Identification and Some Morphological Characters of Clethrionomys rufocanus and Eothenomys regulus from USSR, Northeast China, and Korea in Comparison with C. rufocanus from Finland-香川大学学術情報リポジトリ

IdentificationandSomeMorphologicalCharactersof

（’／（イ／／／●／り刷りノ左It、ヾJ・／（／；ノ川ノ＝バこ111（1どり／／／し〃りノ叩ヾハ．ヤー／／／／／J

fromUSSR，NortheastChina，andKorea

inComparisonwith C．ク頑canusfromFinland

YukibumiKANEKO β／（）ん甘ん、（7／⊥‘7／−（明7J明・．J−17（、J／坤・〃■∫（山（・（汀正明，〃‘ぜ1：け‘7し7JJ／J、り叫l・． 花々α桝αね〟間ノ（砂α乃 （AcceptedSeptember25，1989） AbstYaCi．Museumspecimensof210redLbackedvolesfromUSSR，nOrtheastChina （Manchuria），and Korea were compared with 70 specimens of Clethriono叩 ndbcanusfromFinland．Condylobasallength（CBL）correlatedpositivelywithages determined by developmental stages of molar roots in the samples from Finland

throughouttheyear．AllskullsmeasuringCBL＝26mmormorehadrootsinthe SamplescollectedfromFinlandinthefirsthalfoftheyear．IntheAsiaticspecimens CO11ectedinthefirsthalfofayearandfrom4lONlatitudeandnorth（northernvoles）， allskullswith26mmCBLormorelackedalveolarcapsules，indicatingthedevelop− mentofroots．Onthe！Otherhand，inmuseumspecimenscollectedinthefirsthalfof theyearandfrom410Nlatitudeandsouth（southernvoles），allskulls，eVeninskulls with26mmCBLormore，hadstronglybulgedalveolarcapsules，indicatingrootless molars．TheocclusalpatternsofM3changewithincreaseinCBLwerethesame betweenC．ndbcanusfromFinland品dnorthernvoles：Simplexformwascommon inlargerindividuals，Whereasthecomplexformwasrare．Ontheotherhand，the COmplexformwasabundantinallCBLclassesinsouthernvoles．Northernvoles WereSlightlynarrowerininterorbitalwidthandslightlyshorterintaillengththan SOuthernones．IidentifiedthenorthernvoleasC ndbcanus，andthesouthernvole as Eotheno叩 御Ius．Isuggest that the true geographicaldemarcationline

betweenthetwo specieslies on thewestern andsouthernboundary ofthe Kaima

Plateau，NorthKorea．

Key wo7ds：ClethriononvLS ndbcanus；Eotheno叩 Y℃guhLS；Identification；Distri−

bution；EasternAsia．

Introduction

Withtheexceptionof ClethYionoクク砂S ndilus，the classification of red− backedvoles（ClethrionoククりSandEothenonws）fromnortheastChina（Manchur− ia）andKoreahasbeenveryconfused．Thered−backedvoleofKoreawasfirst describedby Thomas（1907）under the name of Cmseoクク砂S regulus．Allen＆ Andrews（1913）andSowerby（1923）identifiedthevolefromKoreaandnorth− eastChinaas CγαSeOmyS rqgulus．In1926，Hintonrevisedtheclassificationof

red−backedvolesfromeasternAsiaandrecognizedonlyonespeciesofvolein

this region，namely EuotoブタひS（＝Clethriononv）S）n4fbcanus．Since that time， manytaxonomistshavefollowedhisclassificationatthespecieslevel（Howell，

1−．Ⅳ（川ヒ、片〔） 130 1929；Goodwin，1933；Kuroda，1934，1938，1939，1940；Allen，1940；Tokuda， 1941；Ellerman，1941；Mori，1942；Ellerman＆Morrison−Scott，1951；Ognev， 1950；Jones＆Johnson，1956，1965；Shou，1962；Won，1961，1965；Gromov et al．，1963；Zimmermann，1964；Gromov ＆ Polyakov，1977；Aimi，1980； Gromov＆Baranova，1981）． Corbet（1978），however，prOpOSedanewclassificationofOrientalvolesof thisreglOn．HeallocatedthevolefromKoreaandtheProvincesofShansiand

Hopei，China，tO Eothenoプ呵′S，but also recognized C．n4bcanusin northeast ChinaandKorea．Honackiet al．（1982）followedtheclassificationofCorbet （1978）as did Nadachowski（1984）．However，the descrimination of C． n4bcanus and E．r曙ulus remains unsettled，because Corbet（1978）only pro−

Videdsomesimplekeysforthesegroupsandacrudedistributionmap．

Inthepresentpaper，Icomparecranialandmolarcharactersofred−backed VOlesfromUSSR，nOrtheastChina，andKoreawiththoseofC．radbcanusfrom Finland．Bythesecomparisons and examination ofagevariation，Ipresent morepracticalcriteria foridentifying ClethrionoクワりS ndbcanusinthisregion

