New hyaenodonta (Mammalia) from the middle Eocene of Myanmar

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New hyaenodonta (Mammalia) from the middle Eocene of Myanmar

Louis de Bonis, Floréal Solé, Yaowalak Chaimanee, Aung Naing Soe, Chit Sein, Vincent Lazzari, Olivier Chavasseau, Jean-Jacques Jaeger

To cite this version:

Louis de Bonis, Floréal Solé, Yaowalak Chaimanee, Aung Naing Soe, Chit Sein, et al.. New hyaen-

odonta (Mammalia) from the middle Eocene of Myanmar. Comptes Rendus Palevol, Elsevier, 2018,

17 (6), pp.357-365. �10.1016/j.crpv.2017.12.003�. �hal-02100308�

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ContentslistsavailableatScienceDirect

Comptes Rendus Palevol

www . s c ie n c e d i r e c t . c o m

General Paleontology, Systematics, and Evolution

New hyaenodonta (Mammalia) from the middle Eocene of Myanmar

Nouveaux hyaenodontes (Mammalia) de l’Éocène moyen de Birmanie Louis de Bonis

^a,∗

, Floreal Solé

^b

, Yaowalak Chaimanee

^a

, Aung Naing Soe

^c

, Chit Sein

^d

, Vincent Lazzari

^a

, Olivier Chavasseau

^a

, Jean-Jacques Jaeger

^a

aIPHEP:Institutdepaléoprimatologieetdepaléontologiehumaine,évolutionetpaléoenvironnements,UMRCNRS7262,Universitéde Poitiers,6,rueMichel-Brunet,86073Poitierscedex9,France

bRoyalBelgianInstituteofNaturalSciences(RBINS),OperationalDirectorateEarthandHistoryofLife,29,rueVautier,1000Bruxelles, Belgium

cDepartmentofHigherEducationMinistryofEducation,Naypyitaw,Myanmar

dDepartmentofGeology,WestYangonUniversity,11393Yangon,Myanmar

a rt i c l e i n f o

Articlehistory:

Received13November2017

Acceptedafterrevision16December2017 Availableonline27February2018 HandledbyLorenzoRook

Keywords:

Hyaenodonta Hyainailouridae Hyaenodontidae PondaungFormation Novaspecies

a b s t r a c t

ThemiddleEocenePondaungFormationinMyanmarhasyieldedarichmammalianfauna includingseveralPrimatetaxa.HyaenodontaareknownbythegeneraKyawdawia,Yarshea, Orienspterodon,andtwootherindeterminatetaxa.WedescribeherenewmaterialofKyaw- dawia,includingsomemorphologicaldetails,anewspeciesofthehypercarnivorousgenus Propterodonandanindeterminatespecies,differentfromthosedescribedearlierinMyan- mar,andcharacterizedbyareductionofm3andwouldbelongtoathirdlineagewiththe sameevolutionarytrendasGalecyonandtheLimnocyoninae.Thehyainailourines(Orien- spterodon)andhyaenodontines(Propterodon)arerecordedfortheﬁrsttimeinSoutheast AsiaandthesesubfamiliesappearedinquasithesametimeinEuropeillustratingprobably aprofoundchangeinthecarnivorousfaunaamongLaurasia.

Motsclés: Hyaenodonta Hyainailouridae Hyaenodontidae FormationdePondaung Novaspecies

r é s um é

Laformationdel’ÉocènemoyendePondaung,enMyanmar,alivréunerichefaunemam- malienne,danslaquelleonasignaléplusieurstaxonsdePrimates.Parmilesautresordres demammifères,celuidesHyaenodontaétaitconnujusqu’àprésentparlesgenresKyaw- dawia,Yarshea,Orienspterodonetdeuxautrestaxonsindéterminés.Nousdécrivonsdanscet articledunouveaumatérieldeKyawdawia,quiapportedesprécisionssurcertainsdétails morphologiques,unenouvelleespècedugenrehypercarnivorePropterodonainsiqu’une formeindéterminée,quidiffèredetouteslesespècesdécritesàcejourenBirmanie.Ellese

∗ Correspondingauthor.

E-mailaddress:louis.debonis@univ-poitiers.fr(L.deBonis).

https://doi.org/10.1016/j.crpv.2017.12.003

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358 L.deBonisetal./C.R.Palevol17(2018)357–365

caractérise,enparticulier,parlaréductiondem3,etpeutreprésenterunetroisièmelignée montrantlamêmetendanceévolutivequelesLimnocyoninaeetGalecyon.Leshyainailour- inés(Orienspterodon)etleshyaenodontinés(Propterodon)sontlesplusanciensconnus dansleSud-Estasiatique.Cessous-famillesapparaissentquasimentàlamêmeépoqueen Europe,etlaﬁndel’Éocènemoyenpourraitcorrespondreàunchangementmajeurdela faunedecarnassiersenEurasie.

