ComparativeosteologybetweenDiomedea,PhoebastriaandThalasarche (albatrosesformerlysetledin Diomedea )

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1 群馬県立自然史博物館研究報告 (18):35-64,2014 Bul.GunmaMus.Natu.Hist.(18):35-64, 軸宍宍宍宍宍宍宍宍宍宍宍宍宍宍宍宍宍雫 OriginalArticle 軸宍宍宍宍宍宍宍宍宍宍宍宍宍宍宍宍宍雫 ComparativeosteologybetweenDiomedea,PhoebastriaandThalasarche (albatrosesformerlysetledin Diomedea ) MATSUOKAHiroshige 1 andhasegawa Yoshikazu 2 1 DepartmentofGeologyandMineralogy,GraduateSchoolofScience,KyotoUniversity:Kyoto ,Japan. (maca@kueps.kyoto-u.ac.jp) 2 GunmaMuseumofNaturalHistory:Tomioka,Gunma ,Japan Abstract: Four genera,diomedea (greatalbatroses),phoebastria (North Pacific albatroses),thalasarche (molymawks)andphoebetria(sootyalbatroses)arerecognizedinthealbatrosfamily.amongthefourgenera, Diomedea,Phoebastria and Thalasarchewereoncecombined in alargergenus Diomedea morphologicaly. OsteologyalsodividesPhoebetriafrom Diomedea andthenthepaleontologicalrecordsofalbatroseshavelongbeen identifiedas Diomedea solely.osteologicalidentificationofdiomedea,phoebastriaandthalasarcheisabigsubject toview theevolutionalhistoryofalbatroses,andthenthisstudyexaminedthecomparativeosteologyofthesethree generabyusingtheosteologicalspecimensofdiomedeaexulans(wanderingalbatros),phoebastriaalbatrus(shorttailedalbatros),p.nigripes(black-footedalbatros),thalasarchemelanophris(black-browedalbatros)andt. chlororhynchos(atlanticyelow-nosedalbatros).asaresultofourstudy,diomedea,phoebastriaandthalasarche canbeidentifiedbytheseosteology.totaly73distinctionpointsontheirmajorskeletalelementshavebeenrecognized. Amongthe73points,DiomedeaandPhoebastriashare60commonfeatures,andform acladeincontrasttothalasarche. OnlyonepointwassharedbetweenPhoebastriaandThalasarche,showingtheobviousphylogeneticdiferencebetween them.takingthemorphologyofknownfosilrecordsofunambiguousstem albatrosesintoconsderation,wefoundthat thethalasarcheisthemostprimitivegenusamongthethreegenera,andthatthecladeincludingdiomedeaand Phoebastriabranchedoffrom it.weconsideredphoebetriaasthemostderivedgenusrelativetodiomedea,because9 pointsaresharedbydiomedeaandthalasarcheanduniqueinphoebetria.diomedeaisthelargestandthalasarcheis thesmalest,andthenthesimilaritymightnotbefunctionalconvergenceandmightbethephyleticprimitive characteristics.thisstudywilhelptoidentifythefosilmaterialsof Diomedea tothecertaingenusand,togetherwith thefuturedescriptionofdetailedosteologyofphoebetria,wilbebasicinformationonthephylogenyandevolutional historyofalbatrosfamily. KeyWords: osteology,albatros,diomedea,phoebastria,thalasarche Introduction Albatroses,birdsofanavianfamilyDiomedeidae,arelarge seabirdsbelongingtotheorderprocelariformes.underthemost commonlyacceptedclasification,21recentspeciesofalbatroses infourgenerarangewidelyintheoceanofthesouthernhemisphereandthenorthpacific.thesegeneraare:diomedea(great albatroses),phoebastria(northpacificalbatroses),thalasarche (molymawks)andphoebetria(sootyalbatroses)(nunnetal., 1996;OnlyandScofield,2007).ItwasNunnetal.(1996) molecularbiologicalworkstudyingthemitochondrialdnaof 14acceptedspeciesthatfoundfourmonophyleticgroupswithin Diomedeidae.Theyalsofoundthetwolinageswithinthem:a cladeincludingthegreatalbatrosesandthenorthpacificalbatrosesandtheothercladeincludingthesootyalbatrosesand molymawks. Amongthefourgenera,Diomedea,PhoebastriaandThalassarche,i.e.otherthanPhoebetria,wereformerlygroupedinthe genusdiomedeaafterthelongtaxonomicaldebateofover100 years(alexanderetal.,1965).thekeymorphologyofthis broadsensediomedea(writenas Diomedea below)isobviously similar. OsteologyalsodividesPhoebetriafrom Diomedea (Figure1),thatmeans Diomedea isobviouslysimilarinits osteologytoo.paleontologicalstudiesdependingontheskeletal materialthereforehavelongbeenusing Diomedea simply andfewworkshaveidentifiedthesubdividedgenerainfosilrecords.afewexamplesaretheosteologicalworkbydénesand Silveira(2007)andpaleontologicalworkbyOlsonandRasmusen (2001),andthescantinesisabigproblem.Now,toreconstruct theevolutionaryhistoryofalbatroses,paleontologistsmusttryto preciselyidentifythebirdstodiomedea,phoebastria,thalassarche,oranextinctgenus. Asthefirststep,weexaminedthecomparativeosteologyof Diomedea,Phoebastria and Thalasarche and investigated whetheritisposibletodistinguisheachgenusfrom itsmorphologybyusingtheskeletalspecimensofdiomedeaexulans (WanderingAlbatros),Phoebastriaalbatrus(Short-tailedAlbatros),Phoebastrianigripes(Black-footedAlbatros),Thalasarchemelanophris(Black-browedAlbatros)andThalasarche chlororhynchos(atlanticyelow-nosedalbatros).asaresult, wefoundtotaly73distinctionpointsonelevenmajorskeletal elements,whichshow highsimilaritybetweendiomedeaand Submited:February14,2014.;accepted:March10,2014.