SeparatingitfromEothenonws rqgulus．

Materials and Methods

A totalof280specimens was examined：70specimens of C．n4fbcanus collectedfromKilpisjarvi（69003′N，20049′E），FinlandfromFebruarytoSeptem− ber，1983，byA．Kaikusalo；and210specimensofClethrionon砂SandEotheno− nりSfromUSSR，nOrtheastChina，andKoreahousedinthefollowinginstitu− tions：BritishMuseum（NaturalHistory）（BM），UK；MuseumofComparative Zoology，Harvard University（MCZ），American Museum of NaturalHistory （AMNH），UnitedStatesNationalMuseumofNaturalHistory（USNM），and FieldMuseumofNaturalHistory（FMNH），USA；andYamashinaInstitutefor Ornithology（YIO），Chiba，Japan・

Thelocality anditsreferencenumberinFig・9，1atitude，longitude，date collected，muSeum，and registration number of allspecimens examined are listedinthe Appendix．Latitude andlongitude ofthelocalities were deter− mined from the gazetteersinJohn＆Johnson（1965），Zhuang（1983）and Su （1984）．Someofthesespecimenswerepreviouslydescribedandidentifiedby Thomas（1907），Allen＆Andrews（1913），Sowerby（1923），Hinton（1926），Howell （1929），Goodwin（1933），Kuroda（1934，1939），Allen（1940），Jones＆Johnson（1956， 1965），Corbet（1978），andAimi（1980）． Taillength（TL）wasrecordedfromtheskinlabeL Condylobasallength （CBL）andinterorbitalwidth（IOW）weremeasuredonundamagedskullstothe nearest O．1mm with a dialcaliperby the author．The CBLis the distance betweentheoccipitalcondyleandtheanteriorpartofpremaxillae・TheIOW

istheleastdistanceofthefrontalbonesbetweenorbits．

ThedisappearanceoftheM2alveolarcapsulewasrecordedfortheskulls

Koshkina，1955）．Three stages were recognized：a StrOng arChed alveolar CapSule；anintermediate stage，in which the capsuleis slightly swollen；a Cap？uleflattenedandreducedtoastraightline・ SkullsofC．クゆcanusfromFinlandwereagedaccordingtothedevelop− mentalstagesoftheirmolarrootsfollowingthecriteriaofAbe（1976）．Eight ageclassesweredetermined：Ⅰ＋II，ⅠII＋IV，Ⅴ，lessthan33％ofrootratio（VI）， from33to60％ofrootratio（VII），and61％ormoreofrootratio（VIII）． PatternsofcrownwearofM墨weredrawnforC．ク頑canusfromFinland by the stereo microscope（SMZ−10）produced by Nippon Kogaku with an accessory apparatus at15Ⅹmagnification．For museum specimens，figures Were drawnfrom close−up Pictures ofthe molar rows（1．75Ⅹmagnification） usingthestereomicroscopeat6．6Ⅹmagnificationafterthepicturesweretaken inthemuseumwithanaccessoryclose−uplensattachedtoanOlympuscamera． DentalpatternsofM旦wereclassifiedintofourtypes（Abe，1982）：type4＋5is

COmplexformwiththreereentrantanglesonthebuccalside；type6hasthree

Salientanglesonthebuccalside，aShortposteriorloop，andaconfluentdental isthmusbetweentriangles；type9hasthreesalientangles，inwhichtheinternal

posterior enamellamella arestraightto convex；type7＋8has three salient

angles on the buccalside with slightly concaveinternalposteriorlamella

exceptfortype9．Furthermore，thefourthoutersalientanglewascheckedon

theleft side of M3．

Results

l．1hriation qfClethrionomysrufocanusjhm j巧nland

InthelargesampleofC ndbcanusfromFinland，CBLcorrelatespositive− 1ywithsixageclassesdefinedonrootdevelopment（r＝0．790，U＝67，P＜0． 001）andmaybeusedasanapproximateindicatorofage（Fig．1）．Twoskulls havinganintermediatestageofthealveolarcapsule，OrWithoutthecapsule， arefoundamong15specimens（13％）inthe22−24mmCBLrange（Fig．1）．Ten

Of18specimen岳（56％）with25mmCBLlackacapsule・Allskull占measuring

CBL＝26mmormoreexhibitrootdevelopmentandthealveolarcapsulehas disappeared（ⅤⅠ，ⅤⅠIandVIIIageclasses）．

ThedisappearanceofthealveolarcapsuleinrelationtoCBLwascompar−

edamongthesamplescollectedindifferentmonths（Fig．2）．In C．glanolus，

thedevelopmentofmolarrootsisknowntoberetardedintheautumn−born

cohort compared with spring−Or Summer−born cohorts（Lowe，1971；Zejda，

1971）．AmongspecimenscollectedinFebruary，March，andMay，thecapsule disappearedin animals as smallas CBL＝24mm；Whereas，amOng those

takeninJulyandSeptember，thecapsulewasabsentonlyinindividualswith26

mmCBLormore（Fig．2）．SpecimenscollectedinthelatermonthswithCBL

lessthan26mmpossessanalveolarcapsule，Whichsuggestsaretardationof

molar formation．In the followlng COmparison of capsule development，

museumspecimensweredividedintotwo periodsaccordingto thecollecting

132 l二ん7机丸） ・‥I・Itトヰー ● ●● ■hl●l●− ● ⅦⅠ Ⅶ VI V III＆Ⅳ Ⅰ＆Ⅰ ム ● ● A 。。○く辟。80 ● 0 00 08 22 23 24 25 26 27 28 29mm CBL

