The Collaborative International Dictionary of English v.0.48:
Progenitor \Pro*gen"i*tor\, n. [OF. progeniteur, L. progenitor, fr. progignere, progenitum, to bring forth, to beget; pro forth + gignere to beget. See Gender kind.] An ancestor in the direct line; a forefather. [1913 Webster] And reverence thee their great progenitor. --Milton. [1913 Webster]WordNet (r) 3.0 (2006):
progenitor n 1: an ancestor in the direct line [syn: progenitor, primogenitor]