2 36 MATSUOKAHiroshigeandHASEGAWA Yoshikazu PhoebastriaanduniquenesofThalasarche. Ourresultindicatesthateventhefosilizedskeletalelement, ifthefosiliswelpreserved,couldbeidentifiedtothecertain genus.thisstudycouldnotincludephoebetria.whenthefuturestudydescribestheosteologyofphoebetria,thesenotes wilopenawaytoreconstructthephylogenyandevolutional historyofalbatrosfamily. MaterialandMethods ThegeneticclasificationofNunnetal.(1996)isfolowed. Thenotation Diomedea isusedforthecaseswhenthename DiomedeaisusedinthesenseofAlexanderetal.(1965).OsteologicalterminologyfolowedBaumelandWitmer(1993), VondenDriesch(1976)tomeasure,and,partly,Howard(1929). Totalytwelveskeletalspecimensofalbatrosiswereobserved. Theyare:1Diomedeaexulans,2Phoebastriaalbatrus,2Phoe- Figure1.TheskeletalelementsofPhoebetriapalpebrata. ComparetotheonesofDiomedea,PhoebastriaandThalasarcheshowninplates.A: thedorsalviewofcranium.b:theventralviewofsternum.c:thedorsalviewofrightcarpometacarpus.d:thedorsalviewofrightcoracoid. E:thedorsalviewofpelvis.F:theanteriorviewofrightfemur.G:theanterior(dorsal)viewofrighttarsometatarsus.H:theanteriorviewof righttibiotarsus.i:thecaudalviewoflefthumerus.drawnfrom thephotosofthespecimenhousedinthedivisionofbirds,smithsonianinstitution,numberedusnm ThephotosweresuppliedbyMr.J.Watanabe.SomeuniquefeaturesofPhoebetriaagainst Diomedea genera,suchas:verynarowtomia,extremelyshortandwidesternum,shortandlateralylongcoracoid,thedorsalsurfaceofcoracoidisvery pneumatic,straightfemur,relativelyfattibiotarsus,sunkenlateralandmedialwalofshaftoftarsometatarsusandthentheendsofthisskeletal elementexpandwel,lowandburlyproc.supracondylarisdorsalisofthedistalendofhumerus,etc.arevisible.

3 Comparativeosteologyofalbatroses 37 bastrianigripes,4thalasarchemelanophrisand3thalasarche chlororhynchos.usingthepluralspecimensofeachspecies,exceptford.exulans,wecheckedtheintraspecificvariationatfirst. Basicaly,everyspeciesshow verysimilarmorphologyand thenweconcludedthattheintraspecificvariationisnotserious. Becausesomespecimenshavedriedtendonsandotherfleshy materialsstuckonbones,onlyonespecimenforeachspecies wasusedinfolowingobservationsandmeasurements. Thespecimensusedinthisstudyarealinthecolectionof PaleontologicalLab,DepartmentofGeologyandMineralogy, KyotoUniversity(KUGM):KUGM-RA13008,maleDiomedea exulans;kugm-ra99119,phoebastriaalbatrus,sexunknown; KUGM-RA14001,Phoebastrianigripes,sexunknown;KUGM- RA13009,Thalasarchemelanophris,sexunknown;andKUGM- RA13012,maleThalasarchechlororhynchos. Measurements:FolowingVondenDriesch(1976),somepoints weredefinedinthisstudy(asteriskedinfolowinglist).details ofthemeasurementsareasfolowsandgiveninfigures.cranium (Figures2,3):BC1*,culmenalbreadth1,breadthoftheculmenal ridgeatthewidestpoint,usualyatjustanteriortotheexternal naris;bc2*,culmenalbreadth2,thebreadthbetweentomiaat thepointofbc1;bc3*,culmenalbreadth3,smalestbreadth oftheculmenalridge,betweenexternalnaris;bc4*,culmenal breadth4,thebreadthbetweentheposteriorendsoftomia; CBL,condylobasallength;GB,greatestbreadth;GH,greatest heightinthemedianplane,from thebasitemporaleinthemedian planetothehighestpointofthebraincase;gl,greatestlength; LI,lengthoftheincisivum,from apexpremaxilaristothemost aboralpointoftheprocesusfrontalesoftheincisivum in themedianplane;lp,lengthfrom theprotuberantiaoccipitalis externatothemostaboralpointoftheprocesusfrontalesofthe incisivum inthemedianplane;sbnf*,smalestbreadthofnasofrontalhinge;sbo,smalestbreadthbetweentheorbitsonthe dorsalsurface.mandible(figure3):gl,greatestlengthofonehalfofthemandible;ls,lengthofthesymphysis.sternum (Figure4):GB*,greatestbreadth;GLM*,greatestlengthmeasuredfrom thecranialpointofthemanubrium sternitothelevel ofthemostcaudalpointofsternalplane; LC,lengthofthe cristasterni,from theapexcristaesternitothecaudalborderof themetasternum inthemedianplane;lm,lengthfrom thecranialpointofthemanubrium sternitothecaudalborderofthe metasternum inthemedianplane;sb*,smalestbreadthofthe sternalplane,measuredatthenarowestpart;sbf,smalest breadthbetweenthefacetsforthecostosternalarticulations, measuredatthenarowestpart;coracoid(figure5):bb,greatest basalbreadth;bf,totalbreadthofthefaciesarticularisbasalis; BFm*,breadthofthemedialportionoffaciesarticularisbasalis (=sternalis);gl,greatestlength;lm,mediallength.scapula: Dic,greatestcranialdiagonal;GL,greatestlength. Humerus (Figures6,7):Bda,breadthofthedistalend,measuredonlythe areaofinternalandexternalcondyles;bp,breadthoftheproximalend;gbd*,greatestbreadthofthedistalend,measuredwith theprocesussupuracondylarisdorsalis;gl,greatestlength;sc, smalestbreadthofthecorpus.radius(figure9):bd,greatest breadthofthedistalend; GL,greatestlength; SC,smalest breadthofthecorpus.ulna(figures8,9):bp,breadthofthe proximalend;did,greatestdiagonalofthedistalend;dip, greatestdiagonaloftheproximalendfrom thecaudalborder oftheolecranontothecranialborderoftheproc.cotylarisdorsalis;gl,greatestlength;sc,smalestbreadthofthecorpus. Carpometacarpus(Figure9):Bp,breadthoftheproximalend; Did,greatestdiagonalofthedistalend;Gl,greatestlength. Phalanxproximalisdigitimajoris(Ph.1major.):GL,greatestlength; La,lengthbetweenarticularsurfaces.Pelvis(Figure10):AA,breadth betweenthebordersoftheacetabula,measuredatthenarowest part; BA,breadthacrosthetwoantitrochanters;CB,cranial breadth;dif*,thelongdiameteroftheforamenilioischiadicum;gl,greatestlength,lengthfrom thecranialborderofthe iliatothemostcaudalpointoftheischia;ls,lengthfrom the cranialborderoftheiliatothespinailiocaudales;lv,length alongthevertebrae,centraly;sb,smalestbreadthofthepartes glutaeae.femur(figure11):bd,breadthofthedistalend;bp, breadthoftheproximalend;dd,depthofthedistalend;dp, depthoftheproximalend;gl,greatestlength;lm,mediallength; SC,smalestbreadthofthecorpus.Tibiotarsus(Figure12):Bd, breadthofthedistalend;bp,breadthoftheproximalend;dd, depthofthedistalend;dip,greatestdiagonaloftheproximal endfrom thecondylusmedialisfemoralistothecristalateralis; GL,greatestlength; La,axiallength;SC,smalestbreadthof thecorpus.tarsometatarsus(figures13,14): Bd,breadthof thedistalend;bp,breadthoftheproximalend;dd,depthof thedistalend; DSC*,greatestdepthoftheshaftmeasuredat thepointofsc;gl,greatestlength;sc,smalestbreadthof thecorpus. 1: Measurements (Table1) Results Themeasurementsofexaminedspecimens(species)areshown intable1.amongthefivespecies,diomedeaexulansisthe largestandphoebastriaalbatrusisthesecond.phoebastria nigripesandthalasarchemelanophrishavenearlythesame measurementsandshowsimilarproportion.thalasarchechlororhynchosisthesmalest. Comments:Itistruethatthe size issurelyusefultoidentifythe speciesofavianosteologicalremains,becausethesizevariation issmalinadultbirds.thisempiricallaw,naturaly,hasbeen appliedtothepaleontologyofalbatrosesalso.authorsdiscused thespeciesbasedonthe size,aftertheyidentifiedthebirdto Diomedea.AnauthorofthisstudyHM hasalsoreported oneofthesmalestalbatrostobereported from themiocene ofnagano,japan(matsuokaetal.,2009). The size,however,isnottheplenarymanner.forexample, D. nigripesand D. melanophrisinthisstudyshow about thesamesizeinmeasurements,andthentheyareimposibleto beidentifiedbytheir size only.wemustobservethedetailed morphologytoidentifythem corectly. 2: Distinction points to identify Diomedea,Phoebastria and Thalassarche Totaly73distinctionpointsontheirmajorskeletalelements werefound.oureyesprobablyfocusedonlyonthecharacteristics thatseem tohavehigherpotentialtobepreservedinfosils,and thisnumbercouldbeincreasedinfurtherstudy.