Fig・1・Relationship between condylobasallength（CBL），age Classes（I−VIII）and

development ofalveolarcapsulein C．ndbcanus from Finland．SymboIs：CapSule present＝Open Circle；CapSule absent＝Closed circle；andintermediate stage＝ OPentriangle．

Fig・2・Monthlyvariationoffrequencydistributions ofcondylobasa11ength（CBL） With development of alveolar capsuleinC．rt4bcanus from Finland．One square indicates one specimen．SymboIs：CapSule present＝Open reCtangle；CapSule absent＝Smallclosedrhombuswithinasquare；andintermediate stage＝Ⅹ−1etter withinasquare．

Tablel・FrequenciesofdentalpatternsofM30nbothsidesinClethriononv7S

ndbcanusfromFinland．

Left side

Type6 Type4＋5 Type7＋8

T _{p y e} 9

Rightside Type6 Type4＋5 Type7＋8 Type9 Total 0 6 5 0 1 1 0 3 7 9 9 2 3 0 0 3 1 4 1 1 6 9 5 0 0 3 2 7

Table2．Frequencies of dentalpatterns of theleft M3in Clethrio

ndbcanusfromFinlandobservedinsevenCBLclasses．

CBLclasses（mm） Type6 Type4＋5 Type7＋8 y T p e 9 22．0−22，9 23．0−23．9 24．0−24．9 25．0−25．9 26．0−26．9 27．0−27．9 28．0−28．9 Total 0 0 0 2 6 2 0 0 1 O 1 8 0 2 7 1 9 1 1 3 0 0 0 6 6 2 0 4 1 1 6 8 8 4 1 1 9 1 2 1 6 （JulytoDecember）．

Thecorrespondence ofthe occlusalpatterns betweentheleft andright

M旦s was tested（Tablel）．The G−teSt With Williams adjustment（Sokal＆

Rohlf，1973）indicatedthatbilateralpatternswerestronglyassociated（Gd5＝ 56．3616，U＝9，P＜0．005）．0nly theleft side pattern was examinedin the

followlngStudy．

ThedentalpatternofM旦ChangeswithincreaseinCBL（Table2）．Type 6wasthemostfrequentintheCBLclassesunder24mm．（Thesimplexform （type7＋8）variedgreatlyfrom17tolOO％in23−27mmCBLclasses．Another Simplex form（type9）occurred at O−33％1evelin23−27mm CBL classes．

Thecomplexform（type4＋5）wasobservedatll−25％1evelin25−27mmCBL

Classes．Thus，the two simplex forms（type7＋8and tiTpe9）were foundin largenumbers（75−100％）in24mmCBLclassormore．

AfourthoutersalientangleofthegrindingsurfaceinM3wasobservedin

Onlyoneskullamongthe70specimensof C．ndbcanusfromFinland．

TheIOWandTLofC．n4bcanusfromFinlandvariedseasonally（Fig．3）：

IOWorTLareslightlynarrowerorshorterinFebruai・ythan’inothermonths

and are slightly wider orlongerinJune thanin other months．TheIOW

134 ト 〟（川亡・ノh

陀B5一箪r

MAR l t．−

￣−1−

m

鮭虹止且臥軋⋮TL

●：ニー≡

P 1虹

Fig．3．Monthly variation of frequency distributions ofinterorbitalwidth（IOW） andtaillength（TL）inrelationtodevelop・

ment of alveolar capsulein C．n4bcanus

from Finland．，One rectangle shows one SPeCimen．SymboIs：CapSule present＝ open rectangle；CapSule absent＝Closed rectangle；andintermediatestage＝Ⅹ− 1etterwithinarectangle． 」UL SE ●∴11J・右／∴・ノト：′−、／・しt、／ルノノバ・・・イ／‥ん／ノ）．り′一／−．＼ヾ人′、，．．一〃／／‥／ヾ／〔Ⅵ／ノ＝．．′ノ．・．／八．り1．′

PlotsofCBLandtheoccurrenceofthealveolarcapsulewerearranged

fromnorthtosouthanddividedintotwoperiods（fromJanuarytoJune，and fromJulytoDecember）forthemuseumspecimensexamined（Fig．4）．Inthe

firsthalfoftheyear，thealveolarcapsuleis absentin allskullsmeasuring

CBL＝26mm or more（andin some skulls only24and25mm）from410N

latitude and north；Whereas，from4lONlatitude and south，the capsuleis uniformlypresenteveninskullswith26mmCBLormore．Alternatively，in

thesamplesofthesecondhalfoftheyear，thecapsuleisabsentintwoskulls

（locality9）measuringCBL＝25−26mmfrom4lONlatitudeandnorth，andthe CapSuleispresenteveninskullswith26mmCBLormorefrom410Nlatitude and south ThefrequencyofM旦dentalpatterns（Fig．5）indicatesthatsimplexforms

（type7＋8and type9）（Fig．6）are most common（91／109＝83．5％），and the complexform（type4＋5）（6／109＝5．5％）andthefourthoutersalientangle（4／

