Ediacaran Fossils: Metazoan Origins in the Proterozoic Geology 331, Paleontology The Doushantuo microfossils from China, 600 Ma Diploblastic Animals: Triploblastic Animals: Two Tissue Layers Three Tissue Layers Mesoderm in blue (jelly) Life of the Ediacaran, 543-600 Ma The White Sea assemblage, 560-550 Ma Ediacara Hills of Australia Ediacaran fossils exposed in sandstone. How were they preserved? A fossil sea pen from the Ediacaran of Australia. Ediacaran fossils were preserved as impressions in gelatinous microbial mats on the sea floor. Modern sea pens, relatives of corals Mawsonites, a fossil jellyfish? A variety of Ediacaran fossils Dickinsonia – a segmented worm Kimberella – a probable mollusc Spriggina – an arthropod? Tribrachidium – what is it? Arkarua – oldest echinoderm? Rangeomorphs from Newfoundland Aspidella from Newfoundland Charnia Charniodiscus Cloudina Namacalathus Calcified organisms at the end of the reconstructed Ediacaran 3D Trace fossils at the Ediacaran-Cambrian boundary: evidence of triploblastic animals Treptichnus pedum 3D Trace fossils at the Ediacaran-Cambrian boundary: evidence of triploblastic animals Treptichnus pedum Typical 2D traces made by diploblasts. Ediacaran of Newfoundland (Mistaken Point Fm.) A major ice age, the Marinoan (Snowball Earth) preceded the Ediacaran. How did this affect animal evolution? Equatorial Marinoan diamictites and cap carbonates in Namibia Calcite crystal fans in a Cap Carbonate grew out of the sea floor, indicating high levels of atmospheric CO2 had weathered silicate rocks on land producing calcium carbonate in the oceans. Alan J. Kaufman Nature 450, 807-808(6 December 2007) The Cryogenian Period – Snowball Earth What role did it play in the evolution of metazoans? • The Cryogenian (Greek: cryos "cold" and genesis "birth") Period: 850–635 Ma • Somehow, we went from this… • To this… Snowball Earth! .