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Megascopic Symmetrical Metazoans from the Ediacaran Doushantuo Formation in the Northeastern Guizhou, South China

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Megascopic Symmetrical Metazoans from the Ediacaran Doushantuo Formation in the Northeastern Guizhou, South China

    Megascopic Symmetrical Metazoans from the Ediacaran Doushantuo Formation in the Northeastern Guizhou, South China JournalofChinaUniversityofGeosciences,Vo1.19,No.3,P.200-206,June2008 PrintedfnChina

    IssNlo020705

    MegascopicSymmetricalMetazoansfromthe

    11?1?J1r'J??J?EcIlaCaran0USnantU0.0rmatl0nlntne

    NortheasternGuizhou,SouthChina

    WangYue(王约)

    SchooloftheEarthSciencesandResources,ChinaUniversityofGeosciences,Beijing100083,China;

    SchoolofResourcesandEnvironments,GuizhouUniversity,Guiyang550003,China WangXunlian(王训练),HuangYuming(黄禹铭)

    SchooloftheEarthSciencesandResources,ChinaUniversityofGeosciences,Beijing100083,China

    ABSTRACT:InSouthChina,variousmegascopicsymmetricalmetazoanfossilswerefoundinthe

    upperDoushantuo(陡山沱)FormationoftheNeoproterozoicEdiacaran.Theworm

    likefossilis

    characterizedbymoderntaxolocalannelid,formanymetameres,parapodia,onepossibletentale,an

    alimentarycanal,andadorsalvesse1.ThetriradiatediscoidalfossilsbelongtoTrilobozoa,andthe

    octaradiatediscoidalfossilmightbeCtenophora.Allthesefossilsindicatethatthemegascopic

metazoanshaveappearedintheDoushantuoianofEidacaranandimplythatthesymmetrical

    metazoansmusthaveoriginatedatleast550Maago. KEYWORDS:symmetricalmetazoan,DoushantuoFormation,NeoproterozoicEdiacaran

    ,South

    China.

    INTRoDUCTIoN

    Theemergenceofmetazoans,especiallyofthe bilateralsyrnmetricalmetazoan.isanimportantevent intheevolutionaryhistoryofthelife.Sincethe "SnowballEarth"ftheNantuoGlacialEpochin China),theclimatewarmingandthetemperature risingbecamethenecessaryfoundationforthe evolvementsanddevelopmentsoforganisms.The multicellularbiotasfromtheNeoDroterozoic EdiacaranDoushantuoFormationinSouthChina. ThisarticleissupposedbytheScienceandTechnology FoundationofGuizhouProvince(No.J-20062099),the

    StadholderFoundationofGuizhouProvince,andtheSINOPEC Project(No.G0800-08ZS319).

    Correspondingauthor:gzyuewang@126.com ManuscriptreceivedNovember23,2007

    ManuscriptacceptedFebruary11,2008.

    includingtheWeng'anbiotafromsouthernGuizhou (Lieta1.,1998;Xiaoeta1.,1998;Yuaneta1.,1993; ZhangandYuan,1992;Zhang,1989),theMiaohe biotafromwesternHubei(Xiaoeta1..2002;Dinget a1.,1996;Cheneta1.,1994a;ChenandXiao.1992, 1991:ZhuandChen.1984),theLantianflorafrom southernAnhui(Tangeta1.,1997;Cheneta1.,1994b; Bieta1..1987).andtheWenghuibiotafrom

    northeasternGuizhou(Wangeta1.,2007a,2005;Zhao eta1.,2004)areallimplyingthatthemacroscopic organisms.sincethe"SnowballEarth",mighthave distributedwidelyintheYangtzeOcean(Wangeta1., 2007a,2005;Tangeta1.,2006;WangandWang, 2006).Althoughsomemegascopicmetazoansfound intheMiaohebiota(Dingeta1..1996;Cheneta1., 1994a;ChenandXiao,1992.1991)havenotbeen acceptedbecauseofthelackofsomeobvious structuresandexoskeletonofmetazoan(Xiaoeta1., 2002;Yuaneta1.,2002;Cheneta1.,1994a),the

MegascopicSymmetricalMetazoansfromtheEdiacaranDoushantuoFormationintheNort

    heasternGuizhou,SouthChina201

    researchingontheDoushantuoFormationin northeasternGuizhouischaracterizedbymetazoans becauseofthediscoveryofsomemacrofossils (carbonaceouscompression):theWOrlTIlikeanimal,

    characterizedbyannelidinmorphology,with homologousmetameres,parapodia,apossibletentacle, alinelikealimentarycanalthroughthecentreofbody, andafinedorsalvessel;thetriradiatediscoidalfossils withtreelobesattributedtoTrilobozoaFedonkin;and anoctaradiatediscoidalfossilwithacentralareaon thecentreofthediscandfeatherlikeciliaoneight dextralspinningradiateplates,whichmightbe Ctenophora.