109＝3．5％）are uncommon among northern voles．In contrast，the simplex

formisuncommonamongsouthernvoles（23／97＝23．7％），thecomplexformis themostdominant（69／97＝71・1％）・andthefourthangle（Fig・6）ocurred

frequently（59／97＝60．8％）．However，geOgraphicalclinalvariationlS nOt

N 12 34 「 5 6 R 4g ₈₇ m 9 ≡ LU ⊂】 ＝） 10 ト ［ く m ₁₂ 13 1‘ 4d- 」＿］ ［［ 3334 3弓 ［ 20 24 28 20 2ム 28mm CBL CBL −A− −B− Fig・4・Latitudinalvariationoffrequecydistributionsofcondylobasallength（CBL）

withdevelopment ofalveolar capsuleln Samples ofred−backed voles from USSR， northeast China，and Korea．The numbers（1−34）show thelocalities which are explainedinthe Appendix．Theleft column（A）contains samples collected from JanuarytoJuneandtherightcolumn（B）samplescollectedfromJulytoDecember． FurtherexplanationisgiveninFig．3．

】￣、八一〃し丸） 136

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35L止

叫 ん L＿血＿…□ ロー7 JUL 賦 t rr￣「！…．−．18 l！rr ‥…．−一19

止L＿＿．．□20

しrTr＝．．．一口21 三三 t rTr．．…［コ24 トrl＝ト＿＿⊂コ25 ■ ＝ ［！．…トー26

址‖．＿］28

＝「＝巨．□29 8I！．「「．．．■＿

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JUN JUL

岨

10 し≡，rr叫＿ □ 30

‖」山

一25L』

岨｛［31

＝「「‥＿．．□32 ！「「1＿．上］33 ■ rr こ ‥．．．．⊂コ34 ，．．□

13」L□．．＿．−

1‘L』＿＿．⊂コ

151r￣「！．…⊂コ 16ロ＿」コー．…□ 豊野Ld lu虔﹂巾S壬寸 の山d＞ト の◆ト山d＞ト 爪◆寸山d＞卜 り山d＞ト む−ひ⊂d l⊂巾旧市S占ヾ の山d＞ト の．ト山d＞ト 山◆寸山d＞ト ∽山d＞卜 Fig．5．Frequencydistributionsofdentalpatterns（type6，type4＋5，type7＋8，and type9）andtheoccurrenceofthefourthoutersmallsalientangleintheupperleftside

M3insamples ofred−backedvolesfrom USSR，nOrtheastChina，andKorea．The nt品bers（1−34）showthelocalitieswhichareexplainedintheAppendix．

．」 β （、

Fig．6．Common dentalpattern of M3．

A，the simplex form of northern vole

（AMNH34038collected fromlocalityll，

COndylobasallength＝25．4mm with roots）；B，the complex form of southern

VOle（USNM199665collectedfromlocality

14，COndylobasallength＝25．3mmwithout roots）；C，the complex form with the fourthoutersma11salientangle（arrow）of

southern vole（USNM 294646 collected

fromlocality20，COndylobasallength＝25． 2mm without roots）．Thelocality num− bersareshownintheAppendix．

繁治責闇U

l■■

ThefrequencyoftheM3dentalpatternsinrelationtoCBLisshownforthe

samplesfromlocalitiesl，5，7and9（Table3），and27and30（Table4）．Other samplesaretoosma11innumbertotabulate．Inlocalitiesl，5，7and9，the simplexforms（type7＋8andtype9）occurprincipallyinanimalswithlarge CBL，thecomplexform（type4十5）isinfrequent，andtype6wasobservedin animalswithasmallCBLexceptforlocality5，Wheresmall−Sizedindividuals are absent．In contrast，mOSt Skulls fromlocalities27and30possess the complexformatalmostallCBLsizes，andthesimplexformsareuncommon． Inthemuseumspecimens，theIOWrangedfrom3．2to4．1mmforspecimens collectednorthof4lONlatitude；Whereasthewidthvariedfrom3．9to4．7mm forspecimensfromsouthof410Nlatitude（Fig．7）．TLrangedfrom20to49 mminnorthernvoles，andfrom30to54mminsouthernones（Fig．8）．Thus，

northernvolesareslightlynarrowerininterorbitalwidth andshorterintail

than southernindividuals． 3．7bo乃0ク鶴首c c（フ乃CJ〟ざわ乃

Therewasasharpcontrastinmolarrootoccurrencebetweennorthern？nd

southernvolesamongthespecimenscollectedinthefirsthalfofayear（Fig．4）・ Thenorthernvolehasrootedmolars，WhichbegintodevelopfromCBL＝24to 25mm．Furthermore，amOngnOrthernvoles，thesimplexformofthedental patternisthemorecommon，thecomplexformisuncommon，thefourthouter salientangle occurredin a smallnumber（Fig．5），andtype6withconfluent dentalisthmusappearedinthesmalトsizedCBL（Table3）．Thesecharacteris− ticsarethesameasdescribedforC．ndbcanusfromFinland（Fig．1andTable 2）．Consequently，Iidentifythevolescollectedfrom410NandnorthasCleth− ル・頼りり・．＼Ⅵ／こぃ／′′〃＼．

