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Suborder:
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Goniatitina 
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Superfamily:
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Dimorphoceratoidea 
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Family:
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Girtyoceratidae 
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Subfamily:
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Girtyoceratinae 
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Genus:
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Girtyoceras 
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Species:
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simplex | 
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Qualifier:
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ss | 
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Author:
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	Moore 1946,p.400	 
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Lower Boundary:
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Up.Visean  Goniatites BZ base [up.VIS], 333.5 million years
 
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| 
Upper Boundary:
 | 
DER Go alpha 2--Go alpha 3  [11.60], 332.3 million years
 
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