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Louisiana State University
GEOL 1003

CHAPTER 13 EARLY PALEOZOIC CambrianOrdovician Periods Introduction to Cambrian and Ordovician oCambrian and Ordovician Periods are the OLDEST in the Paleozoic It was an era where Rocks became more conspicuous and animals emergedoCambrian Period whensealevel rose Sauk Transgression Grand CanyonPeriod of massive diversification of life Early Cambrian Explosion of lifeoOrdovician Period of high sealevelGlaciation caused massive global extinction and end to boom THE CAMBRIAN PERIOD Explosion of life oCambrian Life in the OceanCambrian is RICH in oceanic fossils bc life growth Cambrian fossils contain SKELETONS as opposed to soft bodied in precambrianTerrestrial system on earth was barren with NO insects or vertebratesSimple protists and fungi in Fresh water and simple fungi on landoTreptichnus Pedum is the index trace fossil at Baseof the Cambrian PeriodIt is an index or guide fossil because it is widespread and marks the beginning of the CambrianThe first occurrence of the Treptichnus Pedum is at Base of the Cambrian which coincides with the last of the Edicaran FaunaThis trace fossil shows a complex BRANCHING form of burrowing which indicates evolution from straight burrows in precambrianoSkeletons evolved in early Cambrian into 3 fauna groups1The Lowermost Cambrain Fauna oldestSmall tubeshaped or vaseshaped skeletons some contained small teeth 1The Tommatian Fauna from the central part of LowerCambrian middle that lasted 34 m yrsIncludes a host of small skeletal elements Some cannot be assigned to any living phylum and many just went extinctThe sponge and gastropodmollusk forms survived mostThis fauna suddenly disappearedreasons unknown 1Large Animals with Skeletons in the final million years in early Cambrian youngestTommotian Fauna were replaced by larger animals the most abundant wereaTRILOBITESaBrachiopodsaMollusksaEchinodermso several are represented by descendants of modern phylaTRILOBITES are most dominantabundant group in CambrianoThese are ARTHROPODS has many modern taxaoPossessed a calcifies segmented EXOSKELETON with unprotected underside o Mostly bottomdwelling deposit feeders and Lacked a strong mouthpart for chewingABRACHIOPOD fossils found in early Cambrianmodern phylumoBrachiopods used a lophophore to pump water and sift sieve foodoLingula is a modern brachiopod AMonoplacophoran MOLLUSKSmodern phylumoMonoplacophorans are abundant in early CambrianoGraze on bacterial and algaeAECHINODERMS modern phylumoAbundant in early Cambrian oSoftBody Animals appear in Early Cambrian as wellCHENGJIANG FAUNA are soft body Cambrian animals that includeJellyfished carnivores and other cnidariansSegmented wormsSoftbody arthropods most diversePredatory worms priapulidsAnomalocaridsHuge carnivores 2m long that resemble arthropods Swimmers in ocean who impale prey with sharp spinesoFew Modes of Life for Early Cambrian AnimalsEarly Cambrian animals were mainly ON or close to seafloor3 basic modes of animal life feeding1Deposit FeedersTrilobites arthropods echinodermsExtract organic matter from sediments1GrazersMonoplacophoran MollusksGraze on algae on seafloor like cyanobacteria mats etc1Suspension Feeders Brachiopods Sessile EchinodermsCollected organic matter from the waterBrachiopods and Sessile echinodermsEocrinoid with short stalks oOther Marine Life Modes in Early CambrianEarly Cambrian Zooplankton included Jelleyfish and few planktonic Trilobites
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