taxonomyofthellenerarθ …1996).pdftaxonomyof/?ぐ7㲐jどz/α,z?θg㲅my必and尺...

9
NOVAHEDWIGIA,Beiheft112 273-281 Stuttgart,January1996 加/zθzlθμΓが j々り戸gar7でyZ)ai尨c旭ぴ ∂zlが1εθccαj畑zlが /zむjEI/凹胱/i肋17j❹z必y TaxonomyofthelleneraRθ∬jd&z,jjθgθ,7,17z,zand尺θたzzmia (Cymatosiraceae,Bacmariopllyceae) by YukioYanagisawa With4figures Abstract.Taxonomyandphy】ogenyorthethefossilmarinediatomFneraR∂sjgljaD{3111kachary&Maheshwari, Z?昭θ印1面Jous6and£θjzμ面aYanagisawaarebrienydescribed.Thethreegeneracanbeplacedinthefamily Cymatosiraceaebecauseo八heirmorphologicalたatures.Thellenera/?r7∬jと//α,Z?昭c)ΓθWaand尺θ砲μ謂沁includefive, nineandthreesPecies,resPectively.Eachgenusiswellcharactenzedbyitsowndistjnctivemorphologiesand geographicdistributionpattemandmまesaseparateevolutiona口nneage.尺θ∫∫ff//£jischaractelizedbylacking transapicalcostae.Both召θgθハフ1η’aand£θたM謂1’αhavetransapicalcostae,but尺友z14脚沁diffbrsfromZ?θgθΓθv血by havingauniquelystructuredmarginajridge.尺θ∬jE//αandZ?θgθmWαareoceanicanddis❼butedmainlyinwarmwater areas.lncontrast,尺θ治jm必isrestrictedtoneぼ-shoreuPwellingregions./でc7∬jE/・appearedinthelatestEarly oligoceileandbecameextinctintheLateMiocene.Z?θgθΓθ14abranchedfromRθ∬iE/lainthelatest011goceneand makesalonglineageintothePleistocene.££庇田,1沁descendedfromZ7θぎりmlノ沁inth(うhlteEarlyMioceneandsurvived totheendofthePliocene. Keywords.Diatom,taxonomy,mぽinti,fossil,/?卵辿?//a,召θgJθ1ノlj,£f711z£4川1 a. lntroduction /?ag❹/aisalRossilmarinegenuserectedbyDe・;ikachary&Maheshw・1石(1958).Thegenus wasmonotypicwhencreated,t)utlaterithasstl(;cessivelyrticeivedanumber()fsl)eciesand hasbecomeal・cilativelylargediatomgenus(沿rltaining!severalbiostr£ltigraphicallyimportant mafker5;pecies(e・g.Fenner19135,Barron1985). Re・cently,thetaxonomyofthegenushasbeenclarifiedbyG(・rsonde&Schrader(1984), De5sikacharyetal.(1984)andFourtanier(1987).Morel゛c・cently,’1’anagisawa(1994J995a,b, inpreP.)hasestabhsheditstaxonomyonthebasisofふ・tailedmol‘r)hologicandbio- stratigraphicexamination,andhasrevealedthatthegenus尺θ∬泌//αshouldbesubdivided intothethreedistinctgenera尺θ∬加//aDesikachary&Maheshwaris.str.,Z?∂g∂ΓθWaJous6 and£θ吃£4用心Yanagisawa. Thispaperwillbrienyoutlinethetaxonomyandphylogenyofthethreediatomgenera. D{itailedmorphologyandphylogenyofthethreegeneraaswellastheirevolutionarylineage arepresentedinYanagisawa(1994J9¶)5a,b,inprep.)。 Taxonomy Thellenusμag❹/awasestabHshedbyDaikachafy&MaheshwElri(1958)basedon尺ag❹- /αρと7/a7cどa(Grunow)asthetype,whichwasoriginaHyd(jscribedas&θ∫油心?ρと7/a7ca7 0078-2:238/96/0112-0273$2.25 01996J.CramerinderGebriiderBomtraegerverlagsbuchhandlung D-14129Berlin・D-70176Stuttgart

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Page 1: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

