New skulls of Kolpochoerus phacochoeroides (Suidae, Mammalia) from the late Pliocene of Ahl al Oughlam, Morocco Denis Geraads To cite this version: Denis Geraads. New skulls of Kolpochoerus phacochoeroides (Suidae, Mammalia) from the late Pliocene of Ahl al Oughlam, Morocco. Palaeontologia Africana, 2004, 40, pp.69-83. halshs-00004898 HAL Id: halshs-00004898 https://halshs.archives-ouvertes.fr/halshs-00004898 Submitted on 10 Oct 2005 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1 NEW SKULLS OF KOLPOCHOERUS PHACOCHOEROIDES (SUIDAE, MAMMALIA) FROM THE LATE PLIOCENE OF AHL AL OUGHLAM, MOROCCO by GERAADSDenis UPR2147duCNRS,44ruedel'AmiralMouchez,75014PARIS,France [email protected] 2 ABSTRACT.Thediscoveryoftwomaleskullsof Kolpochoerus phacochoeroides inthelate PlioceneofAhlalOughlaminMorocco,andtherevisionofthewholecollectionfromthis locality,allowstoextendthedescriptionofthisNorthAfricanform,toestimateitssexual dimorphismandtheextentofindividualvariationinalargeisochronoussample,toreveal someontogenicchanges,andtoconfirmitsdistinctionasaspeciesofitsown,asitscranial proportions(largeoccipital,shortsnout)andtoothcharacters(lackofenamelonupper canines,reducedincisorsandpremolars,complicatedthirdmolars)setitclearlyasidefrom theEastandSouthAfricanforms.Acladisticanalysisshowsthat K. phacochoeroides and Hylochoerus aretheterminalbranchesofthe Kolpochoerus clade,whichisthesister-group of Potamochoerus . Keywords: Africa, Pliocene, Pleistocene, Suidae, Mammalia, Kolpochoerus , cladistics Tableofcontents INTRODUCTION 2 SYSTEMATICPALEONTOLOGY-Genus Kolpochoerus 3 Currentlyrecognisedspecies 4 Sexualdimorphismin Potamochoerus 4 The Kolpochoerus fromAhlalOughlam 5 Phylogenyof Kolpochoerus 14 ACKNOWLEDGEMENTS 18 REFERENCES 18 INTRODUCTION ThelatePliocenesiteofAhlalOughlaminMoroccohasbeenexcavatedunderthe author'sleadership,aspartofthe"ProgrammeCasablanca"oftheInstitutNationaldes Sciencesdel'ArchéologieetduPatrimoineofRabat.Itistherichestfossillocalityofthe NorthAfricanNeogene,withabout55speciesofmammals(Raynaletal.1990,2001; Geraads1993,1995,1996,1997,2002;Alemseged&Geraads1998;Geraads&Amani 1998;Geraadsetal.1998;Geraads&Metz-Muller1999).Theformationofthesitewas probablyinstantaneousatthegeologicalscale,andthewholecollectionisthusclosetoa singlebiocœnosissample. In1993,Ipublishedadescriptionofthematerialof K. phacochoeroides availableat thattime.Theamountoffossilsrecoveredfromthissitehasgreatlyincreasedsincethen,and 3 about500specimens(manyofthemfragmentary)havenowbeenidentified.Insharpcontrast toEastorSouthAfrica,thereisstillnoevidenceofanyothersuidspecies.Thebestnew specimensaretwovirtuallycompletemaleskulls:AaO-3655,inverygoodcondition,and AaO-3656,whichiscrushed.Relationshipsofthisspeciescannowbemuchbetterevaluated bycomparisonwiththelivingforms,especially Potamochoerus and Hylochoerus ,thatare usuallyrecognisedasbelongingtothesameclade,andwithotherspeciesfromvarioussites, mostlythosefromEastAfricahousedintheNationalMuseumsofEthiopia(NME),Kenya (KNM)andTanzania(NMT).ThematerialfromAhlalOughlamishousedattheInstitut