The Collaborative International Dictionary of English v.0.48:

Antecessor \An`te*ces"sor\, n. [L., fr. antecedere, antecessum.
   See Antecede, Ancestor.]
   1. One who goes before; a predecessor.
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            The successor seldom prosecuting his antecessor's
            devices.                              --Sir E.
                                                  Sandys.
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   2. An ancestor; a progenitor. [Obs.]
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