A new marine vertebrate assemblage from the Late Neogene Purisima Formation in Central California, part II: Pinnipeds and Cetaceans

Geodiversitas

Robert W. Boessenecker¹ 

关键词: Marine mammals;    Pinnipedia;    Mysticeti;    Odontoceti;    Pliocene;    Pleistocene;    Purisima Formation;    new species;    Mammiferes marins;    Pinnipedia;    Mysticeti;    Odontoceti;    Pliocene;    Pleistocene;    Formation Purisima;    espece nouvelle;   

DOI  :  10.5252/g2013n4a5

学科分类：生物科学（综合）

来源: Museum National d Histoire Naturelle

【 摘 要 】

ThenewlydiscoveredUpperMiocenetoUpperPlioceneSanGregorioassemblageofthePurisimaFormationinCentralCaliforniahasyieldedadiversecollectionof34marinevertebratetaxa,includingeightsharks,twobonyfish,threemarinebirds(describedinapreviousstudy),and21marinemammals.PinnipedsincludethewalrusDusignathussp.,cf.D.seftoni,thefursealCallorhinussp.,cf.C.gilmorei,andindeterminateotariidbones.Baleenwhalesincludedwarfmysticetes(HerpetocetusbrambleiWhitmoreamp;Barnes,2008,Herpetocetussp.),tworightwhales(cf.Eubalaenasp.1,cf.Eubalaenasp.2),atleastthreebalaenopterids(“Balaenoptera”cortesi“var.”portisiSacco,1890,cf.Balaenoptera,Balaenopteridaegen.etsp.indet.)andanewspeciesofrorqual(Balaenopterabertaen.sp.)thatexhibitsanumberofderivedfeaturesthatplaceitwithinthegenusBalaenoptera.ThisnewspeciesofBalaenopteraisrelativelysmall(estimated61cmbizygomaticwidth)andexhibitsacomparativelynarrowvertex,anobliquely(butprecipitously)slopingfrontaladjacenttovertex,anteriorlydirectedandshortzygomaticprocesses,andsquamosalcreases.Fossilodontocetesincludethelipotid“riverdolphin”Parapontoporiasternbergi(Gregoryamp;Kellogg,1927),fourtrueporpoisesincludingabizarrenewgenusalsoknownfromotherstrata(Phocoenidaeindet.,Phocoenidaeunnamedgenera1and2,andcf.Phocoena),anindeterminatedelphinid(Delphinidaeindet.)apilotwhale-likedelphinid(cf.Globicephalinaeindet.),anundeterminedspermwhale(cf.Physeteroideaindet.),andanindeterminateodontocete.ThenewrecordofParapontoporiasternbergiisnoteworthyasitrepresentsthefirstassociationofanyearbones(petrosal,tympanicbulla,malleus,andincus)fortheextinctgenus.DiscoveryanddescriptionofacompletemarinemammalassemblagepermitsfaunalcomparisonswithotherpublishedPliocenemarinemammalassemblagesfromaroundtheglobe.TheaggregatePliocenemarinemammalassemblagefromeasternNorthPacific(ENP)shareslittleincommonwiththemodernfauna,andismostlycomposedofextinctgenera;notably,phocoenidsandodobenidsweremorediversethanintheENPtoday.ThisindicatesthatthemodernfaunaoftheENPdidnotemergeuntilaftertheendofthePliocene,andprobablysometimeduringtheEarlyPleistocene.ThePlioceneENPassemblageissimilartothatofJapan,andtheNorthPacificingeneralshareslittlewithsouthPacific,Mediterranean,orNorthAtlanticmarinemammalassemblages,indicatingtheNorthPacifichostedaprovincialmarinemammalfaunathatevolvedinisolationfromthemodernmarinemammalfauna,whichhadalreadyappearedintheNorthAtlanticbytheEarlyPliocene.

【 授权许可】

Unknown