The voles collected from410N and south are allocated to Eothenon砂S regulus．This species has the same palatalshelfin the skullasin Cleth−

Yionoqsbutlacksrootsevenin oldage，andthemolarreentrantfolds are

138 1￣、〃（7〃（、毎

Table3．Frequencies ofdentalpatterns oftheleft M3inred−backed voles from USSR and northeastChina foundin CBLclasses．

CBLclasses（mm） Type6 Type4＋5 Type7＋8 V− T p e 9

Locality1 23．0−23．9 24．0岬24．9 25．0−25．9 Total 1 5 6 2 1 Locality5 24．0叫24．9 25．0−25．9 26．0−26．9 Total 8 2 1 1 1 Loca王ity7 22．0−22．9 23．0−23．9 24．0−24．9 25．On25．9 26．0−26．9 Total 5 1 1 3 1 1 1 Locality9 20．0−20．9 21．0−21．9 22．0■22．9 23．0−23．9 24．0−24．9 25．0−25．9 26．0叫26．9 Total 0 0 0 0 1 1 0 2 2 0 2 3 4 2 1 4 1 tionoftraitsformsthegenericdiagnosticofEothenoクワ砂S（Hinton，1926；Eller− man，1940；Corbet，1978）．BecausetheholotypeofCYtlSeOプ呵ノSrqulusThomas， 1907（BM6．12．6．89）isfromlocality30（Figs．4，5，7，and8，andTable4），the SOuthernvolecanberecognizedasE．rqulus．Eotheno〝りLS Yqulus averages

Slightly widerinIOW andlongerin TL than C．ndbcanus from the USSR， northeast China，and North Korea；however，IOW and TL show slight se良一 SOnalvariationin C．ndbcanusfromFinland（Fig．3），andtherangesofIOW andTLoverlapbetweenthetwospecies（Figs．7and8）．ThedistributionofC． radbcanusandEク聯Iusisshownbythelocalitiesexaminedinthisstudy（Fig． 9）． Discussioll FewstudieshavebeenmadeonthedevelopmentofmolarrootsoronM3 0CClusalpatternchange with CBL growthinthenominatesubspecies of C．

山口⊃トl↑く﹂ 3．2 4．0 4月 32 48 ‘8爪m IOW IOW −A− −B一 Fig・7・Latitudinalvariationoffreque？Cydistributionsofinterorbitalwidth（IOW）

withdevelopmentofalveolarcapsulelnSamplesofredLbackedvolesfromUSSR，

northeastChina，andKorea．FurtherexplanationisgiveninFigs・3and4・

1二 八’（丁招来） 140 山D⊃ト︻↑＜﹂ 15 35 55 15 35 55mm TL TL −A− −B−

Fig．8．Latitudinalvariation of frequency distributions of tai11ength（TL）with developmentofalveolarcapsuleinsamplesofred−backedvolesfromUSSR，nOrtheast

Table4．Frequencies of dentalpatterns oftheleft M3in red−backed voles

fromKorea foundinCBLclasses．

CBLclasses（mm）

Type6 Type4＋5 Type7＋8

y T p e 9

Locality27 21．0−21．9 22．0−22．9 23．0−23．9 24．0−24．9 25．0【25．9 26．0−26．9 Total 1 0 3 4 3 3 4 1 0 0 0 2 0 2 4 2 1 3 6 3 5 0 2 Locality30 21．0−21．9 22．0−22．9 23．0−23．9 24．0【24．9 25．0−25．9 26．0−26．9 Total e 13222yp13 T 3 ＊ 1 3 3 2 3 3 5 1

＊Theholotypeof CYaSeOnV｝S喝ulus Thomas，1907（BM6．12．6．89）isclassifiedinthis

CategOry． thecementspacesofmolarsareclosingatapicalportionsofroots，thegrowth StageOfwhichcorrespondswithmyfindingthatskullswith24−25mmCBL exhibittheinitialstageofroot−Closing（agegroupIII＆IV）（Fig．1）．Further− more，hei11ustratedmolarswithrootsforspecimenswithCBL＝26．1mmor more・Thus，hisfragmentarydescriptiondoesnotcontradictmyresults． Miller（1912）andCrowcroft＆Godfrey（1959）studiedtheoccurrenceofa COmplexM旦in C・n4bcanusfromScandinavia，buttheydidnotpresentage

Variation and theirlocalities examined．In theisland population of C

nihcanus onHokkaido，Japan，Abe（1982）demonstratedthatthetype6was dominantinyounganimalsandthendecreased，thatthecomplexformoccurred lessthanlO％tillagegroupV，andthatthesimplexforms（type7十8andtype 9）increasedinnumberwithage．Thus，hisfindingsaccordwithmystudyof C・n4bcanusfromFinland．Dentalpatternsmayvarygeographically，because theproportionofthecomplexformis6．2％（1／16）inScandinavia（Miller，1912）， 14・5％（10／69）inFinland（Table2），9％inHokkaido（Abe，1982），andO−9．1％in localitiesl，5，7，and9，nOrtheastChina（Table3）．

