Four new Diplommatinidae (Gastropoda, Prosobranchia, Diplommatinidae) from southern Thailand and northern Peninsular Malaysia

6 Pages·2001·1.3 MB·English

by  Maassen, Wim J M

BASTERIA, 65:51-56, 2001
FournewDiplommatinidae (Gastropoda, Prosobranchia,Diplommatinidae) from
southernThailandandnorthernPeninsularMalaysia
Wim+J.M. Maassen
Nationaal Natuurhistorisch Museum,RO. Box9517, NL 2300RALeiden, The Netherlands
Four new species ofthe terrestrial,prosobranch family Diplommatinidaeare described.
Opisthostoma(Plectostoma)sinyumensisspec. nov.and O.(P.) christaespec.nov. areboth reported
from Peninsular Malaysia. Arinia panhaispec. nov. is described from Thailand and A.jensi
spec. nov.from Peninsular Malaysia. These arethe firstrecords foranArinia species from
Thailand andPeninsular Malaysia.
Key words: Gastropoda,Prosobranchia,Diplommatinidae,Arinia,Opisthostoma, Plectostoma,
taxonomy,Peninsular Malaysia, Thailand.
INTRODUCTION
Two samples withunidentifiedDiplommatinidae, collectedby Mr. andMrs. Hemmen,
Wiesbaden, in southernThailandand northernPeninsular Malaysia, werereceived for
identification.Thematerialproved tobelong to threespecies.
Asearchfordescriptions inthe relevant literature,in particularVan BenthemJutting
(1952,1961), Kobelt(1902), andVermeulen(1996), failedand,therefore,these species are
considerednew to science. According to the identificationkeys published by Kobelt
(1902: 378) and Vermeulen(1996: 90) they shouldbe classified with the genusArinia.
However, VanBenthemJutting (1952: 49), on thebasis ofa single sample, described a
species fromPeninsularMalaysia, thatshares someoftheconchological characterswith
our three new species, as Opisthostoma (Plectostoma) umbilicatum. According to Van
BenthemJutting (1952: 51): "The general architecture and inconspicuous deviationin
the last whorl, however, place it in Opisthostoma”. In a later publication, Van Benthem
Jutting(1961: 39) mentionedan additionalrecord from "Gunong Sinyum, Pahang" for
O. (P) umbilicatum. Both samples are in the Zoological Museum (Amsterdam). While
comparing the specimens, it turnedoutthat these are not conspecific. The shells from
Gunong Sinyum representanadditionalnew species.
The generic assignment ofthese species is problematic. Theirshellsdo not showthe
sinistroidcoiling (Gittenberger, 1995:19) ofthe lastwhorl,whichis supposed tocharac-
terize Opisthostoma. Sincein two of the newspecies the tubaofthe shells shows a slight
deviation, however, I provisionally accept for those species the generic name
Opisthostoma, following Van Benthem Jutting. The subgenera Opisthostoma s.s. and
Plectostoma are in use forspecies with relatively small (shells less than2 mm broad or
high) and larger shells, respectively. Two of the new species are not classified in
Opisthostoma as they are regularly dextraland donot showany traceof deviationofthe
lastwhorl.These species are provisionally consideredtobelong tothegenusArinia.For
additionaldataonthevarious,poorly defined,genus-groupnominaltaxa,seeVermeulen
(1996).
52 BASTERIA, Vol. 65,No. 1-3, 2001
Abbreviations for shell characters: B, shell width; H, shell height. For collections:
RMNH, NationalMuseumof Natural History (formerly Rijksmuseum van Natuurlijke
Historie), Leiden; HW, J. & C. Hemmen, Wiesbaden; CUIZM, Chulalongkorn
University Zoological Museum, Bangkok; ZMA, Zoologisch Museum, Universiteit van
Amsterdam,Amsterdam.
SYSTEMATICPART
GenusOpisthostomaW.T.&H.Blanford, 1860.Typespecies: O.nilgiricumW.T.& H.Blanford,1860 (India)
Subgenus PlectostomaH.Adams, 1865. Typespecies:P. decrespignyiH.Adams, 1865 (Borneo).
Opisthostoma (Plectostoma) sinyumensis spec. nov. (figs 1, 6-7)
Material. — Pensinsular Malaysia,Pahang, GunongSinyum; vi.1954; M.W.F.Tweedie leg., ex. Raffles
Museum,Singapore (ZMA/holotype;ZMA/58paratypes, RMNH 81804/2 paratypes).