4 38 MATSUOKAHiroshigeandHASEGAWA Yoshikazu Table1.Themeasurements(inmm)oftheosteologicalspecimensofDiomedeaexulans (KUGM-RA13008,male),Phoebastriaalbatrus KUGM-RA99119,sexunknown),Phoebastrianigripes (KUGM-RA14001,sexunknown),Thalassarchemelanophris (KUGM-RA13009,sex unknown)andthalassarchechlororhynchos (KUGM-RA13012,male).AlarehousedinPaleontologicalLab,DepartmentofGeologyand Mineralogy,KyotoUniversity. (continued)

5 Comparativeosteologyofalbatroses 39 Table1.continued Ossacrani (Figures2,3;Plates1,2) Sevenpointshavebeenrecognized. 1)Thetransversalshapeofculmen.-DiomedeaandPhoebastria havefatculmenanditsupperpart,culmenalridge,intransversal section,showsadome-likeinvertedu-shape.thalasarchehas alateralythin,invertedv-shapedculmen.thediferenceof thispointhaslongbeenreportedastheevidenceoftwolineages in Diomedea (Coues,1866). 2)Thepositionofthemaxilarygroove,onthelateralviewof culmen.-diomedeaandphoebastriahavethemaxilarygroove runningnearlyinthemiddleoftheculmen.thalasarche sculmen hasitsmaxilarygrooveatthehighposition,neartothedorsal margin. 3)Theshapeofexternalnaris(osteological).-Diomedeaand Phoebastriahaverelativelyhigh,ovalexternalnaris.Thalasarche hasdorsoventralynarowexternalnaris,withslitsattheanterior andposteriorends. 4)Theimpresionofsaltgland.-DiomedeaandPhoebastria havetheimpresionsofsaltglandsbeingentirelyonthecranium andthentheposteriorpartofthedorsalmarginoforbitistheshelf ofthefrontalbone.thalasarchehasthesaltglandsrelatively lateralylocated,andthenthedorsalmarginoftheorbitiscovered bytheimpresionofthesaltgland. 5)Therostrum parasphenoidalis,intheventralsurface.-diomedeaandphoebastriahavefatandshortrostrum parasphenoidalis. Thalasarchehasaslenderone. 6)Theforamenmagnum.-DiomedeaandPhoebastriahave dorsoventralyhighforamenmagnum.thalasarchehasalateralywideopening. 7)Thequadrate,whenviewedfrom theventralsurface.-dio-

6 40 MATSUOKAHiroshigeandHASEGAWA Yoshikazu medeaandphoebastriahaveanteroposteriorlylongquadrates, andthearticularsurfacetothemandibleistriangular.thalassarchehasshortandflatquadratesinthisaspect. 8)Theapexcarinae.-Thefeatureisobviousintheventral surfaceoftheapex.phoebastriahasauniquey-shaped,lateraly expandedapex.diomedeaandthalasarchehaveanonspecializedapex,thatlookslikeaslenderradishinitsoutline. 9)Thelabrum externum.-diomedeaandphoebastriahave weak,shoulder-liketuberculum labriexternionthelabrum externum,andtheareabetweenthebilaterallabrum externum iswide. Thalasarchehasstraightlabrum externum andthetriangular areaisnarow.thebaseofpilacarinaeisthininthalasarche. 10)Thelabrum internum.-diomedeaandphoebastriahave asmalarticularsurfaceforthecoracoidonthelabrum internum. Thalasarchehasalateralywideone. Figure2.Themeasurementsandthedistinctionpointsonthedorsal surfaceoftheskulofalbatrosses. Figure4.Themeasurementsandthedistinctionpointsonthesternum ofalbatrosses. Figure3.Themeasurementsandthedistinctionpointsonthelateral andventralsurfacesoftheskulandmandibleofalbatrosses. Sternum (Figure4;Plate3) Threepointshavebeenrecognized. Coracoideum (Figure5;Plates10,11) Fivepointshavebeenrecognized. 11)Theimpresioligamentiacrocoracohumeralis.-Diomedea andphoebastriahaveslightimpresioligamentiacrocoracohumeralis.inthalasarche,thisimpresionisclearlydepresed. ThemarkedimpresionofthisligamentisregardedastheplesiomorphicfeatureinDiomedeidaebyMayrandSmith(2012). 12)Theangleofstandingextremitasomaliscoracoideitothe planeofcorpuscoracoidei,themedialview.- Theangleis relativelysteepinphoebastria. DiomedeaandThalasarche haveagentleslopeofstandingextremitasomaliscoracoidei. 13)Thecorpuscoracoidei.-DiomedeaandPhoebastriahave widecorpuscoracoidei.itisobviousinphoebastriaespecialy. Thalasarchehasanarowcorpuscoracoidei,whichissomewhat similartotheconditionofnon-diomedeidprocelariformes. 14)Thefaciesarticularissternalis,itsmedio-dorsalpart.-The dorsallipischaracteristic.phoebastriauniquelyhasprojecting faciesarticularissternalis.thalasarcheuniquelyhaslateraly wide,platform-likefaciesarticularissternalis.diomedeashows theintermediateconditionbetweenthalasarcheandphoebastria. 15)Thefaciesarticularissternalis,thetotalprofile.- Albatrosescommonlyhavethefaciesarticularissternalisinwhich themainmedialareaandaremotesmaloneareisolatedlateraly.theseparatedconditionsarecharacteristictoeachgenera. InDiomedeaandPhoebastriathesmallateralportionisinsu-