1. Introduction

ThemiddleEocenePondaungFormation,exposedinthe northwestern partof Central Myanmar, is mainly com- posed of ﬂuviatile sediments, and has produced a rich vertebratefauna.SincetheﬁrstfossilsreportedbyPilgrim and Cotter (1916), about 50 mammalian species have beendiscoveredsuchasartiodactyls(Ducrocqetal.,2000;

Holroydand Ciochon,1995; Métais,2006;Métaisetal., 2000;Pilgrim,1928;Tsubamotoetal.,2003,2011,2012, 2013),perissodactyls(Colbert,1938;Holroydetal.,2006;

Métaisetal.,2006;Rémyetal.,2005;Tsubamotoetal., 2003,2005),rodents(Dawsonetal.,2003;Marivauxetal., 2005), and primates (Ba Mawet al.,1979; Beard etal., 2005,2007,2009;Chaimaneeetal.,2000,2012;Ciochon, 1985;Colbert,1938;Geboetal.,2002;Gunneletal.,2002;

Jaegeretal.,1998,1999;Marivauxetal.,2008a,2008b;

Shigeharaetal.,2002;Takaietal.,2001).Theageofthe PondaungFormationhasbeenestimatedtobelatemid- dleEocene(ca.*37Ma)bymagnetostratigraphy(Benammi et al.,2002)and ﬁssion track dating (Tsubamotoet al., 2002).However,recent radiometricanalyses(U–Pbage) onzirconsobtainedfromatuffacaceousbedinPondaung Formationindicateanagerangebetween40.22–40.31Ma (KhinZawetal.,2014),whichisslightlyolderthanthat obtainedfromtheothermethods.Almost30fossiliferous localitieshavebeenrecognizedinthePondaungFormation anditsstratigraphicstudy,conductedbyAungNaingSoe etal.(2002),hasdemonstratedthatsedimentsthatyielded fossilmammalremainsweredepositedinthesameshort timeinterval andareissued fromtheupperpartof the PondaungFormation.Geochemical,sedimentologicaland paleoenvironmentaldataindicateatropical,humidenvi- ronmentunder strongmonsoon inﬂuences(Licht etal., 2013a,2013b,2014).MoststudiesonthePondaungfos- silmammalshavefocusedonanthracotheriidartiodactyls andprimatesbecausetheyarethemostabundanttaxathat havebeencollectedsincethebeginningofthetwentieth century.Herewereportnewdiscoveriesthatincreaseour understandingoftheHyaenodontaofthatformation.

The ﬁrst hyaenodonts recovered in Myanmar were brieﬂydescribed(EgiandTsubamoto,2000)fromspeci- menscomingfromthePondaungareaastwoindetermi- natespeciesinanoverallreviewofthefossilmammalian fauna of Myanmar. Few years later (Egi et al., 2004), one of these species was publishedas Yarshea cruenta onfragments of thesame individual (NMMP-KU 0045;

ﬁeldnumberBhn-31,rightmandibularfragmentwithm1;

NMMP-KU0046,rightm3trigonid;NMMP-KU0214,right m2andm3talonids,metastylarbladeandprotoconeofleft M1orM2,atoothrootfragment).Thematerialwascom- ingfromthe“UpperMember”ofthePondaungFormation,

easternsideofPondaungRange,centralMyanmarinthe Bahinbasin(Egietal.,2004).Latertheotherspecieswas alsodescribed(Egietal.,2005)asKyawdawialupina,with cranialandpost-cranialelementsassociatedwiththeholo- type.Thedentitionwasquitecompletebut,belongingto anoldindividual,theteethareworn.Inthesamearticle, afragmentofmandiblebearingp4talonidandm1coming fromthesameareaandlevelisﬁguredasProviverrinae indet.SmallerthanYarsheaandKyawdawia,thismandible differsalsobycharacterswhichseemtobemoreAfrican proviverrine-like.Otherremainswererecordedfromthe samePondaungFormation(Peignéetal.,2007).Someof them werereportedasKyawdawialupinabut aM3ﬁg- uredasHyaenodontidaesp.indet.istoolargetobelongto theotherknownPondaungspeciesatthattime.Thesame yearanothergenus,OrienspterodonEgi etal.,2007,was createdforverylargespecimensfromPondaungandthe ChinesespeciesPterodondahkoensisChowMinchen,1975 wasassignedtothisgenus.