    GEUL0GlCALADEVlRUNMENI'AL

    SETTINGS

    InthesectionnearWenghuiVillage(26.5007"N,

    109.0120"E),JiangkouCounty,GuizhouProvince, China,theDoushantuoFormationisabout70mthick, whichrestsconformablyabovethetiUitesofthe NantuoFormationaswellasbelowthesiliceousstone oftheLiuchapoFormation(Fig.1).Thelower DoushantuoFormationconsistsmainlyofctenoid dolomiteandmediumtothickbeddeddolomite(cap

    carbonate),Themiddlepartismainlycomposedof dolomite,muddydolomite,andcarbonaceousshale. Theupperpartischaracterizedbyblackcarbonaceous shale,whichyieldsabundantanddiversecompression wellpreservedfossils,includingAnomalophyton, Baculiphyca,Beltanelliformis,Chuaria,Cucullus, Cyclomedusa,Doushantuophyton,Eoandromeda, Enteromorphites,Flabellophyton,Gesinella, Globusphyton,Jiangkouphyton,Linbotulichnus, Liulingjitaenia,Longifuniculum,Protoconites, Sectoralga,Wenghuiphyton,andZhongbaodaophyton (Wangeta1.,2007a,b,2005;WangandWang,2006; Zhaoeta1.,2004).Thesebiota(theWenghuibiota), whichwereburiedinsitu,livedinawaterquiet shallowseawithlightorevenpooroxygenconditions (WangandWang,2006;Wangeta1.,2005).Onthe basisofbio?-stratigraphicandchemo?-stratigraphic correlationswithwelldatedNeoproterozicsections

    locatedthroughouttheworld,thedepositionalageof theDoushantuoFormationinYangtzeareais estimatedtoliebetween550and600Ma(Knolland Xiao,1999).Morerecently,theUPbzirconagesof

    anashbedabovetheDoushantuoFormationcap

    carbonateandneartheboundaryoftheDoushantuo FormationaswellastheDengyingFormation(the topmostMiaohebiota)inwesternHubeiyieldedages of(62l?7)Maand(555.2?6.1)Ma,respectively

    (Zhangeta1.,2005).Inaddition,theoverlying LiuchapoFormationinnortheasternGuizhouis correlatedwiththeDengyingFormationinwestern Hubei(Wangeta1.,1987;Qineta1.,1984). Z

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    Figure1.Sketchmapsshowinglocationand horizons(c)ofmegascopicmetazoanfossil occurrence,WenghuiVillage(b),JiangkouCounty, GuizhouProvince(a),China.1.Siliceousstone;2. carbonaceousmudstone;3.muddydolomite;4. dolomite;5.ctenoiddolomite;6.tillite;7.1ocation andhorizonofmetazoanfossils.

    SYMMETRICAL??eIfAZOANS

    BilateralSymmetry

    Theworm1ikefossilwithelongatedbody.from theDoushantuoFormationofnortheasternGuizhou,is characterizedbyannelidinmoderntaxologyin morphology.Itiscomposedofmanyhomologous metameres(Figs.2a-2g).Acircularoralcavityis locatedonthefirstsegment(Fig.2b),andasmallanus isattheendofthebody(Fig.20.Acurved

    carbonaceousfilm,elongatedandstick1ike,shoots

    fromthedorsaofthethirdsegment,anddiminishes graduallyfromthebasedistally(Fig.2b).Butit cannotbedistinguishablebetweenatentacleofthe bodyandamacroalgalfragmentpiledup.Itseleventh ortwelfthsegmentbeinglongerthanothermetameres, whichlookslikearing,mightbeaclitellum,a functionofprocreation(Figs.2b,2g).Onthefront

    segmentsofthebody,fromtherearofthesecond segmenttothefrontoftheclitellum,theinter-segment furrowsaresodeepandwidethattheskin

    protuberatestoformparapodia(Figs.2b,2c,and2g). Onthesurfaceofthebody,therearethreedifferent setae:themetamericseta,whichisstraightor substraightneedle?shaped,onallsegmentsirregularly (Figs.2b,2g);thetwinparapodiumseta,whichis straightspinelikeoneveryparapodium(Fig.2c);and theanalseta,whichisofatriangleform,aroundthe

    anUS(Fig.20.Alinelikealimentarycanallinksthe

    mouthtotheanUSandpassesthroughthecentreof WangYue,WangXunlianandHuangYuming

    bodyevidently(Figs.2a,2b,and2d-2g).Abovethe alimentarycanal,thedorsalvesselisfine,elongated, andcurved(Fig.2b).TheWOrmlikefossil,in

    morphology,showsthephenomenonofheteronomous metamerism.Thefrontsegmentsonthebodyaremore evidentthantherearpart.Theclitellum,whichmight beafunctionofprocreation,islocatedinthe fore?middlepartofthebody.Theparapodiawiththe parapodiumsetamightbeafunctionofmovement, andthepossibletentaclemightbeasenseorgan.So theworm.1ikeanimalwouldbeabletoraiseits foreparttosensethesurroundingsandcouldsinuously moveorcrawlonthedepositionalsurface.Inaddition, thedigestiveandvascularsystem,oneoftheprimary characteristicsofannelidinmodemtaxology,could enhancetheassimilationandtransportationof nutritiousmatters,andcouldpromotethemetabolism

oftheanimalbody.

