ProtoceratopsZuniceratopsAvaceratopsEiniosaurusAchelousaurusPachyrhinosaurusCentrosaurusStyracosaurusAnchiceratopsArrhinoceratopsTriceratopsEotriceratopsDiceratopsTorosaurusChasmosaurusPentaceratopsOsteologyMaximum ParsimonyBased on reanalysis of the original matrix.Wu_etal_2007a