Paleozoic Era Invertebrates

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Paleozoic Era Invertebrates

• Chapter 12 Part 1

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Paleozoic Geology

• 4 transgressions
• Major orogenies
• Mountain ranges form/oceans close open
• Pangaea forms

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Pre-Paleozoic life

• Stromatolites
• Ediacaran fauna

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End of the Paleozoic life
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Cambrian climate

• What is the climate like coming out of the
  Proterozoic?
• Where are most of the continents located?

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Cambrian

• Animals with skeletons appear, abruptly
• Cambrian explosion
• Why?

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Early Cambrian fossils

• Shelly fauna
• Several millimeters

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Why develop a calcium skeleton in the Cambrian?

• Precambrian oceans low in calcium carbonate
  (calcite)
• Theory now rejected
• How to disprove?

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Why develop a calcium skeleton in the Cambrian?

• Metabolic systems evolving
• Organism needs to eliminate mineral matter
• Secret excess ions as skeleton

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Why develop an exoskeleton?

• Advantages?

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Cambrian predator and prey

• Anomalocaris and trilobite

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Marine communities

• How things get around
• Where they live
• How they feed

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Where marine animals live/how they move

• Organisms live above seafloor are pelagic
• Plankton are floaters
• Nekton are swimmers

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Where marine animals live/how they move

• Organisms live above seafloor are pelagic
• Plankton are floaters
• Nekton are swimmers
• Animal plankton zooplankton
• Plant plankton phytoplankton

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Where they live/how they move

• Organisms live in/on seafloor are benthonic
• Infauna (live in sediment)
• Epifauna (animals)
• Epiflora (plants)
• Can be sessile (stationary)
• Or mobile

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Feeding style

• Suspension feeders catch food from water
  (plants, animals, nutrients)
• Sediment-deposit feeders ingest sediment
• Herbivores plant eaters
• Carnivore/scavenger meat eaters

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Description

• Benthonic, epifaunal, suspension feeder
• Animal lives on seafloor and removes food from
  water

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Cambrian marine community

• Cambrian explosion
• Experimentation!

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Famous Cambrian fossil locations

• Burgess Shale, British Columbia
• Sauk Sea transgressing

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• Sands covered with black mud
• Shale preserved benthonic, soft-bodied community

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Why there?

• Avalanche of mud off edge of coast trapped
  shallow-water creatures
• Fine mud let soft-bodies be preserved

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Trilobites

• Appear in the Cambrian
• Benthonic, mobile, sediment-deposit feeders

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Trilobites

• Member of arthropod phylum
• Exoskeleton
• Distinct parts to body
• Jointed appendages

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Trilobites

• Member of arthropod phylum
• Exoskeleton
• Distinct parts to body
• Jointed appendages

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Trilobites

• Max diversity by Late Cambrian

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Trilobites

• Extinction at end of Cambrian
• Increased competition?
• Increased predation?
• Loss of habitat?
• Cooling seas?

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Cambrian Brachiopods

• Two-shelled animals
• Benthonic, sessile, suspension feeders
• Inarticulate muscles held shells together

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Inarticulate Brachiopod

• Two-shelled animals
• Benthonic, sessile, suspension feeders
• Inarticulate muscles held shells together

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Cambrian Archaeocyathid

• Benthonic, sessile, suspension feeders
• Built reef-like structures

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Cambrian Archaeocyathid

• Benthonic, sessile, suspension feeders
• Built reef-like structures

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Other fauna

• Arthropod from Burgess shale

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Other fauna

• Short-lived evolutionary experiments
• Anomalocaris
• Up to 3 feet long
• Major predator

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Other fauna

• Short-lived evolutionary experiments
• Helicoplacus extinct 20 Ma after appeared

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Marella, lt 1 inch
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Halluciginia
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Arthropod-like creature
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Cambrianscaly slug
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Paleozoic life

• Cambrian Explosion
• Exoskeleton
• Experimentation
• Animals to know
• Trilobite
• Brachiopod
• Archaeocyathid