The Collaborative International Dictionary of English v.0.48:

Polygenetic \Pol`y*ge*net"ic\, a.
   1. Having many distinct sources; originating at various
      places or times.
      [1913 Webster]

   2. (Biol.) Of or pertaining to polygenesis; polyphyletic.
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   Polygenetic mountain range (Geol.), one which is composite,
      or consists of two or more monogenetic ranges, each having
      had its own history of development. --Dana.
      [1913 Webster]