ProtoceratopsZuniceratopsTuranoceratopsAvaceratopsEiniosaurusAchelousaurusPachyrhinosaurusCentrosaurusStyracosaurusAnchiceratopsArrhinoceratopsTriceratopsDiceratopsTorosaurusChasmosaurusPentaceratopsOsteologyMaximum ParsimonyBased on reanalysis of the original matrix.Farke_etal_2009a