Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny and palaeobiology

Geodiversitas

Christine Argot¹  Sandrine Ladevèze¹  Christian De Muizon¹  Florent Goussard¹  Guillaume Billet¹ 

关键词: Pantodonta;    early Palaeocene;    Bolivia;    Anatomy;    Functionnal anatomy;    Phylogeny;    Palaeobiology;    Pantodonta;    Paléocène inférieur;    Bolivie;    Anatomie;    Anatomie fonctionnelle;    Phylogénie;    Paléobiologie;   

DOI  :  10.5252/g2015n4a1

学科分类：生物科学（综合）

来源: Museum National d Histoire Naturelle

【 摘 要 】

AlcidedorbignyainopinataMuizonamp;Marshall,1987isabasalpantodont(Placentalia,Mammalia)ofsmallbodysize,fromtheearlyPalaeoceneoftheSantaLuciaFormationatTiupampa,Bolivia.TiupampaisthetypelocalityfortheTiupampan,aSouthAmericanLandMammalage(SALMA),whichisassignedanageequivalenttothebasalTorrejonian1ofNorthAmerica(c.65Ma).Alcidedorbignyaisknownbyexceptionallypreservedspecimens,whicharedescribedhere.Thetwomajorspecimensareanalmostcompleteskeleton(MHNC8372)andapartialskull(MHNC8399),theformerrepresentingoneofthebest-preservedfossilplacentalsfromtheearlyPalaeoceneandprobablytheoldestplacentalskeletonthatissocompletelyknown.ThesespecimensarealsothefirsteutherianskullsandskeletoneverdiscoveredatTiupampa,alocalitywhichhasyieldednumerousmetatherianskullsandpartialskeletons.Theremarkablepreservationofthetwoskullsallowsadetaileddescriptionofthecranialanatomywithwell-identifiedsuturesandforamina,includingthoseoftheauditoryregion.ThroughCTscanningoftheskulls,thearterialandvenouscirculationpatterninthebasicraniumaswellasthebonylabyrinthoftheinnerearweretentativelyreconstructed.AthoroughdescriptionofthepostcranialskeletonofMHNC8372isalsoprovided.Amongpantodonts,AlcidedorbignyapresentstheclosestmorphologicalsimilaritieswithPantolambda,theoldestandearliestdivergingNorthAmericanpantodont(knownbyskullsandskeletons),fromthelateearlyPalaeocene(Torrejonian2and3)ofNewMexico.Alcidedorbignyaisone-thirdthesize,muchmoregracile,andclearlyexhibitsmoreplesiomorphicfeaturesthanPantolambda.Itisalsoatleast3Maolder.InterestingsimilaritiesarealsoobservedbetweentheskullofAlcidedorbignyaandseveral“condylarths”,suchasMaiorana,Baioconodon,Arctocyon,andArctocyonides.ThebasicraniumofAlcidedorbignyaisalsosimilartothatofsomeextantafrotheres(e.g.,Tenrec)orLipotyphla(e.g.,Solenodon),butmostofthesesimilaritiesmayrepresentplacentalsymplesiomorphies.Infact,thecranialanatomyofAlcidedorbignya,beyondthesimplethoroughdescriptionofabasalpantodont,shedslightonthecranialanatomyofplacentalsfromtheearliestPaleocene,previouslyunknowninthisdetail.ThepostcranialskeletonofMHNC8372togetherwithsomeisolatedspecimensreferredtoA.inopinata,iscomparedtoadequatemorphofunctionalmodels(e.g.,Solenodon,Dendrohyrax,Sciurus),whichindicatesthatitwasamoderatelyagile,plantigrade,generalizedterrestrialmammalwithgoodclimbingability(scansorial)andoccasionallycapableofstandinginabipedalposition.Thescutiformungualphalangeswereprobablybearingnail-likehooves(orprimate-likenails)andbecauseoftheabsenceofclaws,fossorialhabitsareunlikely.

【 授权许可】

Unknown