7 Comparativeosteologyofalbatroses 41 lated.thalasarchehaslong,medialyextendingfaciesarticularissternalisonthedorsalsurfaceofthecoracoid,andthenthe distancebetweenthemainmedialareaandthelateralportionis close. Figure5.Themeasurementsandthedistinctionpointsonthecoracoid ofalbatrosses. Humerus (Figures6,7;Plates4,5,6,9) Eighteenpointshavebeenrecognized. 16)Theanglecreatedbythemarginofcristadeltopectoralis andthelongitudinaldirectionofcaputhumeri.-whentheflat surfaceofmargocaudalis-cristadeltopectoralisareaisplaced flattothefaceoftheexaminer,theanglecreatedbytheproximal margocaudalisandthemarginofcristadeltopectoralisofeach speciesare:diomedeaexulans,25.5 ;Phoebastriaalbatrus, 28.2 ;P.nigripes,26.0 ;andboththalasarchespp.,29.5. Theresultsarenotcritical,butwemaysay:Diomedeashowsa paralelingtendency;thalasarcheshowarelativelyhighangle, nearly30 ;andphoebastriaisinbetween.thispointmightbe usefultointerpretthephylogenyofsmalspeciesatleast,asp. nigripesandthalasarchespeciesshow obviouslydiferent angles. 17)Thecranio-caudalaspectofcaputhumeri.- Diomedea andphoebastriahavethecaputhumerihighlyprominent,and alsothevertexlocateshiftingventraly.thalasarcheshowsa lowandneutralshape. 18)Thedorso-ventralaspectofcaputhumeri.- Diomedea andphoebastriashow theprofilebeingaperfectcircle,or slightlythinnercranio-caudaly.itislowandrelativelythicker cranio-caudalyinthalasarche. 19)Thetuberculum dorsale. - DiomedeaandPhoebastria havethetuberculum dorsaleofwhichthefacetfortheinsertion ofm.supuracoracoideusfaceproximo-cranialy. Thefacetin Thalasarchefacestotalycranial. 20)Thedistalmarginoftuberculum dorsale.-indiomedea andphoebastria,thedistalmarginoftuberculum dorsaleis smoothandlip-like.thalasarchehasasharp,crestedmargin there. 21)Theproximalterminatingareaofcristadeltopectoralisin caudalsurface,whereisequaltothedorso-distalbasalareaof tuberculum dorsale.- TheareaissunkeninDiomedeaand Phoebastria,andthenthecristadeltopectoralisisrelativelythinner. Thalasarchehasthikercristadeltopectoraliswithnosinking. 22)Theapexofcristadeltopectoralis.-InPhoebastria,the apexhooksandprojectsdorsodistalyandhangsoverthedistal partofthemarginofcristadeltopectoralis.itgoesdorsalyand thehookingisslightinthalasarcheanddiomedea. 23)Thecranio-caudalaspectofcristabicipitalis.-Diomedea andphoebastriahavethecristabicipitalisofwhichtheproximal regionisstraightandtheprofilecurvesstronglyatthedistaltermination.thalasarchehastheprofileofcristabicipitaliswhich swelsoutonthewholeandhasthevertexlocatedatthemiddle. ThispointisthereflectionofPoint27. 24)Thefacetfortheinsertionofm.subscapularis.-InDiomedeaandPhoebastria,thisfacetislocatedatthepositionbeing slightlycranialtotheproximalbaseofthetuberculum ventrale, andisnotvisibleinthecaudalsurfaceofthisbone.inthalassarche,itisatthepositionrelativelycaudal,andtheimpresion isvisibleinthecaudalsurface. 25)Thefacetfortheinsertionofplicaesynovialescoracoidea etscapularis,itspositionincontrasttothefacetfortheinsertion oflig.acrocoracohumerale. - Theformerfacetislocated proximo-dorsalytothelaterfacetindiomedeaandphoebastria. Thalasarchehastheformerfacetlocatedjustproximaltothe laterfacet,andthenthetwofacetsform an8-shapedarangement. 26)Thelinearimpresionofarticularcapsuleofcaputhumeri, onthecranialsurface.-thereisapartcurvinginproximaly indiomedeaandphoebastria.itisstraightandthelinedepreses toform agrooveinthalasarche. 27)Thecranialbulgeofcristabicipitalis,itscranialview.- Diomedea and Phoebastria have welexpanded teardropshapedcranialbulgeofcristabicipitalis. Itswelsoutonthe wholeinthalasarchebutthedegreeisnotstrongerthantheexpandedsituationseenindiomedeaorphoebastria. 28)Theinsertionofm.pectoralis.-InDiomedeaandPhoebastria,thefleshyinsertionislimitedonlyonthedistalregion ofcristadeltopectoralis.thalasarchehasafleshyinsertionto thelevelmoreproximaltotheapexofcristadeltopectoralis. 29)Theshapeofproc.supracondylarisdorsalis.-Diomedea andphoebastriahaveprojectingproc.supracondylarisdorsalis, projectsverticalyfrom theshaft,orratherproximalydirected. Theproc.supracondylarisdorsalisinThalasarcheislowand dulandisdirectedratherdistaly. 30)Thefacetbeingontheproximalbaseofproc.supracondylarisdorsalis.- DiomedeaandPhoebastriahavethisfaceton thecranialsurfaceofproc.supracondylarisdorsalis,andthen theprofileoftheprocesisnotafectedbythisfacet.thalassarchehasthisfacetonthebasalregionoftheproximalmargin ofproc.supracondylarisdorsalis,andthentheprofileofthe procesisnochedatthisregion. 31)Thefosaolecrani.-InDiomedeaandPhoebastria,the

