Sarotrocercus oblitus - Small arthropod with great impact on the understanding of arthropod evolution?

Bulletin of geosciences

Maas A¹  Haug JT¹  Waloszek D¹  Haug C¹ 

关键词: Burgess Shale;    Cambrian;    Arthropoda sensu stricto;    Euarthropoda;    ontogeny;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

SarotrocercusoblitusisasmallarthropodfromtheCambrianBurgessShale.Itwasoriginallydescribedwithashortheadwithonlytwoappendage-bearingsegments(thefirstappendagebeinglimb-shaped),ashorttrunkofninesegmentsandlamellatetrunklimbs.Thisrather“unusual”morphologyinspiredvariousauthorstoproposeevolutionaryscenariosconcerningsegmentationandappendages.TheheadofS.oblitusservedalsoforscenariosabouttheevolutionofthearthropodhead,becauseitseemedtodocumenttheevolutionarystepbetweenthelevelofArthropodasensustricto(headwithoneappendage-bearingsegment)andthatofEuarthropoda(headcomprisingfourappendage-bearingsegments).HerewereportthatthemorphologyofS.oblitusdiffersinseveralsignificantaspectsfromitsoriginaldescription,e.g.,inthecompositionofthehead,numberoftrunksegments,andappendagemorphology.Inconsequence,manyearlierassumptionsbasedontheoriginaldescriptionmustberejected.Althoughthematerialconsistsofonlysevenindividuals,ontogeneticvariationofthenumberoftrunksegmentswasobserved,pointingto,atleast,twodevelopmentalstages.Therefore,S.oblitusismorphologicallylessdifferentfromotherCambrianarthropodsthanpreviouslythought,butpossessesaheadwiththreeappendage-bearingsegmentsandlacksaprominentantenn(ul)a.ThesecharacterspointtoapositionofS.oblitusinsideArthropodas.str.,derivingfromthelineagetowardsEuarthropoda.Themorphologyalsoindicatesaspeciallifestyle,e.g.,bythepresenceoflarge,stalkedeyes,apparentlyinconvergencetooneoftheCambrian“Orsten”crustaceanstem-lineagederivatives,Henningsmoenicarisscutula.

【 授权许可】

Unknown