Ediacarans, Small Shells and the Dawn of the Phanerozoic

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Ediacarans, Small Shells and the Dawn of the
Phanerozoic
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Edicaran Biota

• First fossils of multicellular organisms
• Some controversy
• Multicellular life?
• Colonies of single cells?
• Definitely not single cells
• Signs of tissue differentiation
• Advanced symmetry

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Ediacaran (Vendozoan)Biota
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Taphonomy of theEdicaran Biota

• Soft/firm bodied?
• Molds and casts in coarse sandstone
• Facies preference?
• Taphonomic bias?

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Radial and Bilateral Symmetry
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Radial Symmetry
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Bilateral Symmetry and Differentiated Structures
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Symmetry and Diversity
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Filter Feeders?
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Differentiated Structures, But Which End Was Up?
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Significant Diversity or Variations on a Single
Theme?
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Dawn of the Phanerozoic Small Shelly Fauna and
Trilobites
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What Do We Choose as the Start of the Cambrian?

• Extinction of the Ediacarans?
• First appearance of the small shelly fauna?
• Late Proterozoic
• First trilobites? Part of Cambrian Explosion
• Lower, but not lowest Cambrian
• First trace fossils of trilobites?
• First evidence of mobility (burrows)?
• First burrows chosen