Description. — Shell dextral, ovoid, light brown, shining and transparent; with 5.5
distinctlyconvex whorls,separated byarather deepsuture,andprovided withadistinct,
very fine, spiral striation.Lastwhorl aboutasbroadas thepenultimate one. Radialribs
rather thin, increasingly higher and sharper on the lower whorls; on the penultimate
whorl 7-8ribs/mm, abovethe aperture 8-9 ribs/mm. Theconstriction consists only ofa
transversalthickening onthepalatal side ofthebody-whorl. Thetubais0.75whorllong
and turns off slightly inwards. Umbilicus very narrow. Peristome double; the inner
peristome protruding distinctly from theouter one.Infrontalview,the aperturetouches
the middle of the previous whorl and is hardly turned downwards. Operculum
unknown.
Dimensions:H 1.9-2.2mm; B 1.2-1.3mm.
Derivationominis.— Namedafterthe typelocality Gunong Sinyum.
Remarks. — Thespecies is very similarto O. umbilicatumVanBenthemJutting, 1952,
butitsshellshaveonewhorllessandare smaller(O. umbilicatum, H2.8-3.1mm;figs 2,8-
9)andslender ovoidinsteadofturreted.
Opisthostoma (Plectostoma) christae spec.nov.(figs 3, 10-11)
Material. — Peninsular Malaysia,Kelantan,road 8Gua Musangto Machamg,right side offkm 24.9;
04°55'022"N, 102°06'934"E;J. &C. Hemmen (MAL 162/00)leg.(RMNH 81805/holotype, 81806/1 para-
type;HW/20paratypes).
Description. — Shell dextral, high conical, reddishbrown, shining andtransparent;
with5.75 distinctly convex whorls, separated by arather deep suture,and withoutaspi-
ral striation. The lastwhorl is wider thanthe penultimate one. Radialribs ratherthin,
increasingly muchhigherand sharper onthe lowerwhorls; onthe penultimate whorl5-
6 ribs/mm, above the aperture with5-6ribs/mm. Theconstriction consists ofa trans-
versal thickening all around, andasmall and low, longitudinal tubercle at the angular
edge, just entering the transversal thickening. The tuba is 0.5 whorl long and hardly
turns offinwards. Umbilicus very narrow. Peristomedouble; the inner peristome only
slightly protruding from the outer. In frontal view, the aperture touches the previous
Maassen:FournewDiplommatinidae 53
Figs 1-5. 1,Opisthostoma(Plectostoma)sinyumensis spec. nov.,paratype,Peninsular Malaysia,Pahang,Gunong
Sinyum.2,Opisthostoma(Plectostoma)umbilicatumVanBenthem Jutting,1952,paratype,Peninsular Malaysia,
KotaTongkat. 3,Opisthostoma(Plectostoma)christae spec.nov.,paratype,Peninsular Malaysia, Kelantan,road
8GuaMusangtoMachamg,rightsideoffkm24.9.4,Ariniapanhaispec.nov.,paratype,Thailand,Yalaprov.,
KachongCave.5,Arinia jensispec. nov.,paratype,Peninsular Malaysia,Kelantan,road 8Gua Musangto
Machamg,rightside offkm 24.9.Scalebar 1mm.
whorlattheright ofthemiddleandishardlyturnedupwards. Operculumwithadistinct
spiralridge onits outer surface.
Dimensions: H2.7-3.1 mm,B 1.7-2.5mm.
Derivationominis.— Namedaftermy friendChristaHemmen,whofoundthisspecies.
Remarks. — From the conchologically most similar species O. umbilicatumit canbe
distinguished by the absenceofaspiral striation, themore convex whorls, the different
attachmentofthe aperture,andtheshorter tuba.
GenusAriniaH.&A.Adams,1856.Type species: Cyclostoma minus G. B.Sowerby, 1843
(Philippines).
54 BASTERIA, Vol. 65,No. 1-3, 2001
Figs 6-11. Opisthostoma(Plectostoma) spec. 6-7, O. (P.) sinyumensis spec. nov., paratype, Peninsular Malaysia,
Pahang,GunongSinyum,actual height2.27mm. 8-9,O.(P.)umbilicatumVan BenthemJutting, 1952, paratype,
Peninsular Malaysia,KotaTongkat,actualheight3.0 mm. 10-11, O.(P.)christaespec. nov.,paratype,Peninsular
Malaysia,Kelantan,road 8Gua MusangtoMachamg,rightsideoffkm 24.9,actual height3.13mm.
Maassen:FournewDiplommatinidae 55
Figs 12-15.Arinia spec. 12-13,A.panhaispec. nov., paratype,Thailand,Yala prov., KachongCave, actual
height2.73 mm. 14-15,A.jensispec.nov., paratype,Peninsular Malaysia,Kelantan,road 8 GuaMusang to
Machamg,rightsideoffkm 24.9,actual height2.67mm.
Ariniapanhai spec. nov. (figs 4, 12-13)
Material. — Thailand, Yala province, Kachong Cave, 2.6 km offkm 45.7 road 410 (Yala Bretong);
06°55'022"N,101o12'160"E; 4.X.2000; J.& C.Hemmen (TH88/00) leg. (RMNH80809/holotype,81810/2
paratypes;CUIZM/2paratypes;HW/45paratypes.