    Figure2?Photographsshowingtheworm-likefossilsfromtheDoushantuoFormationoftheNeoproterozoic

    EdiacaraninnortheasternGuizhou.Ac.Alimentarycanal;An.anus;As.analseta;CI. clitellum;Dv.dorsal

    vessel;Ms?metamericseta;Oc.oralcavity;Pa.parapodium;Ph.Pharynx;Ps. parapodiumseta;Te.

    possibletentacle.Entirespecimen(a),(e),(g);structuresofthebodyforepart(b);detailsoffro

    ntabdomen

    onclitellum(c);therearpartofthebody(d);detailofbody'Send(f).

    MegascopicSymmetricalMetazoansfromtheEdiacaranDoushantuoFormationintheNortheasternGuizhou,SouthChina203

    RadiateSymmetry

    Thetriradiatediscoidalmacrofossilsfromthe

    DoushantuoFormationconsistofacircularplaneand

    threeradiallobesalthoughtheyareofdifferentshapes

    andsizes(Figs.3a-3c).Alargediscoidalfossilwitha

    star-triradiatesymmetry(Fig.3a)issimilarto

    AlbumaresbrunsaeFedonkin,andAn.

    festastankovskii

    FedonkinfromVendianiniteSeaRussia

    (Fedonkin,1984,1976),butitiSacarbonaceous

    compressionandislargerthanthelatterinthe

    diameteroftheplane.Itslobes.elongated

    subtriangleshaped,preservedintheformof

    carbonaceouscompresses.radiatefromthecenterof

    theplane.whereasthepointofthelobeistowardsthe

    edgeoftheplane.Differingfromtheformer,asmall

    discoidalfossilbearsthreefan.shapedlobesonthe

    plane(Fig.3b).SimilartoTribrachidiumheraldicum GlaessnerfromEdiacara,SouthAustralia(Glaessner, 1959),thefanshapedlobesradiatefromthecentreof theplane.0thersmalldiscoidalfossilshavealsothree radiallobes,butthepatternofthetriradiatesymmetry, asatriangle,isconstitutedbythreeovallobesaround thecentraloftheplanebutwithnoradiationfromthe centraloftheplane(Fig.3c).Thesediscoidal macrofossilswithatriradiatesymmetrycouldattribute tometazoanTrilobozaFedonkin(Fedonkin,1985). Figure3.PhotographsshowingthediscoidalfossilsfromtheDoushantuoFormationoftheNe

    oproterozoic

    EdiacaraninnortheasternGuizhou.Thetrlradiatediscoidalfossils(a-O;theoctaradiatedisco

    idalfossils,

    EoandromedaoctobrachiataTangeta1.(di).

    Anothermacrofossil,anoctaradiatediscoidal fossilwithdextralspinningradiateplates,fromthe

    NeoproterozoicDoushantuoFormation,is

    characterizedbymetazoanbutdifferentfrom Triloboza(Figs.3d-3i).Onthedisc,theeightradiate platesconstituteacircularorsubcircularcentralarea inthecenterofthediscandthenextenddextrallyto themarginofthediscanddisappearinthemarginof

    thedisc(Figs.3d,3h,and3i).Thespinningradiate platescausethewaveshapedmarginofthedisc(Figs.

    3d,3C3h,and3i).Betweenbothradiateplates,a smoothandshallowgrooveconnectsthecentralarea tothemarginofthediscandiscommonlychangeless

inwidth(Figs.3d3i).Inaddition,acentralridge

    preservedintheformofcarbonizedcompression coversthecentreofeveryradiateplate(Figs.3d-3g). Manyfeather.1ikecilia,narrowband.shaped,vertical toorsubverticaltothecentralridge,arrangeregularly ontheradiateplatesandpassoverthecentralridge fFigs.3e-3g).Theoctaradiatediscoidalfossilwas reportedtobefoundinonlytwospecimens(published onespecimen)intheMiaohebiotafromwestern Hubei,SouthChina,andnamedEilscaptichnus ichnofossil.kind.butnogenericnatlleandspecific natlle,notypespeciesandholotype(LiandDing, 1996).Tangeta1.(2008)collectedthreespecimensof theoctoradiateorganism(publishedtwospecimens) fromtheupperDoushantuoFormationofnortheastern Guizhou.andnamedasEoandromedaoctobrachia. Tangeta1.(2008)consideredthattheextantgroupof Eoandromedaisunknownintaxonomy.Eoandromeda isabundantfromtheDoushantuoFormationin northeasternGuizhouandmostofthemarewell preserved.Theendpartsofthefeather-likeciliaon theradiateplatesandcentralridges,invarious specimens,inclinetovariousdirections(Figs.3e-3g), therefore.theband.shapedfeather-likeciliumcouldbe interpretedaslameliathatcouldbeformedbysoft tissuesandcouldquiverceaselesslytowardthelong axesofradiateplatetoproduceacurrent.Theeight currentsproducedfromthedextralradiateplategather tocausearotationalflowlookingforfoodsormoving itsbodyupanddowninseawater.Inaddition.the

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