8 42 MATSUOKAHiroshigeandHASEGAWA Yoshikazu Figure 6.The measurements ofthe humerus and the distinction pointsonthecaudalanddorsalsurfacesoftheprocimalhumerus. caudalmarginoffosaolecranicurvesinproximalyandshows agentlesigmoidalcurve. InThalasarche,becauseofthe weaklyswolencaudo-distalcornerofthisbone,thefosaolecranicontinuesstraightdorsaly. 32)Thecoupledtuberculaonentepicondyle.-Diomedeaand Phoebastriahavetwotinytuberculaontheentepicondyleand thedistancebetweenthetwotuberculaisclose.thalasarche hasaprominentdistaltuberculum,andthetwotuberculaareindependentofeachother. 33)Thedepresioninbetweenthefosam.brachialisandcondylusdorsalishumeri.- Thedepresionisclearanddeep, deepertothecenterinphoebastria.shalowinthalasarche. TheconditioninDiomedeaseemssimilartoThalasarche,but, becauseofthelargesive,thefeatureisdul. Ulna (Figures8,9;Plates8,9,10) Tenpointshavebeenrecognized. 34)Theproximalend,especialyinthecranialview.-Itdoes notexpandindiomedeaandphoebastria.thalasarchehasa relativelylargeproximalend,whichexpandswidely. 35)The proximalextention ofmargo caudalis. - Itis straightlycontinuousfrom theolecranoninphoebastria. In Thalasarche,thecrestiscrookedatthepointjustdistaltothe olecranon.theconditionindiomedeaissimilartothalasarche,buthastwocrookedpoints. 36)Theshaft.-TheshaftinDiomedeaandPhoebastriadoes notchangeitssizeincontrasttotheproximalend.theshaftin Thalasarcheisthinandlooksdelicate. 37)Thecrusrunninginthecranialsurfaceoftheproximalend beingbetweenthecraniallipofcotylaventralisandproximal terminationofthelineaintermuscularis.-inphoebastria,the crusiswel-definedandbearsadorsalyrunningridgeonit. TheridgeissharpinP.albatrusbutslightlyindistinctinP. nigripes.thecrusisdulinthalasarcheanddiomedean,and doesnotbeararidgeonit. 38)ThedepresionwaledbythecrusofPoint37andthefacies articularisradialis.-inphoebastria,itdepresesdeeplyasa whole,likeacookingpan. DiomedeaandThalasarchehave thedepresionthatdeepenstothecenter,likethebotom ofa bowl. 39)Thesmalridgewhichcontinuestothefaciesarticularis radialis.-itissharpinphoebastria.indiomedeaandthalassarche,theridgeiswideanddul. 40)Theatachmentoflig.colateraleventrale.-ItiscraniodorsalywideinDiomedeaandPhoebastria.Thalasarchehas Figure7.Thedistinctionpointsonthecranialsurfacesoftheprocimalndandthedistalendofhumerus. Figure8.Themeasurementsoftheulnaand thedistinction points onthecaudalandcranialsurfacesoftheprocimalulna.

9 Comparativeosteologyofalbatroses 43 anarowandlongareaofthisatachment. 41)Theimpresiom.brachialis.-InDiomedeaandPhoebastria,itdeepensproximaly.Thalasarchehasshalowlydeppres onthewhole. 42)Thetuberculum carpale. Phoebastriahasapointingprojection.ThetipisroundinDiomedeaandThalasarche. 43)Theprojectingdirectionoftuberculum carpale,measured bytheanglecreatedbythedirectionofthetuberculum carpale andthelinedirectedbythemarginofcondylusdorsalisulnae whenitsdorsocaudalsurfaceisplacedhorizontaly;measuredin distalview.-phoebastriauniquelyhadarelativelyhighangle, 50.Itisrelativelylow-angledinDiomedeaandThalasarche, about40. Pelvis (Figure10;Plates12,13) Onlyonepointhasbeenrecognized. 47)Thenumberofthoracicelements(theonesbearingmasive proc.transversus)inanteriorsynsacrum.-theresultsofcounting are:p.albatrus,5;thalasarchespecies,both,6;d.exulans andp.nigripeshavesmalproc.transversusinthe6thvertebra, andtheconditionshouldbecountedas5.5.wemaysaythat Thalasarchehasmasiveproc.transversusin6anteriorvertebraeofsynsacrum,whereasPhoebastriaandDiomedeahave5, ortendingtobe5,anteriorvertebraewhichhavemasiveproc. transversus.fartherinvestigationisawaited. Figure10.Themeasurementsandthedistinctionpointsonthepelvis. Figure9.Themeasurementsandthedistinctionpointsontheradius (left)and carpometacarpus(right),and thedistinctionpointsonthe diatalulna(median). Femur (Figure11;Plate14) Fourpointshavebeenrecognized. 48)Thecristatrochanteris.-InDiomedeaandPhoebastria,it Radius (Figure9;Plate8) Twopointshavebeenrecognized.Bothareinthedistalend. 44)Thecaudalmarginofdistalend.-Itexpandsdrasticalyat theendinphoebastria.diomedeaandthalasarche,especialy Diomedea,haveagentleexpansionstartingfrom theslightly proximallevel. 45)Thecranialborderofsulcustendineus.-ItisclearinDiomedeaandPhoebastria.ItisweakinThalasarche,because oftheswolencranialregionofthedistalend. Carpometacarpus (Figure9;Plate10) Notwithstandingitscomplexmorphology,fewcharacteristics wererecognizedtobeintergenetic. Onlyonepointhasbeen recognized. 46)Theosmetacarpalemajus.-InDiomedeaandPhoebastria, theshaftisstraightandthethicknesdoesnotchangethroughout.inthalasarche,itistaperingoftowardthedistalend. Figure11.Themeasurementsandthedistinctionpointsonthefemur.