Thenewmaterialwhichisdescribedinthepresentarti- cleconsistsinmandibularfragmentsandisolatedteeth.

Thesenewﬁndsbothincreasetheknowndiversityofthe hyaenodontfaunainPondaungandprovidenewmorpho- logicaldetailsforpreviouslydescribedtaxa.

2. Systematics

HyaenodontaVanValen,1967 HyainailouroideaPilgrim,1932 HyainailouridaePilgrim,1932 IndohyaenodontinaeSoléetal.,2013 KyawdawiaEgietal.,2005

KyawdawialupinaEgietal.,2005

Thisspeciesisrepresentedinthenewmaterialbyan isolatedp3,afragmentofmandiblewithp4–m2,aP4,2 uppermolarsandsomefragmentsofteeth.

2.1. Descriptionofthelowerteeth

Theisolatedp3(NMMP-PK4-5-12-10a)isidentiﬁedas a lowerone,butanupperonecannotbeexcluded; itis little worn,smallerthan p4(Table1),witha triangular almostsymmetricallateralshape.Thereisathinparacristid descendingfromtheapexoftheprotoconidtomeetasmall paraconidand,distally,abetterdevelopedtalonid.

Thedentary(NMMP-PK2-2-11-13)isbrokenoffatmid- height and we cannot estimate the depth (Fig. 1). The mandible would havebeen quiterobustbeing10.6mm breadthatthelevelofm1–m2(Fig.1A–C).Thep4ishigher thanm1(Table1),robustandwithoutanytraceofwear.

Thesurface ofenamel isslightly granular.Thecrown is

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Table1

Measurements(mm)ofthelowerteethofKyawdakialupina.

Tableau1

Mesures(mm)desdentsinférieuresdeKyawdakialupina.

p3 p4 m1 m2 m3 References

L w h L w h L TrL trh trw talw L trL trh trw talw L trL trh trw tlw

NMMP-PK2-11-2-2017 9.2 5.8 8.8

NMMP-PK2-02-11-2013 13.3 6.2 10.8 11.9 6.5 7.7 6 5.9 15.9 9.9 11.5 9.5 7.5

NM11Bhn2000 13.6 8.2 7.4 6 Peignéetal.,2007

NPL-12-2010 7.5 15 8.4 8.9 Peignéetal.,2007

PKg1051 14.2 8 7.7 7.7 Peignéetal.,2007

NMMP-TMC-2016 12.1 6.3 9.9 5.3 4.1

NMMP-KU42 5.2 14.26.312.3 17.6 9.6 8.6 7.5 18.4 10.3 9.1 7.2 Egietal.,2005

NMMP-KU1288 9.4 6.4 9.3 15.27 13.6 13.4 6.9 8.5 6.4 6.2 20.3 12.5 16.1 11 8.3 Egietal.,2005

NMMP-MGW0022 11 9.7 5.6 4.7 5 Egietal.,2005

L:length;w:width;h:height;TrL:trigonidlength;trh:trigonidheight;trw:trigonidwidth;talw:talonidwidth.

Fig.1. Kyawdawialupina(PK2-2-11-13).Fragmentofdentarywithp4–m2.A.Lingualview.B.Buccalview.C.Occlusalview(stereo).IsolatedP4.D.Lingual view.E.Buccalview.Scalebar=10mm.

Fig.1. Kyawdawialupina(PK2-2-11-13).Fragmentdemandibuleavecp4–m2.A.Vuelinguale.B.Vuebuccale.C.Vueocclusale(stéréo).P4isolée.D.Vue linguale.E.Vuebuccale.Échelle=10mm.

bucco-linguallyﬂattened,themesialhalfbeingnarrower thanthedistalonewithasharpparalophidrunningfrom thetoptothebaseofthecrown.Thereisanothersmaller crestdistallyfrommid-heighttothebase.Thereisawell- developedtalonid(3.3mmlength)withoutaclearcristid obliqua butwitha highand powerful hypoconidanda narrowelongatedlingualﬂatsurfacereplacingtheweak cingulidsurroundingthetooth.Them1,slightlyshorter thanp4andfarsmallerthanm2(Table1),isalmostcom- pleteexcept thedisto-lingualcorner ofthetalonid. The trigonidiscompletewithaswollenmetaconidsmallerthan theparaconidbutneverthelesswelldevelopedandbearing asmallverticalmesio-lingualridge.Therearewearfacets onthetopofthethreecuspidsofthetrigonidandwecan- notknowtheoriginalheightofthecuspids.Thewearfacet isroundedandhorizontalintheprotoconidwithappear- anceofthedentineinthemiddle,elongatedandslightly

