Table Of ContentElyt,・a,「okvo,30(1):207-213,June30,2002
LatePlioceneDonaciinae(Coleoptera,Chrysomelidae) fromtheKoka
Formation,KobiwakoGroupinShigaPrefecture,Japan
MasakazuHAYASHI
767-45-101,0hara,Sanda,Hyogo,669-1515Japan
and
Shigehik0SHIYAKE
OsakaMuseumofNaturalHistory,
NagaiPark1-23,Higashi-sumiyoshi-ku,Osaka,546-0034Japan
Abstract Threespeciesofthedonaciine fossilswereobtained from the Late
PlioceneKokaFormationontheriverbedoftheYasuRiver, Kosei-cho,ShigaPrefecture,
Japan.Thedonaciine fossilsareidentifiedwithPlateuma,・Isakiensls, Plateuma''Iscon-
st・,lctico11isandDonacia(Donac1ominla)sp.Thefossilageisca2.6Ma.
Thispaperdealswith thedonaciine fossils fromtheKobiwakoGroupinShiga
Prefecture,Japan.TheKobiwakoGroupisaninland freshwaterdepositthat isoneof
therepresentativestrataofthePlie-PleistoceneinJapan.Thoughmanyoftheforma-
tionsofthegroupincludelignitebeds, fossilinsectsfromthegrouphavepoorlybeen
known:ToMINAGAandInsectFossilResearchGroup(1993)hasbeentheonlyonere-
portingfossilinsectsfromtheKobiwakoGroup,including“Plateumarisakiensis?”on
theriverbedoftheEchiRiverinEigenji-cho,ShigaPrefecture.Thispaper isthesec-
ondreporton fossilinsectsfromthegroup.SinceseverallignitebedsoftheJapanese
Plie-Pleistocenestratayieldsabundant fossilbeetles,suchastheUonumaFormation
inNiigataProf.andKazusaGroup inSaitamaPref.,weanticipateabundant fossils
fromthegroupinthefuture.
GeologicalSetting
KAwABE(1989,1990and1994)reviewedthestratigraphyoftheKobiwakoGroup
andsubdivided it intoeight formations: Ueno, Iga,Aoyama,Koka,Game, Kusatsu,
KatataandTakashima,asintheascendingorder(Fig.1).Accordingtohispaper,the
geologicalageofthegroupcorrespondstotheLatePliocenetoMiddlePleistocene,
andtheaccumulationagewasestimatedat4.0to0.5Ma(SATOGUCHIeta1.,1999).
Thefossil localityistheriverbedoftheYasuRiver,Yoshinaga,Kosei-cho,Shiga
208 MasakazuHAYAsHIandShigehikoSHIYAKE
ll
、i,
5, 1;
:-:、 ・
,e
ol ll'
0.S
l・0
l・S
2.0
2.S
Ko可i
3.0
3.S
Fig. 1. Lithe-, magneto-,and tephro-stratigraphy of the Kobi-
wakoGroup(modifiedfromSAToGUcHleta1.,1999).
4.0
Prefecture,Japan(34°59'33″N,136°6'13″E:Fig.2).Inthisarea,theKokaFormation
isdistributedalongtheYasuRiver(ResearchGroup for theFossilFootprintsat the
RiverYasu,1998).The formationmainlycontainsgravel,sandandsilt butalso in-
terbeddedvolcanicashandlignitebeds.Thestratigraphicalpositionofthelignitebed
whichyieldsthedonaciinefossilsisby9mabovetheKosajivolcanicashbea,theage
ofwhich isestimatedca 2.6Ma(ResearchGroupfortheFossilFootprintsattheRiver
Yasu,1998).
LatePlioceneDonaciinaefromtheKobiwakoGroup 209
Fig. 2. MapshowingthefossillocalityintheYasuRiver.Usingthetopographicmaps“Mikumo”,scale
l:25,000bytheGeographicalSurveyInstitute,Japan.
Methodsand Materials
Thelignitebedsofthe formationarecompressedandcementedpeaty deposits.
All fossilspecimenswerefoundbysplittingthemalongthebeddingplanesandexam-
iningtheresultingsurfaces,andwerepreservedinshutcases inwetconditionwith
ethylalcohol.Mostspecimenswereexaminedunderastereoscopicmicroscope(SM)
andphotographswerealsotakenby usingSM.All fossilspecimensreported inthis
paperaredepositedintheOsakaMuseumofNaturalHistory(0MNH).Forcompari-
son,recentspecimensfrombothinOMNHandintheauthor'scollectionwereused.
DescriptionofFossils
Subfamily Donaciinae KIRBY
GenusPlateumarisTHOMSON
PlateumarlsakiensisToMINAGAet KATsURA
(Figs3A,B,C)
PlateumarisakienslsToMINAGAetKATsURA,1984,Bu11.0sakaMusnat.Hist.,(37):25.
