apomorphy

In discussions of phylogeny or cladistics, a derived or advanced character state. Apomorphies shared by different taxa are termed synapomorphies (compare autapomorphy). Only synapomorphies whose origin can be traced back to a recent common ancestor (i.e. homologous character states) are of use in constructing phytogenies or cladograms. Analogous 'synapomorphies' may arise by convergent evolution and if identified as such are ignored. Compare plesiomorphy .