NOVAHEDWIGIA,Beiheft112 273-281 Stuttgart,January1996

加/zθzlθμΓがj々り戸gar7でyZ)ai尨c旭ぴ

∂zlが1εθccαj畑zlが/zむjEI/凹胱/i肋17j❹z必y

TaxonomyofthelleneraRθ∬jd&z,jjθgθ,7,17z,zand尺θたzzmia

(Cymatosiraceae,Bacmariopllyceae)

by

YukioYanagisawa

With4figures

Abstract.Taxonomyandphy】ogenyorthethefossilmarinediatomFneraR∂sjgljaD{3111kachary&Maheshwari,

Z?昭θ印1面Jous6and£θjzμ面aYanagisawaarebrienydescribed.ThethreegeneracanbeplacedinthefamilyCymatosiraceaebecauseo八heirmorphologicalたatures.Thellenera/?r7∬jと//α,Z?昭c)ΓθWaand尺θ砲μ謂沁includefive,

nineandthreesPecies,resPectively.Eachgenusiswellcharactenzedbyitsowndistjnctivemorphologiesand

geographicdistributionpattemandmまesaseparateevolutiona口nneage.尺θ∫∫ff//£jischaractelizedbylackingtransapicalcostae.Both召θgθハフ1η’aand£θたM謂1’αhavetransapicalcostae,but尺友z14脚沁diffbrsfromZ?θgθΓθv血by

havingauniquelystructuredmarginajridge.尺θ∬jE//αandZ?θgθmWαareoceanicanddis❼butedmainlyinwarmwaterareas.lncontrast,尺θ治jm必isrestrictedtoneぼ-shoreuPwellingregions./でc7∬jE/・appearedinthelatestEarly

oligoceileandbecameextinctintheLateMiocene.Z?θgθΓθ14abranchedfromRθ∬iE/lainthelatest011goceneandmakesalonglineageintothePleistocene.££庇田,1沁descendedfromZ7θぎりmlノ沁inth(うhlteEarlyMioceneandsurvived

totheendofthePliocene.

Keywords.Diatom,taxonomy,mぽinti,fossil,/?卵辿?//a,召θgJθ1ノlj,£f711z£4川1’a.

lntroduction

/?ag❹/aisalRossilmarinegenuserectedbyDe・;ikachary&Maheshw・1石(1958).Thegenuswasmonotypicwhencreated,t)utlaterithasstl(;cessivelyrticeivedanumber()fsl)eciesand

hasbecomeal・cilativelylargediatomgenus(沿rltaining!severalbiostr£ltigraphicallyimportantmafker5;pecies(e・g.Fenner19135,Barron1985).

Re・cently,thetaxonomyofthegenushasbeenclarifiedbyG(・rsonde&Schrader(1984),De5sikacharyetal.(1984)andFourtanier(1987).Morel゙ c・cently,’1’anagisawa(1994J995a,b,

inpreP.)hasestabhsheditstaxonomyonthebasisofふ・tailedmol‘r)hologicandbio-

stratigraphicexamination,andhasrevealedthatthegenus尺θ∬泌//αshouldbesubdividedintothethreedistinctgenera尺θ∬加//aDesikachary&Maheshwaris.str.,Z?∂g∂ΓθWaJous6

and£θ吃£4用心Yanagisawa.Thispaperwillbrienyoutlinethetaxonomyandphylogenyofthethreediatomgenera.

D{itailedmorphologyandphylogenyofthethreegeneraaswellastheirevolutionarylineagearepresentedinYanagisawa(1994J9¶)5a,b,inprep.)。

Taxonomy

Thellenusμag❹/awasestabHshedbyDaikachafy&MaheshwElri(1958)basedon尺ag❹-

/αρと7/a7cどa(Grunow)asthetype,whichwasoriginaHyd(jscribedas&θ∫油心?ρと7/a7ca7

0078-2:238/96/0112-0273$2.25

01996J.CramerinderGebriiderBomtraegerverlagsbuchhandlung

D-14129Berlin・D-70176Stuttgart

Page 2: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

274 YukjoYanagisawa

GrunowinVanHeurck0883),lnthelS)110’s,thellenusjRagje面(;ontainedanumberofconstituentsincludingspeciesthatassignednowtothegenera/?θgθy∂v必and£θたM琲血

