Ediacarans, Small Shells and the Dawn of the Phanerozoic 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 Ediacaran (Vendozoan)Biota Taphonomy of the Edicaran Biota • Soft/firm bodied? • Molds and casts in coarse sandstone • Facies preference? • Taphonomic bias? Radial and Bilateral Symmetry Radial Symmetry Bilateral Symmetry and Differentiated Structures Symmetry and Diversity Filter Feeders? Differentiated Structures, But Which End Was Up? Significant Diversity or Variations on a Single Theme? Dawn of the Phanerozoic: Small Shelly Fauna and Trilobites 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