A synapomorphy is a homologous trait (or traits) shared by two or more taxa which were derived from a common ancestor. In cladistics, synapomorphies are used to establish phylogenies.

Shared characteristics that define a cladistic grouping. An apomorphy (derived or specialised character) shared by two or more groups which originated in their last common ancestor (from the Greek words apo = from and morphy = shape). Synapomorphy

Phylogenetics

Синапоморфия