(Ge51’sonde&Schrllder1984,Desil(ε1charyetal.1984).Re・cently,how(うver,thegenushasbeendividedintothreegenera/?θ∬jE//αDesikachary&Maheshwaris.str.,召θgθΓθy加Jous6and

尺θた£4謂必Yanagisawa,andtherefore/?θ∬ね?//αnowcomprisesonlyfivesp{5cies;μθ∬fE//a

砂謂琲どzMcαFenner,μ.戸zlμどraEYanagisawa,/?.か尉・応❹どrと7EYanagisawa,瓦ρ❹どαcどα

(Grunow)Desil(ε1chary&Maheshwariand凡6・/cm即忽(Barron)Desi1(achary.召()JJ(7zpWαisagenusere・ctedbyJous6G973)柘r7ja即り1面々庇7面zldous6.Thegeneric

(kfinitionofthisgenushasbeenemendedbyYanagisawa0995b),andnowthegenusis

composedofeighい;pe(jes;召θg匹θ嶮7gθz?1加皿Dein(achary,召.w❹a脚加jJous6,召.わαΓm㎡f1`′anagisawa,召./?£4zlcrfc❹aMYanagisawa,7?.71とかraM` fanagisawa,召.&z7cEμ❹α(Schrader)

1′anagisawa,Z?.cljnノαMYanagisawaand7?.ρ771印£7/ぞ?acEa哨chrader)Jous6.

Thegenus£り治4面αhasbeenr(うcentlyproposedbyUlnagisawa(1994)basedon

£り治4面aa面ω削Azpeitia)Yanagisawaasthelgener沁type.ltisasmaHgenuscon・sistingofthree5;pecies,£.ど7jαΓ❼(Azpeitia)Υε1nagisawa,尺誠治aどylnagisawaand£.r£zr∫朗θ-

Xこ・4(;/lfa出(Koizumi)Yanagisawa.

Morphology

Thecommonmorpholollytotllethreegenerai・;(lescribedfollowingYanagisawa(1994).The

valvesofthethreegeneraarelineal゙ jElnceolateinoutline(Fig.1A).Bothapiceshaveapical

p()refields(ap)consisting()ffinel)tJncta.0nbothmarginsarernl11` ginalridges(m)whichareclassifiedintofourtype・s(Fi11.1B).Typelisas叩111` ate-typemarllirlalridgewithasinglelongitudinalrowofpores.Theremainingthreeareoffused-typeswheremarginalridgesof

twos;iblingvalvesarecompletelyfusedsothatapair()f7fusedsibhngvalves(ps)seemsasif

asinglefrustule(Fig.IA)・町pes2and3marginalridgeshavetwoandthreebnがtudinalrowsofpores,respectively.Type4hastworowsofporesandresemblestothetype2,but

cleaflydistinguishedbyhavingacribrum-likesiliceouslayeracrosstheporeandafaintsuturelinebetweentherowsofpores(denotedas“sP’inFig.1B).Thecribrum-likelayeris

uniquetothetype4marginalridge.

Specieswhichhavefusedtypemarginalridgesmayformalongchaincolonybythefusionoftheirmarがnalridges(Fig.IA).lncontrast,sr)ecieswhichpossesseparate-type

marginalridgemaybesolitaryinlifeform.’171‘11nsapicalcostae(tc)arede・velopedinZ?t7J汐り1面and£❼zg❹α,butlackingin

μ∂∫j❹/α.Anadditionallongitudinalcostaparalleltothesideispresentonlyin£.a友治αど.

Arimoportula(r)ispresentin“onepercellpattern”,namelyasinglef71・ustuleconsistsof

aprocessvalveandanon’processvalve,andthusthefrustuleisheterovalvate.Therimoportulaislocatedonthevalvefaceatsubcentral,apicalorcentralpositions(Fig.1C).Thespecieswhichmakeacolonychainwithtypes2,3and4marginalridgeshavea

subcentralrimoportulawithoutexception.Thesubcentralrimoportulahasanextemalpore

(or)onthemarllinalridge(Fig.1A).Theapicalorcentralrimoportulaareobservedonlyinsom(うsl)ecieswithseparatedtypenlargirlalridgc・s㈲pel).

