Section 8. Illegitimate Names and Epithets: Replacement, Rejection, and Conservation of Names and Epithets

A name contrary to a Rule is illegitimate and may not be used. However, a name of a taxon which is illegitimate when the taxon is in one taxonomic position is not necessarily illegitimate when the taxon is in another taxonomic position.

Example: If the genus Diplococcus Weichselbaum 1886 is combined with the genus Streptococcus Rosenbach 1884, Diplococcus is illegitimate as the name of the combined genus because it is not the earlier name. If the genus Diplococcus Weichselbaum is accepted as separate and distinct, then the name Diplococcus is legitimate.

If the taxon to which the name was applied, as circumscribed by the author, included the nomenclatural type of a name which the author ought to have adopted under one or more of the Rules.
Example: If an author circumscribes a genus to include Bacillus subtilis, the type species of the genus Bacillus, then the circumscribed genus must be named Bacillus.
If the author did not adopt for a binary or ternary combination the earliest legitimate generic name, specific epithet, or subspecific epithet available for the taxon with its particular circumscription, position, and rank.
Example: The name Bacillus whitmori Bergey et al. 1930 was illegitimate as Whitmore had named the organism Bacillus pseudomallei in 1913.
If its specific epithet must be rejected under Rules 52 or 53.
If it is a junior homonym of a name of a taxon of bacteria, fungi, algae, protozoa, or viruses.
Example: Phytomonas Donovan 1909, a genus of flagellates, antedates Phytomonas Bergey et al 1923, a genus of bacteria (Opinion 14).

Names of bacteria validly published under this revision of the Code are not to be rejected as homonyms of names of bacteria published before 1980 and omitted from the Approved Lists.

A word or phrase which is not intended as a specific epithet.
Example: Bacillus nova species Matzuschita.
A word which is merely an ordinal adjective used for enumeration.
Example: primus, secundus.
A number or letter
Example: a in Bacillusa von Freudenreich.

An epithet is illegitimate if it duplicates a specific or subspecific epithet previously validly published for a species or subspecies of the same genus but which is a different bacterium whose name is based upon another type.

Example: Corynebacterium helvolum (Zimmermann 1890) Kisskalt and Berend 1918 is based on the type of Bacillus helvolus Zimmermann 1890; the specific epithet helvolum cannot be used for Corynebacterium helvolum Jensen 1934, which is a different bacterium whose name is based upon another type.

A name or epithet illegitimate according to Rules 51b, 53, or 56a is replaced by the oldest legitimate name or epithet in a binary or ternary combination which in the new position will be in accordance with the Rules.

If no legitimate name or epithet exists, one must be chosen. Since a specific epithet is not rendered illegitimate by publication in a species name in which the generic name is illegitimate (Rule 32b), an author may use such an epithet if he wishes, provided that there is no obstacle to its employment in the new position or sense; the resultant combination is treated as a new name and is to be ascribed to the author of the combination. The epithet is, however, ascribed to the original author.

Example: Pfeifferella pseudomattei (Whitmore 1913) Ford 1928 is an illegitimate combination since Pfeifferella is a homonym of a protozoan generic name (Opinion 14). The epithet pseudomallei can be used for this organism in another genus, Pseudomonas pseudomallei (Whitmore 1913) Haynes 1957.

A legitimate name or epithet may not be replaced merely because of the following.

It is inappropriate.
Example: Bacteroides melaninogenicum (does not produce melanin; see J. Gen. Microbiol. 1:109120 [1947]).
It is disagreeable.
Example: Miyagawanella lymphogranulomatis.
Another name is preferable.
Example: Not yet found.
Another name is better known.
Example: Corynebacterium pseudodiphtheriticum cannot be rejected because the synonym Corynebacterium hofmannii is better known.
It no longer describes the organism.
Example: Haemophilus influenzae (does not cause influenza).
It has been cited incorrectly; an incorrect citation can be rectified by a later author.
Example: Proteus morganii Yale 1939 (see Lessel, E. E, IJSB 21:5557 [1971]).

Only the Judicial Commission can place names on the list of rejected names (nomina rejicienda) (see Rule 23a, Note 4, and Appendix 4). A name may be placed on this list for various reasons, including the following.

An ambiguous name (nomen ambiguum), i.e., a name which has been used with different meanings and thus has become a source of error.
Example: Aerobacter Beijerinck 1900 (Opinion 46).
A doubtful name (nomen dubium), i.e., a name whose application is uncertain.
Example: Leuconostoc citrovorum (Opinion 45).
A name causing confusion (nomen confusum), i.e., a name based upon a mixed culture.
Example: Malleomyces Hallier 1870.
A perplexing name (nomen perplexum), a name whose application is known but which causes uncertainty in bacteriology (see Rule 57c).
Example: Bacillus limnophilus Bredemann and Stürck in Stürck 1935 (Greek-Greek, marsh loving) and Bacillus limophilus Migula 1900 (Latin-Greek, mud loving); see Index Bergeyana, p. 196.
A perilous name (nomen periculosum), i.e., a name whose application is likely to lead to accidents endangering health or life or both or of serious economic consequences.
Example: Yersinia pseudotuberculosis subsp. pestis (Opinion 60) is to be rejected as a nomen periculosum.

Note 1. This application is restricted to a proposed change in the specific epithet of a nomenspecies which is widely recognized as contagious, virulent, or highly toxigenic, for example, to that of a subspecies of a species having a different host range or a degree of contagiousness or virulence. If the Judicial Commission recognizes a high order of risk to health, or of serious economic consequences, an Opinion may be issued that the taxon be maintained as a separate nomenspecies, without prejudice to the recognition or acceptance of its genetic relatedness to another taxon.

A conserved name (nomen conservandum) is a name which must be used instead of all earlier synonyms and homonyms.

Note 1. A conserved name (nomen conservandum) is conserved against all other names for the taxon, whether these are cited in the corresponding list of rejected names or not, so long as the taxon concerned is not united with another taxon bearing a legitimate name. In the event of union or reunion with another taxon, the earlier of the two competing names is adopted in accordance with Rules 23a, b.

Note 2. Only the Judicial Commission can place names on the list of conserved names (normina conservanda) (see also Rule 23a, Note 4, and Appendix 4).