M_W_Chapter_21-1_Cambrian_Life_short_version

M_W_Chapter_21-1_Cambrian_Life_short_version - Paleozoic...

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Paleozoic Life recap latest Precambrian events : 1. Neoproterozoic glaciation (?snowball) 2. Ediacaran Fauna soft-bodied animals, probably ancestors to jellyfish and sea anemones (Hydrozoa) Earliest shells ( Cloudina ) followed by major extinction immediately before the Cambrian.
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Early Cambrian “Explosion of Life” A myth! Common impression that all groups of animal fossils suddenly appeared at very beginning of the Cambrian In fact the Cambrian started slowly and new groups of shelly fossils started to appear bit by bit Soft-bodied animals were probably common even in the late Precambrian
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Earliest Cambrian (“stage 1”) a few rare, small shelly fossils (SSF). skeletons of calcium carbonate, phosphate, even silica.
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Early Cambrian (“stage 2”) about 7 million years have passed. SSF (mostly < 1 cm) become common, particularly in Siberia. Some are now known to be parts of “chain-mail” covering of larger animals. Protection from predators? These rocks are called the Tommotian Stage.
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Early hard-shelled fossils  (mostly Tommotian – early Cambrian) Cloudina (latest Precambrian)
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Tommotian fossils Include: Archaeocyathids, (early reef-builders)
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M_W_Chapter_21-1_Cambrian_Life_short_version - Paleozoic...

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