rightlateral view.3,N.crassilabris spec. nov.;a,holotype
(shell height 2.1 mm), Vietnam, Ha Tien, Thach Dong Hill (RMNH), frontal view; b, paratype
from samelocality (V),rightlateralview.
Vermeulenet at:Newspecies ofterrestrialmolluscsfromSouthernVietnam 85
well-demarcatedlip onthepalatal andbasalside. Shellheight 1.5-2.05mm. Operculum
not seen.
Distribution.- Endemictosouth-westernVietnam,KienGiangProv., scatteredsmall
limestonehills close to the borderwithKampuchea, betweenHa Tien and HonChong.
Three species known.
Ecology. - Small, isolatedlimestonehillsincoastalplains onclay soil, nowmainly
dryland in use forvarious purposesbutoriginally atleastpartly withinthetidalzone.
ThehillswhereNothariniaoccurs haveapredominantly woody vegetation. Theclimateis
strongly seasonal,withprolonged dryperiods. Presumably, thesnailsare soildwellers.
Notes. - The generic description is made tosetthegenusapartfromsimilargenera
of the Diplommatinidae as wellas thePupinidae. Atfirst sight, Nothariniais of typical
diplommatinid appearance;and its species would fit particularly well into the genus
AriniaH. & A.Adams, 1856.However,allDiplommatinidae havea circularconstriction
deep insidetheultimatewhorlorevenin thepenultimate whorl,onwhichreststhesmall,
circular operculum. Sucha structure isabsent inNotharinia,and thereforewe prefer to
include the genuselsewhere. Although nooperculum has beenseen, we assume that
Nothariniais aprosobranch, andwefindmostsimilarformsinthePupinidae, inthegenus
Pseudopomatias Von Moellendorff, 1885.NothariniadiffersfromPseudopomatias in being
much smaller (1.5-2.05 mm versus 5.5-14 mm high) and in having a cylindrical shell
(rather thanconicalorfusiform).
Nothariniaattenuata spec.nov.(fig. 1)
Material seen.-Vietnam,Kien GiangProv.,KienLuong,HonChongHill(V9993/11,incl.holotype
RMNH 108981).
Description. - Shellcylindrical butusually somewhatattenuatedtowardsthe aper-
ture, top widely rounded to somewhat truncated. Whorls 5-5 3/8, convex. Suture
impressed. Radialribs straight, distinct, ratherlow and thin, densely placed; butslightly
sinuous,particularly atbothends, onthebodywhorlsand particularlyonthelastwhorl,
andusually slightly widerspaced onthelastwhorl.Umbilicusclosed, lastwhorltightly
coiledso thathardly anaxial depression is left.Last whorlslightly expanded closetothe
aperture. Peristomesimple, somewhatthickenedand somewhatreflexed; parietal side
fusedto the previous whorl. Height 1.7-1.9 mm; width (excl. last whorl) 0.75-0.85 mm;
index(height/width) 2.20-2.26. Height aperture0.45-0.5 mm;widthaperture0.45-0.5mm.
Distribution.- Vietnam,SW. part, asingle limestonehill nearHonChong. Proposed
IUCN ThreatCategoryVulnerableVU D2 (IUCN2001 Categories & Criteria, v.3.1); some
environmentalprotectionis provided bythefact thattheaplace ofworship ispresenton
theflankof thehill.
Nothariniabreviorspec. nov. (fig. 2)
Material seen.- Vietnam, KienGiangProv., HaTien,ThachDongHill(V 11468/7,incl. holotype
RMNH 108983).