10 44 MATSUOKAHiroshigeandHASEGAWA Yoshikazu isstraightinanteriorview,anditsmedialmargincontinuesto thelineaintermusculariscranialis. Thalasarchehasmedialy swolencristatrochanteris,andthentheproximallineaintermusculariscranialiscariesintothedistalcristatrochanteris. 49)Theimpresionesobturatoriae.-ItisflatinDiomedeaand Phoebastria.Thalasarchehasdepresedimpresionesobturatoriae. 50)Thecondyluslateralis.-DiomedeaandPhoebastriahave clearlyridgedcristatibiofibularis. Thalasarchehasteardropshapedcondyluslateralisofwhichcristatibiofibularisisfaded. 61)Thebotom oftrochleacartilaginistibialis.- Diomedea andphoebastriahaveaweakbutobviousridgeinthemedian areaoftrochlea.thalasarchehasanalmostflatmedianbotom. 62)Thelateralmarginoftrochleacartilaginistibialis.-Itis sharpandthinindiomedeaandphoebastria.thalasarchehas ashalowtrochleaandthemarginismasive. 51)Thedepresionbeingjustproximaltothetrochleafibularis intheposteriorsurfaceofdistalend.-indiomedeaandphoebastria,thedepresionisshalow.alsointhesegenera,thedepresionisseparatedfrom fosapopliteabythecruswhichisat thepositionjustproximaltothecondyluslateralis.thalasarche hasarelativelydeepdepresion,andthecrusseparatingthis from fosapopliteaisweakandtwodepresionsarecontinuous. Tibiotarsus (Figure12;Plates14,15) Fourpointshavebeenrecognized.Mostofthem areinthe distalend,andaremostly(points57-62)seeninthedistalend view. 52)Thecristafibularis.-ItisshortinDiomedeaandPhoebastria.Thedistalterminationisatthepositionoftheforamen nutriens.inthalasarche,itislong,reachingmuchdistaltothe foramennutriens. 53)Thepointedproximalendofcristacnemialiscranialis.- InDiomedeaandPhoebastria,thepointedendhasanotchat theposteriorsurfaceofthetip,andthentheprofileisdentedin thelateralview.thalasarchedoesnothavethisnotchandthe lateralviewisround. 54)Theroughenedsurfaceofthemedialsurfaceofcristacnemialiscranialis.-Uniquely,Diomedeahasawideroughened surfaceasdistalasreachingtheproximalshaft.itisnotstrong intheothertwogenera. 55)Thecristacnemialislateralis.- Ontheanteriorsurface, DiomedeaandPhoebastriahaveagrooveatthelateralmarginal position.thalasarchedoesnothavesuchgroove. 56)Thetriangularteracejustproximaltothecondyluslateralis ontheanteriorsurface.- InDiomedeaandPhoebastria,the teraceisdevelopedandobservableinthedistalendview.thalasarchehasanundevelopedflatone. 57)Thegeneralviewofthearticularsurfaceofdistalend.- InDiomedeaandPhoebastria,itislateralynarow.Thalasarchehasawidearticularsurface,thatmeansthedistalendexpandslateralyfrom theshaft. 58)Thecondyluslateralis.- InDiomedeaandPhoebastria, themedialsideissunken,andhasamedianridge.thalasarche hasswolencondyluslateralisanddoesnothavesucharidgeon it. 59)Thecondylusmedialis.-DiomedeaandPhoebastriahave longandstraightmedialborder.inthalasarche,themedial borderbendsatthemiddle. 60)Theanglecreatedbythedirectionofthebotom ofsulcus intercondylarisandthedirectionoftheposteriorsurfaceofdistal end,observedandmeasuredinthedistalendview.-diomedeaandphoebastriaarerelativelyhigh-angled,whereasitis relativelylow-angledinthalasarche. Figure12. Themeasurementsandthedistinctionpointsonthetibiotarsus. Tarsometatarsus (Figures13,14;Plates15,16) Elevenpointshavebeenrecognized. 63)Thegeneralconditionincraniodorsalaspect.-InDiomedeaandPhoebastria,theproximalanddistalendsdonotexpanddrasticalyfrom theshaft.thalasarchehasanexpanded profileintwoends. ThispointdistinguishingThalasarche from DiomedeaandPhoebastriaisalsoreportedbyOlsonand Rasmusen(2001). 64)Theshaft.-InDiomedeaandPhoebastria,theshaftisanteroposteriorlythick,andthenthetransversalsapectresemblesa square.thalasarchehasaslightlythinshaft,anditstransversal sapectresemblesarectanglelateralylong. 65)Thecotylaelateralisetmedialis.-Theyarecompactand deepindiomedeaandphoebastria.thalasarchehaswideand shalowones. 66)Theeminentiaintercotylaris.-Itishighlyprominentin DiomedeaandPhoebastria.Thalasarchehasloweminentiaintercotylaris,anditisaboutthesameheightasthepeakofthe medialmargineofcotylamedialis. 67)Thefosainfracotylarisdorsalis.-InDiomedeaandPhoebastria,theproximalslopeofdepresiondeepensgradualy.In Thalasarche,itdeepensdramaticalyfrom theproximalmargin, likeacookingpan. 68)Thepositionofproximalforamina.- Thedistancebetweentheproximalmarginoffosainfracotylarisdorsalisand theproximalforaminaisprorongedindiomedeaandphoebas-

11 Comparativeosteologyofalbatroses 45 tria.itisshortinthalasarche. 69)Theimpresioretinaculiextensori.-ItisobviousinDiomedeaandPhoebastria,whereasfadedinThalasarche. 70)Themedialportionofhypotarsus.- InDiomedeaand Phoebastria,thelineformedbythecristamedialishypotarsi andthecristamedianoplantarisrunsalongthemedialposition attheverymarginoftheposteriorshaft.thalasarchehasthe linerelativelymedian,andthenthemedialsurfaceoftheshaft isobservableintheposteriorview. 71)Thecristamedianoplantaris.-Inthemedialviewofthe hypotarsus,theconditionofthecristamedianoplantarisischaracteristic. InDiomedeaandPhoebastria,thecristarisesata relativelyhighangle(27 )from theposteriorshaft. Alsoin thesegenerabothcristamedianoplantarisandcristamedialishypotarsihaveastraightmargininmedialview,andthesetwo linescontactattheangle thalasarchehasthecrista Figure 13.The measurements and the distinction points on the tarsometatarsus. medianoplantariswhichrisesgradualywithlow angle(10 ) from theshaft. Thecristamedianoplantarisandcristamedialis hypotarsiform aroundmedialprofileandthesetwoportions lookcontinuousataglance. 72)Theconditionofcristaintermediahypotarsi.-Thecrista isweaklydevelopedindiomedeaandphoebastria,andthenthe sulcushypotarsimedialnexttothecristaintermediahypotarsiis widelyopen.inthalasarche,thecristadevelopsandthemedialsulcusisoverhangedbythemedialmarginofthiscrista. 73)Thetrochleametatarsi I.-Intheanteriorview,themedialandlateralmarginsoftrochleaarenearlyparalelinDiomedeaandPhoebastria.Thalasarchehasthetrochleadistaly widened,andthentheviewofthetrochleafrom thedistalendis barel-shaped. Concludingremarks: osteology-basedphylogeneticanalysisof Diomedea genera Recently,theprogresofmolecularphylogenyisremarkable andprovidesgoodopportunitiestoreconsidermorphological clasification.therecentmovementonthetaxonomyofalbatrosesisitsgoodexample.theclasificationthatlumpedalbatrosesinto Diomedea andphoebetriausedtobewidely accepted,butisoverturnedand,farfrom that, Diomedea was revealedasaparaphyleticgroup(nunnetal.,1996). The73pointsdescribedinthisstudyisconcludedasthecombinationof:60pointssharedbyDiomedeaandPhoebastria,9 pointssharedbydiomedeaandthalasarche,1pointsharedby PhoebastriaandThalasarche,and3pointsofDiomedeashow theintermediatefeaturesbetweenphoebastriaandthalasarche. Basedonthisresult,DiomedeaandPhoebastriashowinghigh commonalityandmustbeinaclade,whereasthalasarche shouldbeseparatedasthesistergroupofthediomedea-phoebastriaclade. WehaveakeyfosilTydeaseptentrionalis,astem grouprepresentativeofdiomedeidaefrom theearlyoligocene(30 31 Ma)ofBelgium reportedbymayrandsmith(2012).consideringthefeaturesborneintydeaseptentrionalis,suchasthe Thalasarche-likeconditionoftheprocesusacrocoracoideusof Figure14.Thedistinctionpointsonthetarsometatarsus. Figure15.Theosteology-basedphylogenyofalbatrosses.