Theareol£1elshowaw旧erangeofvariationirlize.Thelsizeof7areolaeゝ 4′£lsclass;medintofiveranksfor(hcription膠anagisawa1994):coarse(ca.1.2-1.5卜mindiameter),medium

(ca.0.8μmindiame5ter),fine(ca.0.4-0.5卜mindiameter),veryfineareolae(lessthanO.11Jmindiame・ter)andtheabsence()fare()lae(11)/ahne).

Page 3: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

Taxonomyof/?ぐ7∬jどZ/α,Z?θg∂my必and尺❼仙詞血

●S●S Types

べ ⊇ ⊇ ⊇ ラ1

べ ⊇ 三 和

嘔 言 言 かps{→4

SV

べし□ソΥ

Λ川Oダ

CΛOい回と

(z:Subcentral

β:Apical

T:Central

275

Fig.1.Mo11)hologyoffrustuleofthegeneraj?rJ5,y・・Ejla,ぶq・7ml’・・rjlldA’rJiz四1・・a(afterYuagisawa1994,1995b,

partiallymodined).-A.Frustuleofβ昭amv沁/7lzzl(がa/αlaYanrlgisawa.m:marginalridge,ar):叩icalporefield,a:£lniola,r:innerapertureofrimoβ)rtula,er:extemalporeofnmoportula,ts:transapicalcosta,ps:apairoffusedsibling

valves,c:cingulum,f:afrusttlle,sv:separalevalve.-B.Typesofmarginalridges,s:singlevalve,ps:pajroffused

siblingvlllves;s1:sutureline.-C.LocationofrimoPortula.

Morphologiccharilcteristics

Thegnera/?(75肩ど//£7,召θgθzlθWαand£θ虹4肌必bearcloseresemblancetothegenerainCymatosiraceaedefinedbyHasleetaL(1983)suchasCymがり肩raGrunowandCaz71/7y/ajz‘α

GrunowinvanHeurckbecausetheycommonlypossess皿nerallydipolaroutline,chaincoloniesconnectedbymaITlginalridgeorlinkingsPines,rimoPortulainthepatternofoneper(;ell,thel)R5senceofocellusorapicalporefieldateachaPex.Thethreegenerathereforecan

beplacedinthefamilyCymatoska(;eae。

Morphologic(;11£1racteristicsofthethreegeneraaresummarizedinthefollowinlls.The

genus/?θ∫∫jど//αischaracterizedby

(1)theabsenceoftrar11;al)ical(;ostae,(2)type3ortypelmarllinalridge,(3)variablepositionsofrimoportulae,

(4)coarseareolaeand(5)theabsence(球longitljdinalrows()1゙ 21reolae.

Themostimportantfeatureof/?θ∫仙?/必istheabsenceoftr2lnsapicalcostaebe(;ausethisfeatureclearlydistingtlihesthegenusfromβ昭・s’りyfaand£θたμM沁。

Withinthellenus/?£7∬fど//α,eachs;r)eciesisdistingtlishedfromeachothermainlybythe

tyPeofmarginalridlle,th(うlocationofrimoportulaandvalve()utline(Fig.2A).Thegenusisdividedintoolderandyoungergoupsmainlybythetypeofmarginalridge;theoldergroup

Page 4: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

276 YukioYanagisawa

’も’心ミミ`-゙

ノyJUj.叱

lUmNwJ 

wnN

9JtlJ011 111 j j  1 1101一

E j jl ol  l 15 3

NEI j ji l

141J oljl 1 .k

ホ{    宍ノゾ

ム出11  0111  0111  11  oll ol  1 1 1 lo 1 lo 1 ol 1 1 1 1 1 j

W m11 1  j ol 1  o l  1101 

Fig.2.valveoutlineandcharacteristicmorphologyofeach4}cciesinlhegenera尺£JjiE11a,S,ノg∂几Jiaand£θjz£j剤ja

