33950
The first radiation of the diatoms ( generally siliceous shelled , rather than calcareous ) in the oceans occurred during the Cretaceous ; freshwater diatoms did not appear until the Miocene .
 Cretaceous, Miocene
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Cretaceous, Miocene