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The earliest known fossil actinopterygian is " Andreolepis hedei " , dating back 420 " million years ( Late Silurian ) .
 location: Silurian
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Silurian 
Answer:
 location: Silurian