Mode of life of Early Devonian Orthonychia protei (Neritimorpha, Gastropoda) inferred from its post-larval shell ontogeny and muscle scars

Bulletin of geosciences

Frýda J¹  Frýdová B¹  Racheboeuf PR¹ 

关键词: Gastropoda;    muscle scars;    ontogeny;    Orthonychiidae;    Early Devonian;    W France;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

RichfossilmaterialoftheEarlyDevonianOrthonychiaprotei(Oehlert,1883)fromtheSaintCéneréFormation,Brittany(France)providesauniquechancetoanalyzetheinfraspecificvariabilityofmusclescarsandpost-larvalshellmorphology.Thepositionofthemusclescarinthisspeciesdependsontheshapeoftheteleoconch,whichseemstobeinfluencedbyitslivingpositionuponthecrinoidhost.Individualshavingateleoconchaperturewithapentagonaloutlineandfiveaperturalprocessesprobablylivedontopofacrinoidcalyxandtheirmusclewasattachedtothecenteroftheirteleoconchs.However,musclescarsaresituatedmorelaterallyinindividualswithirregularteleoconchslackingaperturalprocesses.Thelattergroupwasprobablyattachedtoanotherpartofthecrinoidbodyoreventoanothertypeofhardsubstrate.Juvenilepost-larvalOrthonychiaproteiwasamobileanimal,butveryearlyinitsontogenybecameadaptedtoafixedpositiononthecrinoidbodyandremainedimmobileforthemajorityofitspost-larvalontogeny.Long-termcoexistenceofOrthonychiaproteiwiththesamecrinoidsuggeststhatthisspecieshadalong-termadvantagefromsuchanecologicalstrategy.However,theexistenceofindividualswithirregularlyshapedteleoconchssuggeststhatOrthonychiaproteicouldalsolivesuccessfullyoutsideofthedigestiveopeningsofcrinoidsand,thus,useafoodsourcenotcloselyconnectedwithcrinoids.ThisinterpretationcanbesupportedbythefactthatatleastsomeSilurianandDevonianplatyceratidswereadaptedtolivingonsmallfirmobjects(likeemptycephalopodshells)lyingonthesedimentsurface.

【 授权许可】

Unknown