EESC1180 Lecture Notes - Lecture 17: Ordovician Radiation, Ordovician, Small Shelly Fauna
21 Dec 2017
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Document Summary
Lived in the oceans millions of years ago. Aspidella: parts of organisms that attached to seafloor holdfasts . Burgess shale biota: locations show movement, fossil bearing unit. From deep water with very little oxygen, began greywacke. Pikaia: in the shale, earliest form of humans. Brought down to the bottom of deep shale thanks to a turbidity current. Pyrite was found with these fossils so we know the fossils were transported way deep down. Many didn"t have hard parts - very hard to preserve. Illustrates bias in fossil records toward animals with hard skeletons - shows that it doesn"t mean everything was hard shelled. Over 20 fossils need to be reclassified into their own phyla. Evolved to become bigger and bigger overtime. Bottom dwelling forms begin to create scratch marks - trace fossils. Most fossils appeared during cambrian explosion and then went extinct during ordovician silurian event. Appeared during great ordovician biodiversification event and went extinct during the permian triassic event.
