A new Placoderm fish (Acanthothoraci) from the Early Devonian Jauf Formation (Saudi Arabia)

Geodiversitas

Hervé Lelièvre¹  Dominique Janjou¹  Sébastien Olive¹  Daniel Goujet¹ 

关键词: Acanthothoraci;    Placodermi;    Arabosteus variabilis n. gen;    n. sp.;    arthrodiran model;    endocranium;    homology;    skull roof plate;    Saudi Arabia;    new genus;    new species;    Acanthothoraci;    Placodermi;    Arabosteus variabilis n. gen.;    n. sp.;    modèle arthrodire;    endocrâne;    homologie;    plaque du toit crânien;    Arabie Saoudite;    genre nouveau;    espèce nouvelle;   

DOI  :  10.5252/g2011n3a1

学科分类：生物科学（综合）

来源: Museum National d Histoire Naturelle

【 摘 要 】

Anexceptionallywell-preservednewacanthothoracid(placodermfish)presentingcompleteendocraniumandskullroof,fromSaudiArabia(QasrLimestoneMember,JaufFormation),EarlyDevonianinage,isdescribedasArabosteusvariabilisn.gen.,n.sp.ComparedtootherAcanthothoraci,thenewtaxonexhibitsaskullroofvariableinitsdermalplatedistribution(e.g.,asupernumeraryplate:theposteriorcentralplate)andsensorylinepattern.Eventhedifferentspecimensofthistaxonshowsuchvariabilitybetweenthem.Arabosteusvariabilisn.gen.,n.sp.enlargesthescopeofourknowledgeofAcanthothoraciandPlacodermiingeneral.Traditionally,theArthrodira,oneofthehistoricallyearliestdescribedgroups,providethestandardreferencemodelfortheplacodermskullroofpattern.TheinterpretationoftheacanthothoracidskullroofpatternoftheSauditaxonfromanarthrodiranmodelandtheestablishmentofhomologiesisimpossibletoresolveunlessbasedonpriorassumptions(e.g.,hypothesisoffragmentationorfusionfortheparanuchalplatecomplex).ThelaterallinesystemofA.variabilisn.gen.,n.sp.isunstable(e.g.,presenceorabsenceofthepostmarginalsensorylinecanal)makingitambiguoustodefinebonehomologyandterminology.Consequentlyspatialdistributionofskullroofplateshasbeenretainedforsuchataskwithaminimalreferencetotheinstablefeaturesofthesensorylinegroovedistribution.

【 授权许可】

Unknown