buccallyinclinedwithtracesofdentineintheparaconid anditisovalandhorizontalinthemetaconidwithalso apitof dentine.Anotherwearfacetextendsin thedis- talsurfaceoftheprotoconidandmetaconid.Thetalonid isslightlynarrowerthanthetrigonid(talw/trw=98).The lingualhalfofthetalonidisbrokenoff.Thecristidobli- qua,whoseamesialpartismissing,isperpendiculartothe protoconidandjoinstheconicalhypoconid,awearfacet runningalongthecrestandthetopofthehypoconid.The ratiowidthoftrigonid/widthoftalonid(98.3)isslightly higherthanthose(77.3to96.8)ofpublishedm1ofK.lupina (Egietal.,2005;Peignéetal.,2007).Them2isverywell preserved.Thetrigonid,overlookedbytheprotoconid,is highwithoutsigniﬁcanttracesofwearinthetopofthecus- pidsexceptaverytinyone,concerningonlytheenamel,in theapexoftheprotoconid.LikeinspecimenNMMP-Pkg- 1051,theprotoconidheightsurpassesthetrigonidlength.

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Theparaconidisveryoblique,nearlyperpendiculartothe axisofthetoothrawandslightlyseparatedfromthemeta- conid.Thelatteriswelldevelopedbutsmallerandslightly lowerthantheformer.Alargeverticalshearingwearfacet withverticalstriationsextendsonthebuccalsurfaceofthe protoconidandpartlytheparaconid.Thereisnotaclear cristidobliquainthetalonidbutalargehypoconidelon- gatedwithaslightlyconvexbuccalfaceandalingualone gentlyslopingtothedeepandwidetalonidbasin.Theento- conid,separatedfromthemetaconidbyadeepnotch,isas highasthehypoconidbutthinner;itconstitutesa crest separatedfromthehypoconulidbyasmallnotch,thelat- terbeingseparatedfromthehypoconidbyalargerone.A moderatecingulidrunsalongthebuccalbaseofthetooth exceptatthelevelofthedisto-buccalpartoftheproto- conid.Thetalonidbreadthissmallerthanthetrigonidone andtheratio(79)isslightlysmallerthanthose(87.2–100) previouslypublished(Egietal.,2005;Peignéetal.,2007).

2.2. Upperteeth

P4(Fig.1C,D)isthreerootedbutarootisbrokenoff.

Itisfreshexceptasmallpitofwearinthetopofthemain cuspandasmallpartofthemesio-buccalcornerbroken off.Itsmeasurementsare:width=8.4mm,height=9.7mm.

Wecannottakethelength.Themaincuspistriangularin lateralview;distallyathinverticalcrestrunsdowntoan elongatedandtrenchanttalon.Inthedistalwall,thereis asmallhorse-shoeshapedcontactfacetforM1.Another smallermesialaccessorycuspispresent.Linguallyatrue protoconedoesexistasabasinlimitedbythecingulumin whichasmalltransversecrestextendsfromthemaincusp toasharpsmallcusp,dividingthebasinintwoparts.The heightofthecrownissimilartothelengthoftheteeth butthelatterismaybeunderestimatingbecauseamissing fragmentofenamel.Thenewlyfounduppermolarsdonot differfromthosedescribedinpreviouspublications.

3. Discussion

ThisisthethirdpublicationinwhichKyawdawialupina isreported,theﬁrstbeingEgietal.(2005)andthesecond Peigné et al. (2007). Because of its relative abundance, thisspecieswasprobablythemostcommoncarnivorous mammal in the Pondaung area during the end of the middleEocene.It was probablyanopportunistic feeder likearesomeoftheextentcanids.Themorphologyofthe lowermolarsdisplayssomecuttingareasalongthebuccal faceofthetrigonidaswellaslargetalonidsdedicatedtoa crushingfunction.Thenewmaterialprovidesnewdetails ofcharactersofthelowermolarsandprincipallythoseof theupperP4whichwasquiteunknownuntilnow.

HyaenodontaVanValen,1967 HyaenodontoideaLeidy,1869 HyaenodontidaeLeidy,1869 HyaenodontinaeLeidy,1869 PropterodonMartin,1906 Propterodonpanganensisnov.sp.

Holotype:dentarywithp4–m1,alveoliofm2andm3 (NMMP-Pg1-2011-29).

Etymology:fromthename ofthelocality wherethe specimenwasrecorded.Diagnosis:smallsizedPropterodon with a low and trenchant p4having a trenchant small talonid. Mesiodistally ﬂattened trigonid of m1 without metaconidandshorttrenchanttalonidwithasmallnar- rowpostfossid. Presenceof individualizedhypoconidin m1.Completeabsenceofcingulid.