Skulls and dentalcharacters of C．n4bcanus from northeast China and

Koreahavenotbeenstudiedindetail．Hinton（1926）examinedspecimensfrom

LakeBaikal，Irkutsk，USSR，andKorea，butdidnotexaminespecimensfrom northeastChina・Hestudied four specimens with roots fromIrkutsk，three

SpeCimenswithrootsfromPotaidonandPochong，NorthKorea，and12speci− mens without roots from South Korea．Based on these examinations，he allocated the voles from northeast Chinaand Korea to Euotonqys（＝Cleth− rionoク叩S）ク頑canusク聯Ius，becauseheconsideredtherootdevelopmenttobe

142 _{1−．〃‘J〃t・Å・り}

11ざ 12ざ 12ざ 13〔F 13ごE

Fig・9．Localities of C．n4bcanus（a closed circle）andE．rqulus（an open circle） identifiedinthepresentstudy．Thenumbers（1−34）indicatethelocalitieswhichare

explainedintheAppendix．

retardedinparallelamongthenortheastChinaandKoreanvole（C．n4bcanus regulus），theChinesevole（C．n4bcanus shanseius）andtheJapanesevole（C・ r84bcanus smithii）．However，myStudyshowsthat，aSfoundin C．n4bcanus

from Finland，Skulls with26mm CBL or more have rootsin allmuseum

specimens collected at or north of4lON andin the first half of a year・ Consequently，thedevelopmentofrootsdoesnotabatein C．プ頑canus from eastern Asia as stated by Hinton（1926）；Only the samples collectedin the

secondhalfoftheyearfromFinlandandeasternAsiashowretardationofroot

development（Figs．2and4）．Ontheotherhand，VOleslivingsouthof410Nlack roots，eVenin those with26mm CBL or more．With regard to rooted or rootlessmolars，aSharpcontrastexistsnorthandsouthof41DN．Thepresent findings，therefore，CannOtSuppOrttheclassificationofHinton（1926）．

Howell（1926）（theYaluRiver，NorthKorea），Kuroda（1934）（SouthKorea）， Jo′neS＆Johnson（1965）（theYaluRiver andSouthKorea），Won（1961，1965） （South Korea）and Aimi（1980）（South Korea），tOO，did not pay attention to

molarrootconditionintheclassificationofvoles．Iexaminedalltheirspeci− mens（exceptWon，1961，1965），andfoundrootlessmolars amorigthesespeci− mens（Fig．4）．Tokuda（1941）examinedred−backedvolesfromnortheastChina

and Northland South Korea，but did not distinguish skulls with orwithout

roots．Thus，hisdataonthedentalpatternfrequencyisnotcomparablewith

thepresentstudy．

Corbet（1978）distinguished C．n4bcanus andE．Y＜gulusinthisregionby

the character of rooted or rootless molars，Which accords with the present

taxonomicconclusion．However，hiskeyisnotalwayscompleteforpractical

identificationbecausehedidnotanalysethesizerangeofskullsthathaveroots

andthosethatdonot．AlthoughNadachowski（1984）distinguishedtwospecies from NorthKoreafollowingCorbet（1978），hedidnotspecify theskullsizes Withandwithoutroots．Fromthisstudy，thesetwovolescanbeidentifiedby

theabsenceorpresence ofrootsatleastin26mmCBLormore，Whenvoles

werecollectedduringJanuarytoJune．Furthermore，theinterorbitalwidthis

also a key character to discriminate the two speciesin this reglOn：Whenit exceeds4Amm，itisE Hinton（1926）mentionedthattheM旦OfyoungEvotoプクV）S ndbcanusク聯Ius （＝EothenoブタひS rqgulus）tendstobemorecomplex．However，hisobservation

isnotsupportedbecausethecomplexform（type4＋5）wasfoundinallCBL

Classes（Table4）．Thefourthoutersalientangleisacommoncharacter（Figs． 5and6）asdescribedinHinton（1926）andNadachowski（1984）．

Jones＆Johnson（1965）distinguished C．rtち舟canus Yqulus（＝E．regulus） from C．γゆcanus a7Seわevi（＝C．ndbcanus）from North Korea by a wider

interorbitalwidth，longertaillengthandothers，thoughtheymisidentifiedone SpeCimen（AMNH34011）of C．nttilus as C．n4舟canus a7uわevi．Theformer

two characterswereconfirmedinthisstudy．

Someauthorsnotedhabitatforred−backedvolescollectedinthisregion． However，becauseidentificationissometimesuncertain，Irefertothedescrip− tion of the voles thatIexaminedin this study．Allen＆Andrews（1913）

reportedthatthehabitatisthinlyorheavilyforestedintheTumenRivervalley

（localitylO）and the edge of primevalforestsin Nonsatong（localityll）． Sowerby（1923）collecteda1argenumberofred−backedvolesinforestedareas （ImienMpO，locality7）andintheopenvalleyofthelowerSungari（locality9）； thesespecimensareidentifiednowasC．ndbcanus． Thomas（1907）describedthehabitatoftheholotypeof CγαSeOnサSプ守宮ulus

as“mossytalusovergrownwithbushes”and“fromburrowinbarleyfieldon

dryhillside”fromthefieldnoteofM．P．Anderson．Hisoriginalfieldnotes further mentioned：“The vole653etc．（now registered as BM6．12．6．98）is