Description. — Shelldextral, conical, lightbrown, shining andtransparent; withsix
moderately convex whorls, separated by a deep suture,and with adistinct spiral stria-
tum.Thepenultimate whorlslightly widerthanthebody-whorl. Radialribs ratherthin,
increasingly higher and sharper on the lower whorls; onthe penultimate whorl 6-8
ribs/mm,above theaperture7-8ribs/mm. Theconstrictionconsists ofatransversal thic-
kening allaround,and of asmallbut distinct, longitudinal tubercle attheangular edge,
just entering the transversal thickening. The tuba is 0.7 whorllong. Umbilicus widely
open,eccentric, showing part ofthe penultimate whorl. Peristome doubled,the inner
peristome only slightly protruding from the outer.The apertureis situated to the right
ofthemiddleofthe previous whorlandclearly turnedupwards. Operculum corneous,
withadistinct spiral ridge onitsouter surface
Dimensions: H2.5-2.7mm,B 1.9-2.2mm.
56 BASTERIA, Vol. 65,No. 1-3, 2001
Derivationominis.— Namedaftermy friendDr. SomsakPanha,Bangkok.
Remarks. — See theremarks withthe next species.
Ariniajensi spec. nov. (figs 5, 14-15)
Material. — Peninsular Malaysia,Kelantan,alongrightsideofroad 8 fromGuaMusangtoMachamgat
rkm24.9;04°55'022"N,102°06'934"E;J.&C.Hemmen (MAL162/00)leg.(RMNH81807/holotype,81808/2
paratypes; HW/250 paratypes)
Description. — Shelldextral, ratherlowconical, lightbrown,shining andtransparent;
with 5.5 distinctlyconvexwhorls, separated by arather deep suture,andwithout aspi-
ralstriation.Thebody-whorl iswiderthanthepenultimate whorl.Radialribs ratherthin,
increasingly muchhigherandsharper onthelowerwhorls; onthe penultimate whorl4-
6 ribs/mm, abovethe aperture with 4-6 ribs/mm. The constrictionconsists ofa trans-
versal thickeningallaround,andofasmallandlow,longitudinal tubercleattheangular
edge,justenteringthetransversalthickening. Thetubais0.5whorllong. Umbilicusnar-
row. Peristomeflaring, doubled,the inner peristome only slightly protruding fromthe
outer. Infrontalview, the aperture is situated atthe right ofthe middleoftheprevious
whorl andclearly turned upwards. Operculum corneous, witha distinctspiral ridge on
its outer surface
Dimensions: H2.4-2.7mm, B 2.2-2.4mm.
Derivationominis. — NamedaftermyfriendJens Hemmen,whofoundthisspecies.
Remarks.— Thisspecies livessympatrically with Opisthostoma (Plectostoma) christae. It
caneasily be distinguished however, sinceinA.jensithe apertureis turnedupwards, the
umbilicusis narrower, andthe peristome is flaring. Conchologically A.jensi differsfrom
A.panhaibythe lack ofaspiralstriation, the umbilicuswhichis noteccentric, thelower
numberofribs permm, andthe constrictionsituatedat0.5 whorlfromtheaperture.
ACKNOWLEDGEMENTS
Thanks are due to Prof. Dr. E. Gittenberger (Leiden) for critical reading the manu-
script, toJ.Goud(Leiden) whomadetheexcellentSEMphotographs, toR. Moolenbeek
(Amsterdam) for the loanofmaterialfrom ZMA, toDr. J.J. Vermeulen (Singapore) for
manyusefuldiscussions, andespecially to Christa andJens Hemmen(Wiesbaden) for
theirpermission to describematerialfrom theircollection.
REFERENCES
BENTHEM JUTTING, W.S.S., VAN, 1952. The Malayan species of Opisthostoma (Gastropoda,
Prosobranchia,Cyclophoridae),with acatalogueofall species hitherto described. — Bulletin ofthe
Raffles Museum24: 5-62.
, 1961.Additional newspeciesandnewlocalities ofthefamilyVertiginidaeandthegeneraOophanaand
OpisthostomafromMalaya.— Bulletin ofthe RafflesMuseum 26:34-48.
GITTENBERGER, E.,1995.On the onehand .... — Nature 373: 19.
KOBELT, W., 1902. Cyclophoridae.In: DasTierreich 16,Mollusca: 1-663.Berlin.
VERMEULEN, J.J., 1996. Notes onthenon-marinemolluscs oftheisland ofBorneo 8.The genusArinia;
additionstothe generaDiplommatinaand Opisthostoma(GastropodaProsobranchia: Diplommatinidae.
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