Differentialdiagnosis:differsfromHyaenodonandother hyaenodontidsbytheshapeofp4,andtherelativelarge sizeofm1.Propterodonmorrisi(=P.irdinensis)differsby itslargersize,thelargertalonidofm1andthepresenceof aminutemetaconidinmolars.P.pishigouensisdiffersby itslargersize,witharelativelylargerandpowerfulp4of whichthemaincuspisdistallytiltedwithverydeveloped accessorymesialanddistalcuspids.P.tongidiffersbyits largersize,morerobustdentary,and,followingTongand Lei,1986,am1similartothatofP.irdinensis(withaminute metaconid?).

Typelocality:Pangan1,Myanmar.

Geologicalage:upperpartofthePondaungFormation, 40–37Ma,almostequivalenttotheEuropeanBartonianor MP15–MP16(EuropeanLandMammalAge).

Distribution:Pondaungformation(Myanmar)only.

Measurementsinmm:p4length5.5,width2.15,height 5.06. m1L5.1, trigL 4.16,trigw 2.73,trigh4.2, talw 1.6.

m2L(6.5),m3L(7.5)Heightandwidthofthedentary:level p3–p4 10.3×5.3;level p4–m110.6×4.9; level m1–m2 11×4.6;levelm2–m311.5×7.7.Heightofthecoronoid process:21.7mm.()=measuredfromalveoli.

4. Description

This taxon is represented by an incomplete dentary bearing p4–m1(Fig.2A–C)and partof themesialalve- olusandthedistal alveolusofp3,alveoliofm2andm3 withpiecesofthetoothroots andthecoronoidprocess (NMMP-Pg1-2011-29).Beyonditsfarsmallersize,itdif- fersdramaticallyfromKyadawialupinabyitsmorphology andprobablybyitsecologyanddiet.Itbelongsclearlyto adifferentgenusundescribedinMyanmaruntilnow.The dentaryisslender,shallowwiththelowerborderslightly concaveandslightlytaperingforward.Themesialborderof thecoronoidprocessisveryobliquewithanangleof134^◦ relativelytothehorizontallineofthetoothrow.Partofthe distalsurfaceandtheangularareaaremissingoff,butit seemsthatitwasventrallypointed.Themassetericfossa iswidebutnotespeciallydeep.Itextendsbeneathm3and isdorsallylimitedbyarobustridgealongthemesialbor- derofthecoronoidprocess.Lingually,ashallowdepression mesiallylimitedbyamoderateridgecorrespondstothe temporalmuscle.Thepositionofthemandibularcondyleis visible:itislocatedbelowthetoothrow.Thep4iscomplete exceptafragmentofenamelmissingfromthebucco-distal corner. Itis almostashighasm1witha triangularlat- eraloutline.Aweakparalophidendsatthebaseofasmall mesio-lingualparaconid.Distallythereisasmallbutclear talonidwithahypoconidofwhichthetopisobliterated byasmallwearfacetand,linguallyanarrowandshallow basinlimitedbyalowentocristid.Thereisnotraceofa

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Fig.2.Propterodonpaganensisnov.sp.(Pg1-2011-29).Fragmentofdentarywithp4–m1.A.Lingualview.B.Buccalview.C.Occlusalview(stereo).Scale bar=10mm.

Fig.2. Propterodonpaganensisnov.sp.(Pg1-2011-29).Fragmentdemandibuleavecp4–m1.A.Vuelinguale.B.Vuebuccale.C.Vueocclusale(stéréo).

Échelle=10mm.

cingulid.Theparaconidofm1islowerthantheprotoconid anditiselongatemesiallyandslightlylinguallydirected.

Theprotoconidistransversallyﬂattened.Theprotoconid isshifteddistally.Awide quasiverticalwearfacetwith verticalstriationsextendsinthebuccalsurfaceofthepara- conidandlargepartoftheprotoconid.Themetaconidis absent.Ashorttalonidcomposedbyaconicalhypoconidis alignedontheprotoconidandseparatedfromitbyabuc- caldepression.Averyshortentocristidispresentbutdoes notreachthemetaconid,leavingthesmalltalonidbasin linguallyopen.Likeinp4,thereisnocingulid.

5. Comparisonsanddiscussion

ThefossilfromPondaungfaunashareswiththeHyaen- odon species the distally shifting of the protoconid on m1,theabsenceofmetaconid,theveryobliquecoronoid process,thecoronoidprocesslongerthanhigh,theven- trally curved angular process, and the wide masseteric fossa.ThesefeaturesdistinguishthePondaungtaxonfrom hyainailourines (e.g., Pterodon) and teratodontines (e.g., Dissopsalis),twohyaenodontsubfamiliesthatconvergently acquiredhypercarnivorousdentition(Borthsetal.,2016).