12 46 MATSUOKAHiroshigeandHASEGAWA Yoshikazu coracoidandthemarkedimpresioligamentiacrocoracohumeraliswhichisplesiomorphicindiomedeidae(mayrand Smith,2012),weareguidedtoconcludethat:Thalasarcheis inthemostprimitivestateamong Diomedea generaandthe cladeincludingdiomedeaandphoebastriaderivedfrom the cladeofthalasarche.itisenigmaticthat9pointsareshared inthelargestdiomedeaandthesmalestthalasarcheiftheosteologyiscontroledbythefunction.itmightberegardedthat DiomedeaisinarelativelyprimitivestateintheDiomedea- PhoebastriacladewhereasPhoebastriaisthemostadvanced amongthree Diomedea genera. Ifwetreatthe73pointsequivalently,thephylogeneticrelationshipofalbatrosesisasinFigure15.Thisresultmatches weltothecurentview(nunnetal.,1996)ofthephylogenyof albatroses.phoebetria,thoughthisstudydidnotexaminethe osteologyindetail,becauseofitsimpresivelyshortsternum, seemstobemuchmorederivedthan Diomedea andderived from it.theancestorofphoebetriamustbethalasarche.the nextsubjectwilbetheosteologyofphoebetria,whichisexpectedtobearthecombinationofthalasarche-likeprimitive conditionanduniquelyderivedfeatures. Acknowledgements Weexpresoursinceregratitudetoalpersonswhohelpedto colectosteologicalspecimens.wethankmr.junyawatanabe ofthegraduateschoolofscience,kyoto University who kindlyhelpedtoobtainrarepapersandspecimeninformation. References Alexander,W.B.,Fleming,C.A.,Fala,R.A.,Kuroda,N.-H.,Jouanin,C., Rowan,M.K.,Murphy,R.C.,Serventy,D.L.,Salomonsen,F.,Ticknel,W.L.N.,Voous,K.H.,Warham,J.,Watson,G.E.,Winterbotom, J.M.,Bourne,W.R.P.(1965):Corespondence:Thefamiliesand generaofthepetrelsandtheirnames.ibis,107(3): Baumel,J.J.andWitmer,L.M.(1993):Osteologia.InBaumel,J.J.,King, A.S.,Breazile,J.E.,Evans,H.E.andVandenBerge,J.C.(eds.) HandbookofAvianAnatomy:NominaAnatomicaAvium,PublicationsoftheNutalOrnithologicalClub,(23): Coues,E.(1866):CriticalreviewoftheFamilyProcelaridae,partV,embracingtheDiomedeinaeandtheHalodrominae.Proceedingsofthe AcademyofNaturalSciencesofPhiladelphia,18: Dénes,F.V.andSilveira,L.F.(2007):Cranialosteologyandtaxonomyof albatrosesofgenusdimedealinneaus,1758andthalasarchereichenbach,1853(procelariformes:diomeidae).papéisavulsosdezoologia(sãopaulo),47(3): Howard,H.(1929):TheAvifaunaoftheEmeryvileShelmound.UniversityofCaliforniaPublicationsinZoology,32(2): Matsuoka,H.,Kawakami,T.andKoike,H.(2009):Onasmalalbatrosoccuredfrom themiddlemioceneaokiformationofazumino,nagano, Japan.ResearchReportoftheShinshushinmachiFosilMuseum,(13): 1-6. Mayr,G.andSmith,T.(2012):Afosilalbatrosfrom theearlyoligocene ofthenorthseabasin.theauk,129(1): Nunn,G.B.,Cooper,J.,Jouventin,P.,Robertson,C.J.R.andRobertson, G.G.(1996):Evolutionaryrelationshipsamongextantalbatroses (Procelariformes:Diomedeidae)establishedfrom completecytochrome-b genesequences.theauk,113(4): Olson,S.L.andRasmusen,P.C.(2001):MioceneandPliocenebirdsfrom theleecreekmine,northcarolina.smithsoniancontributionstopaleobiology,(90): Only,D.andScofield,P.(2007):Albatroses,petrels,& shearwatersofthe world.princetonfieldguides:princetonuniv.pres,240pp. VondenDriesch,A.(1976):Aguidetothemeasurementofanimalbones from archaeologicalsites.peabodymuseum Buletin,1,i-iv PeabodyMuseum ofarchaeologyandethnology,harvarduniversity.