NationaldesSciencesdel'ArchéologieetduPatrimoine,Rabat,Morocco. Abbreviations:AaO:AhlalOughlam;ASB:Asbole(earlyMiddlePleistoceneof Ethiopia:Geraadsetal.inpress);MNHNP:MuséumNationald'HistoireNaturelle,Paris. SYSTEMATIC PALEONTOLOGY Genus Kolpochoerus vanHoepen&vanHoepen,1932 Mesochoerus Shaw&Cooke,1941 Omochoerus Arambourg,1943 PromesochoerusLeakey,1967 Ectopotamochoerus Leakey,1967 Type-species : K. sinuosus vanHoepen&vanHoepen,1932 Diagnosis :although Kolpochoerus isoneofthemostcommonandfrequentlydescribed suidsoftheAfricanPlioPleistocene,andalthoughgeneralagreementastothecontentofthe genushasmoreorlessbeenreached,theavailablediagnosesofthegenusvarywidely.Many authorsdonotprovideanydiagnosis(Hendey&Cooke1985;Geraads1993;Pickford1994; Brunet&White2001).Othersprovideonlyverygeneralprimitivefeaturesthatcouldapply tomanysuids(sexualdimorphism,brachyodontteeth,generalresemblanceto Sus and Potamochoerus ),orarevariable(especiallythosewhichapplyonlytothelatestmembersof thegroup,suchashypsodonty,cementcover,lengthoftalon/id).Onlyafewvalidfeatures aregenerallyrecognised,startingwiththeoriginaldiagnosis(vanHoepen&vanHoepen 1932:59;mytranslation):"Molarswhosepillarshavestronglyfoldedenamel.Thepillarsof themiddlerowarequitesimple.Betweenthefirstandsecondpairofpillars[ofM3/m3] standsamedianpillar,butbetweenthesecondandthirdpairsstandtwotriangularpillars, opposedbytheirbases." 4 Cooke(1978)providedalonglistoffeatures,ofwhichthefollowingarethemost diagnostic:zygomaexpandedanddrooping,caninesresemblingthoseof Hylochoerus ,upper premolarswithprotocone,molarswithpillarshigherandmoredistinctthanin Sus and Potamochoerus ,P4complicated,mandibleinflated. Thecladisticanalysis(seebelow)suggeststhefollowinglistofapomorphicfeatures: broadforehead,concavecranialprofile,zygomaticshelfdeepandpneumatized,P2well behindtherootofthecanine,P3withananterolingualcusp,apairofcentralpillarsbetween thesecondandthirdpairsonm3. Currently recognised species ThedescriptionbelowisbaseduponthemaleskullsAaO-36555andAaO-3656.They willbecomparedwiththefemaleskullAaO-239(Geraads1993),withthelivingforms,and withtheother Kolpochoerus species,whichare: - K. paiceae (Broom,1931)fromthePleistoceneofSouthAfrica(Hendey&Cooke1985); - K. majus (Hopwood,1934)fromthePleistoceneofEastAfrica,representedbyseveral skulls,onlyafewofwhichhavebeendescribed(Gilbertetal.2000;Geraads&al.inpress a); - K. heseloni (Leakey,1943),whichincludes K. olduvaiensis ,alateandderivedform, appearstobethecorrectnameforthespeciesoftencalled K. limnetes (seePickford1994and Cooke1997),fromthePlioPleistoceneofEastAfrica; - K. maroccanus (Ennouchi,1953),apoorlyknownspeciesfromMorocco;theageofthe typeisunknown,butareferredM3isoflateearlyPleistoceneage(Geraads&al.,2004); - K. afarensis Cooke,1978,fromthePlioceneofEastAfrica; - K. deheinzelini Brunet&White,2001,fromtheearlyPlioceneofEthiopiaandChad; - K. cookei Brunet&White,2001,fromthelatePlioceneofEthiopia. Sexual dimorphism in Potamochoerus Amongtheabove-mentionedspecies,thebest-knownformis K. heseloni ,followedby K. afarensis , K. paiceae and K. majus ,whiletheremaining3speciesareknownonlyby teeth.However,almostallknown K. heseloni skullsareofmaleindividuals,while K. paiceae isknownonlybyfemaleskulls.Inordertolimittheeffectsofthisdrawbackonthe comparisons,Ihavetriedtoevaluatethesexualdimorphismin Potamochoerus ,theonly closerelativeofthefossilgenuswhichcouldbeillustratedbyenoughspecimens(16females and18males,allfullyadult,fromtheMNHNP). 