COmmOninthisneighborhood．Itchieflyaffectstherocksbutisalsofoundin

grassyembankments，Whereitburrows near the surface．Ihave sometimes

144 1’．ん〃汀如

“AtMingyong（＝locality30）isoneoftheKing’sreservedforests，Itconsists Ofscattered pines of fair size，and oh some of the higher slopes，firs．The

mountains are rocky and unfertile and the soil seems to retain moisture

poorly”．Ontheskinlabels，thehabitatisdescribedasfollows：“Mossystones amongbushes；Burrowinstone−Wa11edembankment；Byrockamongbushes and grass；Stone，Wallon grassy flat；Under decayinglog on hillside”・

Therefore，these habitat descriptions suggest that E．rqgulus prefers princi− pa11yrockyareas，Whereas C．クゆcanuslivesmainlyinwoodedareas．

In comparison with the map of Corbet（1978），the distribution of C．

ndbcanus extendsfartherto thewestinnortheastChina andlessto southin

NorthKorea（Fig．9）．Nadachowski（1984）reported C．ndbcanus from Sam−

jiyon（4lO29′N，128012′E），Hyesan（41014′N，128007′E）andPektu−San（42000′N，1280

03′E），andE．rqulus wascollectedfromSokvang−Sa（38035′N，127013′E）and Kumgang−San（38040′N，128008′E）．Therefore，Isuggest that the southern

distributionallimitofC．ndbcanusisthewesternandsouthernboundaryofthe

KaimaPlateau，NorthKorea，ahigh1andthatKishida＆Mori（1931）andJones ＆Johnson（1965）notedismostlycoveredwithconiferousforestsresemblingthe flora of northeast China．However，the northeast boundary of E．

needs to be clarified．Li（1983）collected C．ndbcanus from the Liaodong Peninsula，China，neartheYaluRiver，buthismethodofidentificationfor C．

n4bcanuswasnotgiven．

Acknowledgements

Igratefully acknowledge Mr．Asko Kaikusalo，Who provided me with

excellentspecimensfromFinland，andthecuratorswhoallowedmetoexamine

specimensin their care：Mr，Iain R．Bishop，British Museum（NaturalHis−

tory），Mrs．MariaE．Rutzmoser，MuseumofComparativeZoology，Harvard University，Dr．Guy G．Musser，American Museum of NaturalHistory，Dr・

MichaelD．Carleton，UnitedStatesNationalMuseumofNaturalHistory，Dr． BruceD．Patterson，FieldMuseumofNaturalHistory，andMr．K．Momose， Dr．R KakizawaandDr．N．Kuroda，YamashinaInstituteforOrnithology．I furtherthankDrs．M．D．CarletonandG．B．Corbetforcheckingandimprov− inganearlierdraftofthispaper，andMissDaphneM．Hillsforlocatingthe field notes of M．P．Anderson housedin the British Museum（Nat．Hist．）．

This work was partly supported by a Short Term Visitor Grant from the

SmithsonianInstitution，the KarlP．Schmidt Fund ofthe Field Museum of NaturalHistory，andthefundof“0verseasScientificResearchGrantfor1982 （62041089）and1983（63043061）”deliveredbytheMinistryofScienceandCulture

OfJapan．

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1519−2806pp． Thomas，0．1907．TheDukeofBedford’szoologicalexplorationineasternAsia．II．Listofsma11 mammalsfromKorea andQuelpart．Proc．Zool．Soc．，London，1906：858−865． Tokuda，M．1941．ArevisedmonographoftheJapaneseandManchou−KoreanMuridae．Trans． Biogeogr．Soc．Japan，4：1−155． Won，P．0．1961．Avi−mammalianfaunaofKoreafromtheviewpointoftheForestryProtection． Inst．Agri．，Minist．Agri．andForestry，Korea：31r135． Won，P．0．1965．StudiesontheecologicalobservationofrodentiainManchuriaandKorea．Rep． Coll．EastCount．Pt．2，Nat．Sci．，Ⅰ：331−422＆III：135−200． Zejda，J．1971．Differentialgrowthofthreecohortsofthebankvole，Clethriono〝砂SglaYeOlusSchreb． 1780．Zool．Listy，20：229−245． ZhuangJin−Nan（ed、）．1983．GazetteerofChina．AnindextotheatlasofthePeople’sRepublicof China．AtlasPubl．Comp．，315pp． Zimmermann，K．1964．ZurS宜ugetier−FaunaChinas．ErgebnissederChinesische−DeutschenSam− melreisedurchNord−undNordostLChina1956，No．15．Mit．Zool．Mus．Berlin，40：87−140． Appendix 斗．−ゾ吊■∴・、、／：：山／J∴／‥ノ Localitynumbersusedthisstudy（seeFig．9），locality，1atitudeandlongi− tude，mOnthandyearcollected，muSeum，andregistrationnumberofallspeci− mensexaminedarelistedbelowfromnorthtosouth．Localitynumbersl−13 areherereferredtoClethrionoクク砂Sγゆcanusandnumbers14−34toEothenonv）S j・．ゞJ／／ノド． 1．Monoma River，Amurland，USSR；49015′N，136019′E；January1930， AMNH85424−29，85436−37，85448−50，85452，85454−55，85458． 2．Jaramtai，Inner Mongolia，China；49012′N，120O24′E，May1935，YIO873 −874． 3．Xia−hinggan−1iang，Heilung−kiang ProvリChina；apprOXimately48030′N， 127030’E；June1935，YIO875−881．