(afterYanagisawainprep・d)artiallymodined).Numberbeloweachngurein(licatc・sthetyPeofmarginalridgeofthespecies.Arrowsindicatetheancestor-descendantrelationships.-A.Figuresof/?θ∬1?//asPeciesdemonstratethe

locationofrimoportula.Areolaeareomittedforsimplincation.-B.RguresofZ?θgひmv心sPeciesshowtheareolaesize

ineach叩ecies.Transapicalcostaeareomitted.-C.Figuresof尺❼za用心speciesdemonstratethepattemoflhe

transapicalcostae.ARiolaeafeomitted.

includingR.尽朋朋どrrjcaandj?.jrlz7どraどhasthetype3marginah・idge,whiletheyounger

groupe(/?.ルarM雨a77ど,瓦/7❹どaceaand/?.ど/∂ylgaだ7)ischaracterizedbytypel.lntheolder

group,7?θ卵加//a砂肌房drfcaisdistinguishedbyitslinearvalveoutlinefrom/?.μnzlどraごwhichhaslin{5arlanceolateoutline.Ivithintheyoungergroup,ノ?.ル14rla❹どraど(litTersfromtheothertwomembersbyitsbroadisopolarvalveoutlineandthecentralrimoportula.

&apicalpositionofrimoportula./?θ∫jど//aど/θ丿7ga忽resemblestoμ.ρ❹εαcどα,butdiffersbyitselongatedvalveandthesubcentralrimoportula.

ThelgenericcharacteristicsofZ?θg匹θlノ必are

(1)thepmsenceofwe11’develoPedtansapical(;ostae,(2)thetM)e3ortype2ma昭inalrid琲三

(3)thesuk氾ntralrimoportula,(4)mediumtoveryfineareolaeorthe£lbsenceof£1reolae(hyaline)and(5)therandomarrangementof£lreolaeiff)resent,notforminglongitudinalrows.

Page 5: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

Taxonomyof尺,フ∫肩ど//どj,Z?θgθ印w‘aandA’(がzμ,η必 277

&JgθΓり1ノjαcleallydi汀ersfromj?θ∬jど//abyhavingtrilnsapicalcostae.lntermsofthe

?lm皿ceoftrar11;apical(;ostae,Z?θgθm1ノ訟has()t〕viousaffinitieswith£θ扨4肌訟,butis(listinlluishedbythetypeofmarがnalridge;theformerhasthetype3ortype2marginalridge

wh{う2asthelatterPol;sessesthetype4margin£11ridge.

WithinthegenusZ?昭匹θ1ノ血5;peciesareclassifiedbyareolaesize,typeofmarginalridge,valvesizeandvalveoutline(Fig.2B).Th(5lineageofthegenusZ?θgθmWαcanbesubdivided

intoolderandyoungergroupsbyal` eolaesizeandthetypeofmarginalridl哭.Theoldergroup

consistsof召.gθ肌/7θ∬f,召.w❹a訴加j,召.わarrθ雨j,召.ρμyz(?rjc&4/aMand召.zlと?∫zraだz,aHofwhichpossessareolaeonthevalvefacewiththetype3marginalridge.0nthecontrary,the

youngergroupcomposedofS.た7yl(7どrr❹a,召・戸raEp❹a7ceaand召.cμn゙ aMcompletelylacksareolaeandhasthetype2marginalridge.lntheoldergroupof召θgθΓθ1ノ血,eachspeciesis

distinguishedbytheareolaesize,valvesizeandvalveoutline.Z?θgθ印v訟gθ肌わθjjand召.w❹a訴f㎡aredifferentiatedbytheareolaesize;Z?.gθ訴わθ肩fhascoarserafeolae.召θgθΓθv訟

かar政7雨jhastheareolaeofthesamesizesasthoseof召.1ノど雨a訴丿雨,butdiffersbysmaller

valvesize.召θ呂θΓθy血ρ附lcz加❹aた7isdifをrentfrom召.わar印成fbymuchsmallerareolae.Z?θgθ印1ノjαΓθ∫rΓαΓaresemblesto召.βa71(7rfc14Za凶,buthasbroadervalveandmorel・ostrate

apices.lntheyoungergroup,召.μΓaごρ❹どacどαisdistinguishedfromZ?./a71cどμ❹abylargervalvesize.Z?∂gθmWαcμnノαΓαhasamnitieswith召./aμ(7εμ❹a,butclearlydi汗ersfromthe

latterbyitscurvedvalveoutline.