Description. Colorationofpronotum,elytronandsternaofabdominalsegment
entirelymetallicgreen.Pronotummoreorlessquadrate;discdenselypunctate;median
lineindistinct,sometimesdistinct;basalsulcuspresentbutshallow,puncturescoarse
andsparse;callosalsulcusindistinct;anterolateralcalluspresent.Elytra1discwithten
completepunctatestriaeandascutellarstriole;interstriaeshiny; interstria1rugaeen-
tirelydistribute radiating fromstria1punctures,becoming finer anddenserapically;
210 MasakazuHAYASHIandShigehikoSHIYAKE
sutural intervalnarrowedsubapically,innerandouterbeadsconvergent,andexplanate
suturalmarginexposing;apexrounded.
Measurements. Pronotum: length,1.4-1.5mm(n=3).Elytron: length,4.2mm;
width,1.5mm(n=1).
Remarks. Thisspeciescanberecognizedbydensepuncturesonpronotaldisc
(Fig 4A).ThepronotumofPconstrictico11ismaybesimilartothatofRakiensls,but
LatePlioceneDonaciinaefromtheKobiwakoGroup 211
Fig.4. PronotumofrecentPlateunla・,Isspp:A, aklensls;B,i:)const,-1cticoliis. Scalebar=1.0mm
thediscoftheformerissmootherthanthatofthelatter(Fig.5B).Recent akiensis is
avery rarespecies inJapan;thepresentpopulationsarelimitedtoGeihoku-cho,Hi-
roshimaPrefecture(ToMINAGAeta1.,1984).The fossilof thisspecieswasoncere-
ported fromtheLateMiocenetoPlioceneHogiLigniteFormationinKetaka-cho,Tot-
tori Prefecture (Fossil Insect Research Group for Nojiri-ko Excavation & AKAGI,
1986).ItsdiscoveryfromtheKokaFormationindicatethatRakiensiswasdistributed
inKinkiregionintheLatePliocene.
afeMlariscons加'ctl'coals(JACOBY)
(Fig3D)
Donaclaconst1-1ctico//tsJACOBY,1885,Proc.zool.Soc.Lend.,1885:192.
Plateltma''tsconst1'tctlco11is:JACOBSON,l892,HoraeSoc.ent ross.,26:434.
Des_ription. Pronotummetallicpurple.PronotaI outlinemoreor less cordate;
anterolateral calli prominent, callosal sulci present with rugae; disc entirely shiny,
punctulatedandrugoseinanteriorhalf;basalsulcuspresent,withscatteredrugaeand
punctures;medianlinecontinuous.
Measurements. Pronotum:length,1.5mm(n=1).
Remarks. FossilrecordofthisspeciesisrareinwesternJapan thoughreported
fromtheLateMiocenetoPlioceneHogiLigniteFormationinKetaka-cho,TottoriPre-
fecture(FossilInsectResearchGroupforNojiri-koExcavation&AKAGI,1986).
Donacia(Donacio″lima)sp.
(Fig5)
Description. Coloration of elytron metallic green. Elytron subpara11e1-sided
from basetomiddle, gradually narrowed toward apex, with ten complete punctate
212 MasakazuHAYAsHlandShigehikoSHIYAKE
Fig.5. Le量elytronofDonacia(Donaciomima)sp. Scale
bar=1.0mm.
striae;stria1puncturesnearlyverticaloval;all intervalsshiny,rugu1ose,punctulate;su-
tural interval graduallynarrowing to apex; other intervalswith transverserugaebe-
tweenthem;apextruncate,outerandinnerapicalanglesnearlyright.
Measurements. Elytron:length,5.8mm十;width,1.9mm(n=1).
Remarks. Elytra1rugosityissimilartothatofDonaciaclavareauiJACOBSONand
relatedspecies.
要 約
林 成多・初宿成彦:古琵琶湖層群甲賀累層から産出したネクイハムシ亜科(甲虫目ハムシ
科)の化石. - これまで古発琶湖層群からの昆虫化石の記録は, わずか1例のみであった.
筆者らは滋賀県甲西町の野洲川に分布する甲賀累層を調査した結果, 亜炭層からネクイハムシ
亜科の化石を得ることができた. 小佐治火山灰 (約260万年前) に対比されている火山灰層の
上位から, 3種のネクイハムシ亜科甲虫が産出し, アキミズクサハムシPlateumarisakiensis
ToMINAGAetKATsURA,オオミズクサハムシPlateumarisconstrictico/1is(JACOBY),フトネクイハムシ
LatePlioceneDonaciinaefromtheKobiwakoGroup 213
亜属の1種Donacia(Donaciomima)sp.と同定された. アキミズクサハムシは現在, 広島県芸北
町のみから知られているが, 本化石記録は本種の後期鮮新世の分布を考察するうえで重要な発
見である. 古琵琶湖層群には多くの亜炭層が挟まれており, 今後の調査で新たな化石の発見が
期待される.
References
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Elytra, 「okyo,30(l):213-214,June30,2002
NewRecordofE1odesburmensls(Coleoptera,Scirtidae)
from Vietnamand India
HiroyukiYosHIToMI
BioindicatorCo.,Ltd.,(Sapporobranch),
Kita1,Nishi2-11,Chuo-ku,Sapporo-shi,060-0001Japan
E1odesburmensis KLAUsNITzERwasoriginallydescribed from MyaMnar, and has been
