def self.disjoint_taxon_name_classes
    self.parent.disjoint_taxon_name_classes +
        self.collect_descendants_and_itself_to_s(TaxonNameClassification::Iczn::Unavailable::Suppressed,
            TaxonNameClassification::Iczn::Unavailable::NomenNudum,
            TaxonNameClassification::Iczn::Unavailable::NonBinominal) +