graptolites
- Created by: ameliacooper28
- Created on: 08-04-20 11:21
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- graptolites
- composed of schleroprotein which is resistant to decay
- planktonic - worldwide distribution
- facies free
- found in black shales - they'd die and sink to the bottom
- good zone fossils
- evolved rapidly and died quickly
- abundant
- absent from shallow water
- basic evolutionary trends throughout ordovician
- stipes change from many to few
- thecae become more spread out and complex
- stipes go from pendant (pointing down) to scandent (pointing up)
- thecae change from pointing inwards to outwards
- evolve: early Ordovician dominant: late Ordovician and early Silurian extinct: Devonian
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