£θ吃lj訴訟istypifiedby

(1)thei〕1‘{isenceoftrarls;apic211costae,(2)type4marginalridge,

(3)subcentralrimoportula,(4)mediumareolaeinsizeand

(5)theareolaearrangedilongittldinalrows.

Thegenus£θ治4謂訟dif秘rsfrom/?∂∬泌//abyhavingtl-arlsapicalc()stae.Becauseofthe

l)r{うsenceoftransapicalce;tae,£∂治4訴訟seemstobeverysimilarto召θgθzlθWaeisl)ecianyinLMobservation,butitis(listinctbyhavingthetyPe4marがnalridgewhichisuniquetothis

genus.訊戸ithinthegenus,eachspc5ciesisdistinguishedbyvalveoutlineandthefeaturesoftrans-

apicalandlonがtudinalcostae(Fig.2C).£θたM用心a&7印fand瓦rと7r∫&4ylθた£4c/z1?7?∫むare

differentiatedbyvalveoutline;thelatterspecieshasmorerostrateapices.尺θ吃μ訴訟a友治aどdiffersfromthetwospeciesbyhavingcontinuoustransapicalcostaeandanadditional

longitudinalcostaalongthemargin.

Geographicdistributjon

Previouslyreportedgeographicoccurrencel;indicatethatthethreegeneratreatedinthispaper

showdistinctllc;()graphicdistributionpattemchara(;teristictoeachgenus.Thesl)eciesincludedin尺θ∬泌1/αhavebeenreportedmainlyfromoceanicwarmwaterrellionssuchasthe

equatorialPacificandc5quatol″iallndianoceanswithrareo(;(;urrenceinthemiddle-latitudes

(Yanaがsawa199511)JimilarlyZ?c7j汐mv血specieshavebeendesribedmainlyinthelow-latitudergions(Yanagisawa凶95b).Thetwogenera,t㎞7efore,maybe()ceanicinnature

andmainlyditributedinwarmwatcうにegi()ns.0nthecontrary,themembersofλ7θ治4面ahaveneverbeenrc4)ortedfromoceanicrgiorlssuchastheeiquatorialPacificOceanwhere

/?θ∬泌//aand召∂gθmWaoccurElbundantly,butmainlyinnear-shoreoron-landsequencesintheworld,andthus尺∂吃μ加沁appearstobecomposedofneaf-shores;I)ecics.Furthermore,

Page 6: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

278 YukioYanagisawa

Age

Ma刄θ∬jd/α 召θgθΓθl盾z 瓦θたzz謂必

5 -

10-

15-

20-

25-

30-

-・E

「|

-

1i l lMi , l j

] § J ヨ伺 J

∩ 隷召 川 仁べ ■ ■ ・言 ・ ヅ ] ] 鴇り ・ 、 1 ‘ ‘ ‥ ‥i 訂 ] ] 腿 回

S ミ ヅ 石 - § 1j J ‥ L i に反 。 I R4 ゛ 土 色 1 、

1 1 ミ1 1 ぎ か居 ]ご r ¬ : j . 、

ヨ●-

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回SOiQ-召i

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栽 ズ ニi

土 蔵=j店’Eミ

七 = 咄匂 j `回

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Fig.3.1;tratigraphicrangesandevc)lutionafyheageofthellenera硲J.y.y,・。1/a,ZI,JjμJrr,,面and£aj3.ja(aner

YanagisawajnpreP.)。

Page 7: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

Taxonomyof&,,?511,?//a,βθμθz7川心and尺r7吃な用心

WJ  1  1  1 ol ol ollj19111EI

5ljnmillll 511 1194112111141  llRI・・‘

OEl jlE

jll麗y

尺θ

l  1  11 011 l ll l l l l l l l l 11111 l l 111111 S

j11111 ojl  ojjljjli11110111111111111Roo

刄θ∬&?//α

Fig.4.Morphologicalchangeinthe{2volutionofthe

lleneraR乙同地?//a、Z?θg匹θy血and£r丿1・z脚川・a(afterYanaがsawajnprep.).

