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 Main Menu > GeoGallery > Rocks > Sedimentary > Shale with graptolites 
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Shale with graptolites Tetragraptus approximatis, Ordovician Period. What time is it? If you found one this index fossil in a rock, you'd know. Each animal was once widespread but quickly became extinct. Only a small percentage of fossils meet these criteria.
Group: Sedimentary |
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