Themorphologyofthem1(longanddistallyshiftingofthe protoconid)distinguishesthePondaungtaxonfromhyper- carnivorousproviverrinessuchasOxyaenoides–thelatter genusactuallysharesmandibularfeatureswithHyaenodon (Soléetal.,2015).

Weestimatedtheindex(Lm1/Lp4)×100forsomeof theoldestHyaenodonspecies. Itequals 74in theNorth AmericanH.venturae(thisspeciespossessestherelatively longestm1amongHyaenodon(LavrovandEmry,1998)), 69inH.minor,68inH.brachyrhynchus,H.requieni,and H.eminus.Thisindex actuallyequals 93in NMMP-Pg1- 2011-29.Therefore,thePondaungfossildiffersfromthe Hyaenodonspeciesbytherelativesizeofthem1:thelatter is indeed longer than in Hyaenodon. Thisfeature is primitiveamonghyaenodontids.Moreover,thespeciesof Hyaenodonhaveﬂattenedandshearinglowermolarswith- outmetaconidbutp4isnormallymorerobustrelativeto NMMP-Pg1-2011-29,farhigherthanm1andmoreconical.

Consequently,NMMP-Pg1-2011-29doesnotrepresenta Hyaenodonspeciesdespitethepresenceofsimilardental andmandibularfeatures.

PropterodonistheclosestrelativetoHyaenodon(Borths etal.,2016).Propterodonmorrisi,MatthewandGranger, 1924(=P.irdinensisMatthewandGranger,1925)fromthe EoceneofMongoliaisfoundedonadentarywithp3,m1, m3andthealveoliofp1,p2,p4andm2.Itisclosebythe sizetoNMMP-Pg12011-29(MatthewandGranger,1925, Fig.3).Unfortunately,theabsenceofp4doesnotallowany comparisonofthattoothbutm1isdifferent“withrather large,high-crestedheelnearlyasbroadasthebodyofthe tooth,aminutemetaconid,paraconidconsiderablysmaller andlowerthanmetaconid”(MatthewandGranger,1925, p. 4). In NMMP-Pg1-2011-29, the paraconid cannot be lowerthanthemetaconidwhichisabsent,theprotoconid

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Fig.3. Hyaenodontaindet.sp.(PK56-12-10).Fragmentofdentarywithtalonidofm2andthecompletem3.A.Lingualview.B.Buccalview.C.Occlusal view(stereo).D.Radiographyshowingtherootsofm2andm3.Scalebar=10mm.

Fig.3. Hyaenodontaindet.sp.(PK56-12-10).Fragmentdemandibuleavecletalonidedem2etm3complète.A.Vuelinguale.B.Vuebuccale.C.Vue occlusale(stéreo).D.Radiographiemontrantlesracinesdelam2etlam3.Échelle=10mm.

isless highrelative tothe paraconidand thetalonidis relativelysmallerthanthatofP.irdinensisanditisnar- rowerthanthetrigonid.Anotherspecies,fromtheEocene ofChina,isattributedtothegenuswithaquestionmark?

PropterodonpishigouensisTongandLei,1986.Thistaxonis knownfromapieceofdentarywithp4–m1.Itdiffersbythe largesizeofp4,theprotoconidofwhichbeingveryhigh anddistallytilted,withrelativelylargermesialanddistal accessorycuspids,them1witha largeandhightalonid (Tong and Lei, 1986, Fig. 2). Another dentary bearing p1–m3isthetypespecimenofPropterodontongiLiuand Huang,2002.ThatmandiblediffersfromthatofPondaung byits largersize (height of thedentary at p4–m114.5 against10.6,atm1–m315.4against11.5:and lengthof p45.5against8,Lm16.5for5.1).Theventralborderofthe dentaryisgoinguprapidlyandisstayinginahorizontal lineinNMMP-Pg1-2011-29(LiuandHuang,2002,Fig.1).

Theteethare alsodifferent,p4ofP.tongi bearsa clear paraconidandalargertalonid,whilem1ofP.tongiisworn outandwejustcanseethatitissmallerrelativelytop4.

Regardingtherelativesizesofthep4andm1,theindex

(Lm1/Lp4)×100equals81inP.tongiand80inP.iridensis (unpublishedspecimen).Thespecies?P.pishigouensishas anindexclosetothatofthePondaungtaxa:95vs93.

Toconclude,weconsiderthatPg1-2011-29represents anewspeciesofPropterodon.

HyaenodontaVanValen,1967 Familyindet.