13 Comparativeosteologyofalbatroses 47 アホウドリ類 3 属 Diomedea Phoebastria Thalasarche の比較骨学 松岡廣繁 1 2 長谷川善和 1 京都大学大学院理学研究科地球惑星科学専攻地質学鉱物学教室 : 京都市左京区北白川追分町 2 群馬県立自然史博物館 : 群馬県富岡市上黒岩 要旨 : 現在もっとも受け入れられている分類では, アホウドリ科の現生属にはDiomedea Phoebastria Thalasar- che Phoebetria の4 属が存在する. これらのうちPhoebetria を除いた3 属は, 最近まで形態的に広義のDiomedea( ここでは Diomedea と表記する ) に纏められていた. 骨学的にも,Phoebetria は他の3 属に対して特異で, 古生物学の分野でも多くの化石が Diomedea と同定されてきた. Diomedea が分割されるべきことが明らかになった今日でも,Diomedea Phoebastria Thalasarche の3 属が骨学的に判別可能かどうかの検討はほとんどなされておらず, アホウドリ類の進化史復元に大きな問題となっている. そこで本研究はDiomedeaexulans( ワタリアホウドリ ),Phoebastriaalbatrus( アホウドリ ),Phoebastrianigripes( クロアシアホウドリ ),Thalasarchemelanophris( マユグロアホウドリ ),Thalasarchechlororhynchos( ニシキバナアホウドリ ) の骨格標本を用い, この3 属が骨学的に判別可能であるかを検討した. 結果, 主要骨格要素に合計 73 ヶ所に判別点を認めた. その分布には要素や部位によって多寡があるが, この3 属は骨学的に十分判別可能であることを示している. 判別点 73 のうち60 ヶ所でDio- medea とPhoebastria は共通した特徴を有し, 両者の強い近縁性を示している. 一方それらが成すクラスターは Thalasarche とは明瞭に区別される. 中でも,Phoebastria とThalasarche とで共通するのは1ヶ所しかない. 化石属の基幹的アホウドリ類の形態を考慮すると,3 属中ではThalasarche が原始形質を示し,Diomedea とPhoebastria からなるクレードがこれから派生したものと考えられる.Diomedea とThalasarche とに共通し,Phoebastria が異なった特徴を示す点が9か所あるが,Diomedea は超大型種でありThalasarche はアホウドリ類の中では最小で, これらの類似点は機能上の収斂とは考えがたく, 奇妙なことである. ここでは,Diomedea とPhoebastria からなる派生的クレードの中ではDiomedea にはいくらかの原始形質が遺存する一方,Phoebastria が最も派生的だと考えた. 本研究を基礎として,Phoebetria を含めてアホウドリ科内の骨学的研究を進めるならば, 化石種のより正しい同定が可能となり, 進化系統の復原に重要な基礎情報となるであろう.

14 48 MATSUOKAHiroshigeandHASEGAWA Yoshikazu Platecaptions Plate1:Comparisonofthelateralviewoftheskulsofalbatroses.From thetoptothebotom,theyare:thalasarchechlororhynchos, Phoebastriaalbatrus(thesetwohavethemandiblesinarticulation)andPhoebastrianigripes,DiomedeaexulansandThalasarche melanophris. Plate2:Comparisonofthedorsalandventralsurfacesoftheskuls,betweenPhoebastria,DiomedeaandThalasarche. Plate3:ComparisonoftheventralandlateralviewsofthesternumsofPhoebastria,DiomedeaandThalasarchealbatroses. Plate4:ComparisonofthehumerusofDiomedeaexulansandPhoebastriaalbatrus.Thecaudalandcranialviewsofrighthumeri. Plate5:ComparisonofthehumerusofPhoebastrianigripes,Diomedeaexulans,ThalasarchemelanophrisandT.chlororhynchos, togetherwith Macronectesgiganteus(Procelaridae).Thecaudalandcranialviewsofrighthumeri. Plate6:Comparisonofthedorsalandventralsurfacesoftheproximalhumeri,betweenPhoebastria,DiomedeaandThalasarche. From thetoptothebotom,thethreerowsare:cranial,caudal,anddorsalsurfacesoftherighthumeri. Plate7:Comparisonoftheulnaeofalbatroses.From thelefttoright,theyare:diomedeaexulans,phoebastriaalbatrus,p.nigripes, ThalasarchemelanophrisandT.chlororhynchos. Plate8:Comparisonofthedorsalsurfaceoftheulnaeanddorsalandcranialsurfacesoftheradiusofalbatroses.From thelefttoright, theyare:diomedeaexulans,phoebastriaalbatrus,p.nigripes,thalasarchemelanophrisandt.chlororhynchos. Plate9:Comparisonofthedistalendofthehumerusandproximalanddistalendsofulna,betweenPhoebastria,DiomedeaandThalasarche. From thetoptothebotom,thethreerowsare:thecranialandventralviewsofthedistalendsofhumerus,caudalandcranialviews ofproximalendsofulna,anddorsalviewsofdistalulnae.therightbotom areaoftheplateisthedistalendviewsofrightulna. Diomedeaexulans,PhoebastrianigripesandThalasarchemelanophrisareshownasthegeneticrepresentatives.Alscalebars are5cm long,andeachbarscorespondtothetransversalrows. Plate10:ComparisonofthecoracoidandcarpometacarpusbetweenPhoebastria,DiomedeaandThalasarche.Theleftandrightfiguresof coracoidsaretheventralanddorsalsurfaces.thetopandbotom figuresofcarpometacarpiaretheventralanddorsalsurfaces. Plate11:ComparisonofthecoracoidinthreeviewsbetweenPhoebastria,DiomedeaandThalasarche.Themediallateral,andbasalviews from thetoptothebotom.thespeciesare:diomedeaexulans,phoebastrianigripes,thalasarchemelanophrisandt.chlororhynchos.alscalebarsare5cm long,andeachbarscorespondtothetransversalrows. Plate13:ComparisonofthepelvisbetweenPhoebastria,DiomedeaandThalasarche.Diomedeaexulans,Phoebastriaalbatrus,P.nigripes, ThalasarchemelanophrisandT.chlororhynchos.Ventralviews. Plate12:ComparisonofthepelvisbetweenPhoebastria,DiomedeaandThalasarche.Dorsalviews.Theyare:Diomedeaexulans,Phoebastriaalbatrus,P.nigripes,ThalasarchemelanophrisandT.chlororhynchos. Plate14:RightfemursandrighttibiotarsiofDiomedeaexulans,Phoebastriaalbatrus,P.nigripes,ThalasarchemelanophrisandT.chlororhynchos,from thelefttoright.femursareinanteriorandposteriorviews,andtibiotarsiareinmedialandposteriorviews. Plate15:RighttibiotarsiandrighttarsometatarsiofDiomedeaexulans,Phoebastriaalbatrus,P.nigripes,Thalasarchemelanophrisand T.chlororhynchos,from thelefttoright. Tibiotarsiareinanterioranddistalendviews,andtarsometatarsiareinanterior (dorsal),posterior(basal),andviewsfrom thetoptobotom. Plate16:ThecloseupfiguresofrighttarsometatarsiofDiomedeaexulans,Phoebastrianigripes,ThalasarchemelanophrisandT.chlororhynchos,from thelefttoright.from thetoptobotom,figuresofeachspeciesshowtheproximalarticularsurface,medial,anterior,and posteriorviewsofproximalend,theanteriorviewofthedistalend,andthedistalarticularsurfaceofrighttarsometatarsus.

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