The Collaborative International Dictionary of English v.0.48:

Monophyletic \Mon`o*phy*let"ic\, a. [Gr. ? of one tribe, fr.
   mo`nos single + ? clan.] (Biol.)
   Of or pertaining to a single family or stock, or to
   development from a single common parent form; -- opposed to
   polyphyletic; as, monophyletic origin.
   [1913 Webster]