Hyaenodontaindet.sp.

NMMP-PK56-12-10isafragmentofdentary(Fig.3A–D) withthemesialrootandthetalonidofm2andthecom- pletem3.Itstoothmeasurements(mm)are:Lm2=(5.43);

talwm2=1.71;Lm3=3.76;Ltrgm3=2.12:trhm3=2.22;

trwm3=2;tlwm3=1.2.

The dentary is deep relatively to its width [index (w/h)100=45.5].Thedistalrootofm1isrobust.Themesial rootofm2islarge,inthetalonid,ahighandrelativelytren- chanthypoconidhasaconvexbuccalsurfaceandaslightly convex,almostﬂat,verticallingualsurfacewhilethethin verylowentocristidlimitslinguallyanalmostﬂattalonid basin.Thetalonidisslightlytaperingdistally.Thereisno

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hypoconulidbutasmallnotchseparateshypoconidand entocristid.Inm3,theenamelisslightlyweathered.The protoconidoverlooksthehightrigonidwithalingualface onlyslightlyconvex.Thepostparacristidisveryoblique, almostperpendicular,relativelytothetoothrowaxis.The baseoftheparaconidcontactsthatofthemetaconid.The latterislessvoluminousbutashighastheparaconidand,in occlusalview,thetrigonidisVshapedinisoscelestriangle.

Themetaconidisslightlymoredistalthantheprotoconid.

Thetalonidisnarrowandhighbecausethesizeandshape ofthehypoconid.Thereisnotalonidbasinbutasurface sloping gently toward thelingual border without clear entocristidnorentoconid.Itisdifﬁculttodistinguishthe wearfacetsbutitseemsthatthereisoneshearinginfront oftheprotoconidand,partly,theparaconidandanother oneonthewallconstitutedbythedistalsurfaceofthepro- toconidandmetaconidwhicharebothinasameplane.Like aroundthetalonidofm2,thereisnotraceofanycingulid aroundthetooth.

6. Comparisons

The comparisons will deal with thehyaenodonts of whichm3isreducedrelativetom2:ourcomparisonthus willfocusonGalecyonandonLimnocyoninae.

ThegenusGalecyonhasbeendescribedinNorthAmer- ica(GingerichandDeutsch,1989;Zack,2011)andEurope (SmithandSmith,2001).Therelativereductionofm3is mentioned intheoriginaldiagnosisasoneofthemajor featuresofthishyaenodontgenus(Zack,2011).

Wecanmeasurethereductionofthelastmolarrela- tivelytom2(index(Lm3/Lm2)×100).Thisindexis69in thePondaungfossil,97inGalecyonmorloi,77inGalecyon peregrinus,68inG.mordaxand64inG.chronius(meansof severalspecimensforthelatter),higherforthetwoformer speciesbutclosetothatofPondaunginthelatterone.

InNMMP-PK56-12-10,thedentary isrelativelydeep like in Galecyon but the trigonid of the m3 is more openandthelingualcuspidsclearly separated,thepro- toconidislowerrelativetotheparaconid,themetaconid is slightly more distal,and theparaconid is lowerwith apostparacristidmoreelongateanddirectedmoredisto- mesiallyandnotmoreconicalasinGalecyon.Thetalonidof Galecyonhasarobusthypoconidandacristaoblicadirected towardtheprotoconidlikeinNMMP-PK56-12-10butthe basinisdeeperwithanentocristidslightlyhigher.Despite thecommonpresence of a reduced m3,thedifferences betweenthem3oftheAsianfossilandtheGalecyonspecies –especiallytheopeningofthetrigonidandlengthofthe paracristid–implythatitishard toreferthePondaung taxontoGalecyon.

The Limnocyoninae are ﬁrst recorded in the late Palaeoceneof Asia(Menget al.,1998), buttheymainly radiatedintheearlyandmiddleEoceneofNorthAmer- ica(Gunnel,1998).ThewholesubfamilyLimnocyoninaeis characterizedbym3reducedorabsent(MorloandGunnell, 2003, 2005; Polly, 1996). The m3 is absent in Limno- cyonMarsh,1872a,ThinocyonMarsh,1872b,Oxyaenodon Wortman, 1899,and Iridodon Morloand Gunnell,2003.

