﻿CANYON 
  FERRY 
  FOSSIL 
  VERTEBRATES 
  — 
  WHITE 
  435 
  

  

  In 
  summary, 
  the 
  available 
  data 
  show 
  that 
  there 
  was 
  environmental 
  

   (and, 
  in 
  a 
  sense, 
  climatic) 
  zoning 
  between 
  the 
  mountains 
  and 
  the 
  

   plains 
  in 
  Lower 
  Oligocene 
  times. 
  The 
  faunal 
  differences 
  embrace 
  

   larger 
  systematic 
  categories 
  (Felidae 
  and 
  Entelodontidae) 
  than 
  the 
  

   same 
  areas 
  do 
  today 
  (before 
  civilization 
  changed 
  the 
  picture). 
  Both 
  

   the 
  immigrants 
  and 
  the 
  indigenous 
  faunas 
  exhibit 
  nearly 
  the 
  same 
  

   degree 
  of 
  difference. 
  The 
  only 
  change 
  from 
  Lower 
  to 
  Middle 
  Oligocene 
  

   was 
  that 
  the 
  mountain 
  forms 
  were 
  able 
  to 
  invade 
  the 
  plains 
  and 
  most 
  

   of 
  these 
  were 
  immigrants. 
  None 
  of 
  the 
  plains 
  forms 
  were 
  successful 
  in 
  

   invading 
  the 
  moimtains 
  between 
  Lower 
  and 
  Middle 
  Oligocene 
  times. 
  

  

  References 
  

  

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