Description. - Shellshortly cylindrical, sometimesslightly bulgingabouthalf-way its
length, top widely rounded to somewhattruncated.Whorls4 1/8—4 1/2, (moderately)
convex. Suture(moderately) impressed.Radialribs straight, distinct, ratherlowandthin,
86 BASTERIA,Vol. 71, No. 1-3,2007
(very) densely placed, usually slightly widerspaced onthelastwhorl.Umbilicusclosed,
but last whorlloosely coiled so that an axial depression is present. Last whorl slightly
expanded close tothe aperture. Peristomedouble; outerperistome somewhatspreading
beyond the inneron the palatal andbasal side; inner hardly to moderately protruding
from the outer, somewhatthickenedand somewhatreflexed; parietal side fused to the
previous whorlforashortdistanceonly; tracesof densely placed radiallamellaepresent
betweentheouter antheinner peristome. Height 1.5-1.6mm;width(excl.lastwhorl)0.85-
0.9mm,index(height/width) 0.85-0.95.Height aperture0.5-0.55mm;widthaperture0.55-
0.65mm.
Distribution. - Vietnam, SW. part, a single minute limestone hill near Ha Tien.
Proposed IUCN ThreatCategory VulnerableVU D2 (IUCN2001Categories & Criteria,v.
3.1); someenvironmentalprotection is provided by thefact thatthea place ofworshipis
presentonthetopof thehill.
Notes. - Differs fromN. attenuata in having a shortly cylindrical spire withfewer
whorls,and inthemoreloosely coiledlastwhorlthat,although itsealsofftheumbilicus,
stillleavesashallowaxialdepression. Theperistome isdouble,buttheinner isbarelypro-
truding fromtheouter in someshells.
Nothariniacrassilabrisspec. nov. (fig.3)
Material seen.- Vietnam,Kien GiangProv.,HaTien, ThachDongHill (V11467/>10,incl.holotype
RMNH 108984);HaTien,DaDungHill(V11444/>10).
Description. - Shell cylindrical, rarely withaslightly widened topwhorl, top(wide-
ly)rounded.Radialribs about straight,ratherlow,thinand rather densely placed onthe
topwhorl,increasingly sinuous, somewhathigherandmore widely spaced towardsthe
aperture, widely spaced and distinctly sinuousonthelast 1/2whorl.Umbilicusclosed,
last whorl tightly coiledso that hardly an axial depression is left. Last whorl slightly
expanded close to the aperture. Peristome double; outer peristome usually somewhat
spreading beyuond theinneronthepalatal andbasalside;innerperistome moderately to
distinctlyprotruding fromthe outer, somewhatthickenedand somewhatreflexed;pari-
etalsidefused totheprevious whorl; densely placed radiallamellaepresentbetweenthe
outer anthe inner peristome. Height 1.6-2.05mm;width(excl. last whorl)0.65-0.75mm,
index(height/width) 2.46-2.73. Height aperture0.5-0.6mm;widthaperture0.5-0.55 mm.
Distribution.- Vietnam, SW. part, two limestonehillsnearHa Tien. Proposed IUCN
Threat CategoryVulnerableVU D2 (IUCN2001 Categories&Criteria, v. 3.1); some envi-
ronmentalprotection is provided bythefactthattheaplace ofworship ispresentonboth
hills.
Vertiginidae Fitzinger, 1833
AcinolaemusThompson& Upatham, 1997
Notes. - The species described below does not fully meet the diagnostic set for
Acinolaemusasgivenby Thompson andUpatham (1997: 223):itlacksthe spiral sculpture
of theprotoconch, and has adownwardsturnedlastportion ofthelastwhorl.However,
itssculpture andthedentitionin the apertureare typicalforthegenus.
Vermeulenetal.:Newspecies ofterrestrialmolluscsfromSouthernVietnam 87
Acinolaemuscarcharodonspec.nov.(fig.4)
Material seen.- Vietnam, KienGiangProv.,KienLuong,HonChongHill (V 11320/>10,incl. holo-
typeRMNH108985);nearHonChong,BaTaiHill(V9966/>10);nearHonChong,BaiVoiHill,Nand NW
flank(V11296/6);do.,dolinealongEastflank(V11260/1);do.,HangTiencave, shrubland (V 11326/6);do.,
HangTiencave, below doline (V10024/6).