InProlimnocyonMatthewandGranger,1915,m3isdra- maticallyreduced.Theindexm3/m2isverylow(63)in

P.chowiMengetal.,1998–theoldestlimnocyonine–and inP.haematusGingerichandDeutsch,1989(meansofsev- eralspecimensforthelatter),(43)inP.atavusMatthewand Granger,1915,andthem3isknob-likeinP.antiquus(Morlo andGunnell,2003,ﬁg.18)sofarmorereducedthanthatof NMMP-PK56-12-10.Them3ofP.chowirecallsthatofthe PondaungtaxoninhavingaVshapedtrigonid(inocclusal view)andametaconidslightlymoredistalthantheproto- conid.However,them3ofP.chowidiffersfromthatofthe Pondaungtaxoninhavingapostparacristidclearlyshorter andmoretransversallyalignedandlargehypoconulidand hypoconid.Them3ofP.atavusismoresimilarinhavinga longerandmoreobliquepostparacristid,but,asmentioned above,them3ismuchmorereducedcomparedtothem2 –theelongationand modiﬁcationof thepositionofthe postparacristidcouldcorrespondtoaconvergencetowards moresecantteeth.Therefore,basedonthesecomparisons, thefossilfromPondaungcouldrepresentataxondifferent fromtheLimnocyoninae.

FollowingtheobservationsofSmithandSmith(2001) basedonthehyaenodontsfromDormaal,ithasbeenpro- posedthatm3wasslightlysmallerthanm2intheearliest hyaenodonts(Solé,2013;Soléetal.,2013).Basedonthis postulate,onehypothesizedthat(1)therelativesizeofm3 increasedinseveralgroupsofHyaenodonta(e.g.,Proviver- rinae,Hyaenodontinae),whereas(2)therelativesizeofm3 decreasedintheLimnocyoninaeandGalecyon.Regarding thishypothesis,thePondaungtaxoncouldrepresentathird lineagethatexperiencedsuchreduction.

7. Overallconclusion

ThePondaungFormationhadproducedatleastthree differenttaxaofHyaenodonta,Kyawdawialupina,Yarshea cruentaandOrienspterodondahkoensis.Twoindeterminate species,werealsodescribed,Proviverrinaeindet.forafrag- mentofmandibleinEgietal.(2005)andHyaenodontidae sp.indet.inPeignéetal.(2007)fora largeM3,noneof themmatchingthenewmaterial.Thus,thetwonewcar- nivoroussigniﬁcantly augmentthelistofthePondaung predators.Thelargerspecies,O.dahkoensis,wouldoccupy theplaceofalargehypercarnivore,thetwomedium-sized YarsheaandKyawdawiaactedlikecanids,theformerbeing probablymorecarnivorousthanthelatter,Propterodonwas asmallhypercarnivoresimilartotheextantMartesand thesmallerspecieswaspreyinguponsmallvertebratesor invertebrates.Theseﬁvespecies,togetherwiththeother indeterminatespecies,constitutedaquitecompleteguild ofpredators.

Concerningthepaleo-biogeography,wenotethatallthe generaarerecordedonlyinMyanmar(YarsheaandKyaw- dawia)or in Myanmar, Mongolia or China(Propterodon andOrienspterodon).Therelationshipsofthesecarnivorous withthoseofothercontinentsarethusactuallyunknown.

However,one can notethat thehyainailourines (Orien- spterodon)andhyaenodontines(Propterodon)recordedin thePondaung Formation, arethe ﬁrstones recordedin theSoutheastAsia.Itisinterestingtonotethatthesesub- familiesappearedalmostcontemporaneouslyinEurope:

hyaenailourinesappearedaroundMP16referencelevel(ca.

39Ma)(Soléetal.,2013)andthehyaenodontinesaround

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MP17a(ca.38Ma)(Lange-Badré,1979).Thehyaenodonts ofthePondaungFormationthusmightillustrateaprofound modiﬁcationofthecarnivorousfaunaamongLaurasia.

Acknowledgements

WethankthevillagersofBahin,Paukkaung,Nyaung- pinle, and Maggyigan of Pondaung area and their authoritiesfortheirhelp,kindnessandenthusiasmwhich greatlyfacilitatedourfieldwork.WearegratefultoSabine Riffaut(IPHEP)forherworkonthephotosbyLdeB,Arnaud Mazurier(Univ.Poitiers)fortheCT-scansections.Wealso thank XavierValentin and Mana Rubgumrung for their participationtothe fieldwork and theirtechnicalassis- tanceandChristopherBeardfor hisparticipationtothe fieldwork.ThisworkhasbeensupportedbytheANR-09- BLAN-0238-02Program,CNRSUMR7262,theUniversity of Poitiers, the Ministry of Culture of the Republic of the Union of Myanmar, a 2015 grant from the Leakey foundationand NationalGeographic grant number NG- W344-14.F.S. wasfinancially supportedby theFederal Science Policy Office of Belgium (Belspo Brain Pioneer projectBR/175/PI/CARNAGES).

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