4．Yalu St．，GreatKhingan Mts．，hnerMongolia，China；48030′N，122012′E； No寸ember1934，FMNH46034；July1935，FMNH44353；September1939， FMNH49906；October1939，USNM27055；FMNH49905． 5．NeltaRiver，Amurland，USSR；48019′N，135005′E；February1930，AMNH 85471，85474−76，85480，85483−84，85490，85492−94，85499，85503−05、 6．Hsialing，Kirin ProvリChina；45018′N，127018′E；June1938，MCZ41144； June1937，YIOlO86，1092；October1937，MCZ41145；September1939， FMNH49904．

7．Imien−pO，Heilung−kiangProvリChina；45006′N，128DO6′E；September1914， USNM199643，FMNH43416；October1914，USNM199644−47，199649 −51，199653，FMNH43415；September1915，USNM201255，201258−66． 8．Kaolingtsu St．，Kirin Prov．，China；44048′N，128048′E；June1940，USNM

270556．

9．SungariRiver，60milesSWofKirin，China；43054′N，126030′E；June1913， USNM197β20−24；July1913，USNM197825−28，197831，35，FMNH

43413−14．

10．Tumen River，North Korea；apprOXimately42020’N，130040′E；October 1935，BM1938．8．臥16． 11．Nongsa−dong，North Korea；42002′N，128049′E；May1912，AMNH34023， 34029−30，34035，34038−40． 12．Potai−dong，North Korea；aPprOXimately41O43′N，128022′E；May1912， BM13．5．27．53−54，MCZ15292，USNM197976−77，AMNH34007，34009， 34015． 13．Pochong，NorthKorea；apprOXimately41031′N，128018′E；June1912，BM 13．5．27．56，AMNH34016−18． 14．YaluRiver，150milesuptheYaluRiver，NorthKorea；apPrOXimately400 25′N，124050’E；May1914，USNM199638−41，199642；June1914，199665． 15．Changjon，NorthKorea；38044′N，128011′E；June1929，YIO73．

16．1mile N of Oho−ri，South Korea；38020′N，128032′EiApri11954，USNM 298952−53；June1954，USNM298956．

17．Kumhwa，SouthKorea；38017′N，127028′E；June1952，USNM294648−49； November1906，BM7．6．3．61；July1952，USNM294650，298063；September 1952，USNM298064．

18．1mile W of Tangjonggok，South Korea；38Oll′N，12809′E；April1954，

USNM298954−55．

19．Taegwang−ni，SouthKorea；38011′N，127006′E；March1954，USNM298949． 20．Chip’0−ri，SouthKorea；38008′N，127019′E；June1952，USNM294644−47． 21．3milesSWofYanggu，SouthKorea；38006’N，128000′E；April1954，USNM

298950−51．

22．Chang Amトri，Idong Myon，South Korea；38003′N，127012′E；February

1974，BM75．806；November1973，BM75．802；December1973，BM75．803

−805．

23．Ori−dong，SouthKorea；38003′N，126058′E；September1952，USNM298067． 24．Ch’ongsong−ni，South Korea；38002′N，127′09′E；September1952，USNM

298065；October1952，USNM298066．

25．3miles SSE Sumil−ri，South Korea；38002′N，127030′E；September1954， USNM29905． 26．Samsimgok−ri，Shinbook Myon，PochonGun，KyonggiDo，SouthKorea； approximately37050′N，127010′E；November1973，BM75．817． 27．KwangnpngNationalForest，SouthKorea；BM37045′N，127011′E；Febru− ary1974，BM75．782−785；March1974，BM75．786−788，75．793−796； April1974，BM75．789−792；June1974，BM75．797−801． 28．NearPup’yong−ni，CentralNationalForest，SouthKorea；37044′N，127012′

148 11〃（川‘一山

E；August1952，USNM298068；November1954，USNM300646．

29．Ilyung−ri，Changhon Myon，Yangju Gun，KyongyiDo，South Korea； approximately37040′N，127000′E；February1974，BM75．807；Apri11974， BM75．808−811，75．813−814；May1974，BM75．815，816．

30．Mun’gyong，110 miles SE of Seoul，South Korea；36044′N，128007′E； November1905，BM6．12．6．89（theholotypeofC7WeOクク砂S YqgulusThomas，

1907），6．12．6．98，100；December1905，BM6．12．6．90−97，6．1．6．101−106． 31．Near Ch’ongju，Chung Chong Prov．，South Korea；36038′N，127029′E；

December1906，BM7．6．3，53−60． 32．10mi1esNofTaegu，SouthKorea；35052′N，128035′E；December1905，BM 6．12．6．107；January1906，BM6．12．6．108，6．12．6．110． 33．Yonggwang，SouthKorea；35016′N，126031′E；May1930，YIO75−76． 34．30mi1esNofPusan，SouthKorea；35008′N，129bO4′E；August1952，USNM 298069．