Description. - Shell white,ratherthin, somewhattranslucent, dextral. Spire discoid
butwith thefirstwhorls protruding, conical, andwith thelastportion of thelastwhorl
abruptly curvedobliquely downwards,formingashort, freetube.Whorls4 1/4-43/4,the
inner convex, theouterflattenedaroundtheperiphery, shoulderedabove,morerounded
below, suture deeply impressed. Protoconch dull, without spiral threads. Teleoconch
shiny; aradialsculptureof very fine, densely and regularlyplaced riblets; aspiral sculp-
ture of rather distinct, rather well-spaced spiral threads. Umbilicus open, very wide.
Peristome entirely free, general outline triangular with rounded edges, somewhat
reflexed, thin. Aperture with4lamellae:1 shortand high parietalis deep inside; 1 long
angularis startingattheperistome, gradually lowerinsidebutwithwithanantrorse,nee-
dle-sharp toothattheleveloftheparietalis; 1 ratherlong, sigmoid palatalis starting near
the peristome and deeply notched about half-way, so that insome shellsthis lamellais
almostdividedintotwo;1 ratherlong basalisstartingneartheperistome asashort, high
lamella,separated by a deepandwidenotchfromanantrorse,needle-sharp toothfurther
inside.Height 1.2-1.4mm(0.9-1.05mm withoutthedownwardspointing partofthelast
whorl);width1.5-1.8mm. Height aperture0.5-0.6mm;widthaperture0.55-0.65 mm.
Distribution.- Vietnam, SW. part, two limestonehills near Hon Chong. Proposed
IUCN Threat Category VulnerableVU A4 D2 (IUCN 2001 Categories & Criteria, v.3.1);
BaiVoi Hillis slatedforlimestonemining;but atHon Chong Hillsome environmental
protection isprovided by thefact thattheaplaceof worshipispresentontheflankofthe
hill.
Notes.- Thedownwardscurvedfreeportion ofthelastwhorl suffices to distinguish
A. carcharodonfromotherspecies ofthegenus.
AnauchenPilsbry, 1917
Anaucheninformis spec. nov. (figs 6, 7)
Anaucheninformis informis subspec. nov.(fig.6)
Material seen.- Vietnam,Kien GiangProv., Kien Luong,HonChongHill (V9999/3);nearHon
Chong,Bai VoiHill(V9939/>10);do.,dolinealongEastflank(V11258/>10,incl.holotypeRMNH108986);
do.,North and Northwestflank (V11295/1);do.,HangTien cave,below doline (V10023/3).
Description. - Shell darkreddishbrown, ratherthin, opaque, dextral. Spire ovoid-
conicalto conical with slightly convex sides. Whorls 43/8-5 3/8, convex, well rounded,
suture deeply impressed. Protoconchshiny, withregularly and widely spaced, thinspiral
threads.Teleoconchdull;aradialsculptureofirregularly spaced growth lineswhichmay
be slightly raised towardsthe sutures; a spiral sculpture of fine, wavy, irregularly and
rather widely spaced threads, particularly present on the lower half of the whorls.
88 BASTERIA,Vol. 71, No. 1-3,2007
Figs 4-5. 4,Acinolaemus carcharodon spec. nov.; a,holotype(shellheight1.15 mm,incl. tuba), Vietnam,
KienLuong,Hon ChongHill (RMNH), frontal view;b,paratypefrom samelocality (V),umbilical view;
c,paratypefrom samelocality (V), right lateral viewwith shell wall partly removed;d,paratypefrom
samelocality(V),frontalview ofaperture.5,Montapiculuspyramidalisspec.nov.;a,holotype(shellheight
1.7mm,incl.tuba),Vietnam,KienLuong,HonChongHill (RMNH), frontalview;b,paratypefromsame
locality (V),umbilical view; c,paratypefrom samelocality(V), frontalviewofaperture.