IJ一i四yU 01111

 mE

1 j tUjil  11110101011001 01101 11  12 

vjj 11118 1111E9

279

召θgθΓθμα

£∂た£j用心sl〕eciesmaybeupwelling!;l〕eciesasirldicatcdbythedistin(:ttendencytooccurmoreabundantlyinsuchupwellingregionsaso仔Caほomia,o汀Peruando汀westAfrica

(Ulnagisawa1994,FourtanierlS)87)。lnsummary£θたμ用心clvidentlyshowsas;ilgnificantlydi汗erentgeograPhic(hstribution

r)atternfrom/?∂∬jE//aand召昭(?7iど7Wa;theformerisrle5ar-shoreupwellinggroup,whc5aasthelattertwogeneraaree5!;5;entiallyoceanicandmainlydistrit)utedinwarmwaterareas.

Phylogeny

ThePhylol;{うneticrelati()nshipsbe5tweeneachsl)eciesofthにhreegeneracanbedetcうrminedbymol‘phologyand琲ε1tigraPhicrec()rds(F゙ igs.3,4).

Thediatomplexuscomposedofthethreegenerawasestablishedasadistinctdiatom

groupbythelatestEarlyO卯ocerlc・(Fig.3).Th垂法sリenus/?りお❹/αstartedwith/?.砂mmE,ΓμcainthelatestEarly011gocene./?∂∫乱ど//a砂川所以バcaevolvedinto/?.戸几77どraEintheLate

Page 8: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

280 YukjoYanagisawa

Oligocenewithanillcreaseinsizeandachangeinvalveoutlinefromnnearliomtolinear-1ε1nceolateshal)e・(Fig.4).lnthe(・ε1rliestMiocene,/?.戸zμ1どraどdevelopedinto/?.ル14rΓα雨どraど

bythet:・madeningofvalveoutline,achangeofma咄nE11ridgefromafu・;e・d-type(type3)toasepafated-type(typel),andthernigrationofrimoportulafromasubcentraltoacentral

position.Theevolutionarychangefromμ.ル£ぴra短どraどto/?./7❹どαcどαismarkedbythedeveloPmentofheteropolarityinvalveoutlineandthemigrationofrimoportulafroma

centraltoanapicalposition.lntheMiddleMio(;ene/?θ∬jど//aど/θngara,thelastmemberof

thegenus,developedfrom/?./フど7/どacどabytheelongationofvalveandtherecu町enceofrimoportulatothesubcentralposition.ThislineagebecameextinctduringtheLateNliocene

withoutleavinganydescendants.Thegenus召θgθz7)y加makesalonglineageleadingfrom召.gθ初占θ∫jfto召.cμn/a耀via

召.w❹a初j❹,召.かα汀∂雨j,Zj.paμ(?だc❹αZど7and召.&μ(7ど侑4/αwithtwoshortbranchesto召.zlり肩raMandZ?・Fa叩乙7&ac凹(Fig.4).lnthelate(叫lgocenethegenussplitsfromthefore-

going/?θ訂jど//αwiththeevolutionofZ?・g∂扇加盾from/?θ∬泌//a砂z71MEびjcαassociatedwiththedeveloPmentoftransapicalcostae.Bytheendofthelateoligocene,S.w❹α肌加jevolvedfrom召.gθ初わ∂∫ffbyadecreaseinsizeofareolaeandthecompletedevelomentoftransapical

