Saurichthys and other fossil fishes from the late Smithian (Early Triassic) of Bear Lake County (Idaho, USA), with a discussion of saurichthyid palaeogeography and evolution

Bulletin of geosciences

Jerjen I¹  Kogan I¹  Brinkmann W¹  Jenks J¹  Romano C¹ 

关键词: Saurichthyidae;    Osteichthyes;    coelacanth scale;    biotic recovery;    biodiversity;    cosmopolitanism;    extinction;    palaeobiogeography;    morphological trends;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

AnewmarinefishassemblagefromthelateSmithian(Olenekian,EarlyTriassic)AnasibiritesbedsoftheThaynesFormationcollectednearGeorgetown(BearLakeCounty,south-eastIdaho,USA)comprisesactinopterygians(Saurichthyscf.elongatus,Actinopterygiiindet.),sarcopterygians(Actinistiaindet.),andpossiblychondrichthyans.WereviewtheglobalfossilrecordoftheTriassicloweractinopterygianSaurichthys,whichisusedhereinforacasestudyoftrendsinmorphologicaladaptationsaswellasvariationsinpalaeogeographicdistributionanddiversitydynamicsofEarlyMesozoicfishes.IntheEarlyTriassic,Saurichthysalreadyoccupiedatoppositioninmarinefoodwebs,withsomespeciesachievingbodylengthsofupto1.5m.DistributionofmorphologicalcharactersinSaurichthysduringtheTriassicsuggeststrendstowardsareductioninsquamation,stiffeningofthefinsandaxialskeleton,shorteningofthepostorbitalportionofthecranium,andreductioninthenumberofdermalskullbones.Thepostcranialadaptationsinparticularhelpedtoimprovethefast-startabilityoftheseambushpredatoryfishes.ThepalaeogeographicrangeofSaurichthyschangedfromavirtuallyglobaldistributionintheEarlyTriassic(indicatingrapiddispersalwithinmarineandfreshwaterecosystemsaftertheend-Permianmassextinction)toanoccurrencemainlyrestrictedtothenorth-westernTethysintheLateTriassic,andalsotowardsincreasingraritywithincontinentaldeposits.Modificationsinthepalaeogeographicdistributionwereaccompaniedbysuccessivelossinglobalspeciesrichnessandwerepossiblyrelatedtointra-Triassicextinctionevents,environmentalalterationsand/orcompetition.

【 授权许可】

Unknown