Vermeulenetal.: New species ofterrestrialmolluscsfromSouthernVietnam 89
Umbilicusopen,narrow, deep. Peristomeattachedtotheprevious whorl, generaloutline
aboutsubrectangular butwitharounded lowermargin,somewhatexpanded onthepari-
etal side, reflexed elsewhere, thin.Aperture with 3-5 lamellae: 1 distinct parietalis, 2
palatales, theuppersometimesmissing, withorwithout1basalis, 1 distinctcolumellaris.
Height 3-4mm;width2.2-2.7 mm. Height aperture 1.3-1.5mm; widthaperture 1.2-1.5
mm.
Distribution. - Vietnam, SW. part, threelimestonehills nearHon Chong. Proposed
IUCN ThreatCategory VulnerableVU A4D2 (IUCN2001 Categories & Criteria, v. 3.1);
BaiVoi Hillis slated forlimestonemining;but atHon Chong Hill someenvironmental
protection isprovided by thefactthattheaplaceofworship ispresentontheflankofthe
hill.
Notes.- Amongsimilargenera,Anauchenis characterizedby theabsenceof anangu-
lar tooth.Mostspecies haveaslender, conical spire,oftenwithconcave sides,except for
A. angthongense Burch & Panha, 2000,whichapproaches A. informis in shape. Thelatter
differsinhavingaperistome ofmoreangular outline,less dintinctly flaringandless well-
rounded ontheparietal andpalatal side.
Anaucheninformisparcedentata subspec. nov. (fig.7)
Material seen.- Vietnam.KienGiangProv., KienLuong,Ba TaiHill (V9956/>10, incl. Holotype
RMNH 108987);do., onshore ofsurrounding tidal lake (V 9984/3);do.,fossil depositin rock cleft (V
11499/>10).
Description. - Like the nominotypical subspecies, but whorls 5 1/8-53/8, aperture
with1-3 lamellae:1 distinctparietalis, 2palatales, sometimestheupperorbothmissing.
Height 4-4.6 mm; width 2.7-3 mm. Height aperture 1.6-2.2 mm;width aperture 1.6-1.7
mm.
Distribution. - Vietnam, SW. part, one limestonehill near Hon Chong. Proposed
IUCN ThreatCategory VulnerableVU D2 (IUCN2001 Categories & Criteria,v. 3.1); the
hillhasnoprotected status atpresent,buthasnotyetbeenearmarkedformining.
Notes.- Somewhatlarger thanthetypesubspecies andwithfewerand less distinct
apertural teeth.Diagnostic is the absence ofthe columellaris, atmostatiny gibbosity is
presentin someshells.
Thefossil depositin whichthespecies was foundhasnotbeendated.
Aulacospira VonMoellendorff, 1890
Aulacospira conica spec.nov. (fig. 8)
Material seen.- Vietnam.KienGiangProv.,HaTien, ThachDongHill (V11464/5,incl.Holotype
RMNH 108988);Ha Tien,DaDungHill (V11431/7).
Description. - Shelldark reddishbrown, ratherthin,opaque, dextral. Spire conical
withaboutflat sides.Whorls33/8-3 1/2, distinctlyshouldered, concave abovetheshoul-
der, flattenedbelow,aroundtheperiphery, suture deeply impressed. Protoconchmoreor
less shiny, withoutany spiralsculpture. Teleoconchdull; aradialsculpture ofirregularly
spaced growth lineswhichmaybeslightly distinctlyraisedatirregularintervals; nospi-
90 BASTERIA, Vol. 71, No. 1-3,2007
Figs6-8.6,Anauchen informisinformis subspec.nov.,holotype(shellheight3.4mm),Vietnam,nearHon
Chong,BaiVoi Hill (RMNH), frontal view. 7,Anauchen informisparcedentatasubspec. nov.; a,holotype
(shellheight4.5mm),Vietnam,KienLuong,Ba TaiHill (RMNH), frontal view;b,paratype(shellheight
3.6 mm)from same locality (V), frontal view. 8, Aulacospira conica spec. nov., holotype (shellheight
2.5mm),Vietnam,Ha Tien,ThachDongHill(RMNH), frontal view.