(;()stae.lntheearlyMiocene,Z?.v四血肌加fgaverisetoZj.かarrθ❹fbyade5(;reaseinsizeofvalve,andth{うreElfterthelatterspeciesevolvedintoR/フ附7d泌❹αMbyasizereductionof

areolaefromnnetoveryfinesize.From召./7脚1(ご瓦c❹ど7ra,Zj.印∫rraだzdevelopedbymaking

stronglyrostrateapices.Z?θgθ印以・ど7芦仇c7rjc❹α忽showsgradualreducingindensityofareolaeonthevalvefaceduringtheEarlytoMiddleMiocene,andl-esultedinthecreationofthe

hyalinevalvefaceof召./azl(7どrr❹a.From召./£7月cごrr❹a,theevolutionarylinebranchedintotwodirectiom;.Thefirstlinewas召./フra印❹eaca7whichevolvedfrom召.Z£7ηcどrr❹abyan

ir心reaseinvalves吃e.Thesecondlinewasl?.cMnノaMwhichdevelopedfromS.たz71cどΓμ4/£7by

makingacurvedasymmetricvalveoutline.Thegenus£❹弘初必isasimplelineageconsistingofonlythreespecies.ltbeganinthe

earlyMiocenewiththeevolutionof£.aどyamffromZjθg∂印1ノ必&と7仔θ雨f.lnthelatelvliocene,

thelineagesplitsintotwobl’anches.尺ど7だ治aEevolvedfrom£.α&7印jwiththedevelopmentofcontinuoustransapicalcostaeasweHasthelongitudinalcostae.Atalmostthesametime

£.rど7な1477θん£4c/治?心なdescendedfrom£.ど7ja印f,withtheapicesbecomingstronglyrostrate.A’θ治4初必た7r∫£4zlθた14c垣ど心むbecameoneofthe(1£汀acteristicmembersofthePhocene

middle-latitudediatomassemblage,butunderwentextinct,terminatingthisphyleticlinenear

theendofthePhocene.

Summary

Morphology,taxonomyandphylogenyofthethreediatomgenera/?θ∬fd/α,召θgθΓθlノ血and

尺θ砲£4謂血aredescribed.ThethreegeneraareplacedinthefamilyCymatoiraceaeHasle,vonStosch&SyvertsenbecauseoftheirmorPhologic弛atures./?θ∬f❹/acomPrisesfivespeciesandischaracterizedmainlybylackingtransapicalcostae.Z?θgθmWα,consistingofnine

speciesjsthelargestofthethreegenera,characterizedbyhavingtransapicalcostaeandtype

3ortype2marginalridge.尺❼弘規必isasmaHgenuscontainingonlythreespc5cies.The

genusshowscloseresenlblanceto/?θJlcμm万a,butdi汀ersbypo!;sessingtype4marllinalridgethatisuniquetothisgenus。

Eachdiatomgenusshowsadistinctl;e5ographic(jistributionpattem./?θ∫ijど1/aand召θgθ-mv必arecうs5;entiaHyoceanicandmainlydistributedinwarmwaterareas.lncontrast,だり吃μ-

脚血iscomposedofupwelling5;peciesd心ributedn{iar` shoreregions.

Page 9: TaxonomyofthelleneraRθ …1996).pdfTaxonomyof/?ぐ7㲐jどZ/α,Z?θg㲅my必and尺 仙詞血 S S Types べ㱫㱫㱫ラ1 べ㱫三和 嘔言言か ps{→4 SV べ し ソ

Taxonomyof/?ay∫fと//a,SθgθΓθ1jaaJld£r7迂回yl沁 281

ThefirstlineagejRθ∬jE//aappearedinthelatestEarly011goceneandb!5cameextinctintheLateMiocene.召θgθ印v沁splito汀fromtheforegoing/?θ∬泌//ainthelatest011gocene

andmakesalonghneageintotheMiddlePleisto(;ene.£θ吃μ琲必derived斤om召θgθ7り1ノjain

thelateEarlyMioceneandsurvivedtotheendofthePliocene.

Acknowledgements

lwouldliketoexl)ressspecialthaJ11(stoFumioAkibaandltaruKoizumiwhoenc()uragedmetostudythisllcinus.lamvery11r£ltefultoJohnA.BajTonandElisabethFourtanierfortheircriticEllthoroughreviewoftheveryeaflydfaftofthis

manuscriptandtheirhelpfulstll;gestiononulxonomy・

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Author’saddress:

YukioYanil画awa,(kologyDepartmerlt,Ge(水)gicaISurvey()fJapan,I↓3Higashi,TR11(uba,lbaraki305,Japan;

e-mililaddress:yanagisa@11・;j・gojp