5 In Potamochoerus ,malesareslightlylargerthanfemales,forallskullmeasurements, butallofthesewidelyoverlap,anddifferencesbetweenbothsexesamounttoonlyafew percent(Table1).ThisagreeswiththefindingsofMade(1991).Themostsignificant differencesareinmuzzlelength,andbi-auditoryandminimumorbitalwidths.Bi-zygomatic widthoffemalesentirelyfallswithinthemalerange,althoughthenarrowermalesareof ratheryoungspecimens. Table 1 about here Morphologicalfeaturesallowingsexualidentificationmustbeusedwithcaution.The anteriorborderofthezygomaticarchismoretransversalinmales,andmoresloping backwardsinfemales.Thezygomaispneumatizedinmales,lessso(andoftennotatall)in females.Thesamedifferencesholdfor Hylochoerus butinthisgenus,eventhefemaleshave inflatedarches. Themostconspicuoussexualdifferenceliesinthesupra-canineflange,whichextends upwardsin Potamochoerus malesmorethaninanyothersuidgenus,asathinlaminaofbone endinginaroughenedthickening,sometimesreachingthelevelofthenasals,whicharewide androughinadultmales.Femalesnormallyhavealmostnosupra-canineflange,and smoothernasals,butoneoftheexaminedspecimens(withnoregisteredsexdata),although femalebymostofitsotherfeaturesandmeasurements,hasastrongcanineflange,sothat thereisadoubtconcerningthediscriminantvalueofthisfeature. Turningnowtothefossilforms,theonlywellpreserved(unpublished)femaleskullof Kolpochoerus heseloni fromPeninj(NMT;photosofthespecimenwerealsokindlyprovided byH.B.S.Cooke)displayssimilarsexualdifferencesfromthemaleones.Thesupra-canine flangeisweak,butskulldimensions(Hendey&Cooke1985)areonlyslightlysmallerthan inmales.Thesameholdsfor K. phacochoeroides ,inwhichthemaindifferenceliesincanine size.Thereis,therefore,everyreasontobelievethatsexualdimorphismwasnotparticularly greatinthisgroup,andthatthefemaleskullsprovideagoodideaofwhatthemaleskulls were. The Kolpochoerus from Ahl al Oughlam Kolpochoerus phacochoeroides (THOMAS,1884) Sus phacochoeroides Thomas,1884:10 6 Holotype :mandiblefragmentfromthelimestonesofAïnelBey,Algeria(Thomas,1884, pl.10,fig.12).MNHNP,N°AFN-1.BesidesAhlalOughlam,itisnotknownfromanyother locality. Diagnosis :convexparietalprofile,auditoryductveryoblique,occipitalhighandbroad,with condyleshighabovethetoothrow,droopingzygomaticarch,supra-canineflangeandsnout musclescarsusuallyweak,snoutshortandroundedinsection,auditorybullasmall,upper caninelarge,withtrifoliatecross-section,enamelbandvestigialorabsent,lowercanineof verrucosus type,I1small,markedweargradientoncheekteeth,premolarsreducedinsize, P4withaposterolingualfovea,M3/m3withcomplextuberclesandnumerousaccessory pillars,butnormallywithonlyonepillarbetweenthesecondandthirdpairsofm3.