International Code of Phylogenetic Nomenclature (PhyloCode)

Division II. Rules

Chapter III. Names

Article 6. Categories of Names


Established clade names are those that are published in accordance with Article 7 of this code. Unless a clade name is established, it has no status under this code.

Recommendation 6.1A

In order to distinguish scientific names from other (e.g., vernacular) names, all scientific names should be italicized when they appear in print.

Note 6.1A.1

Italicizing all scientific names is consistent with the 2018 edition of the ICNAFP but not with the 1999 edition of the ICZN.

Recommendation 6.1B

In order to indicate which clade names are established under this code and therefore have explicit phylogenetic definitions (and whose endings are not reflective of rank), it may be desirable to distinguish these names from supraspecific names governed by the rank-based codes, particularly when both are used in the same publication.

Example 1

The letter “P” (bracketed or in superscript) might be used to designate clade names governed by this code, and the letter “R” to designate names governed by the rank-based codes. Using this convention, the name “Ajugoideae[R]” would apply to a plant subfamily, which may or may not be a clade, whereas “Teucrioideae[P]” would apply to a clade, which may or may not be a subfamily.

Example 2

If the name Teucrioideae applied to both a clade (this code) and a subfamily (ICNAFP), they could be distinguished as “clade Teucrioideae” versus “subfamily Teucrioideae”.


Preexisting names are scientific names that, prior to their establishment under this code, were either: (a) “legitimate” (ICNAFP, ICNP), “potentially valid” (ICZN), or “valid” (ICVCN); or (b) in use but whose application to taxa is not governed by any code (e.g., unranked names and zoological names ranked above superfamily). In addition, scientific names governed by the ICNAFP that are in current or recent use but have never been published with a Latin description or diagnosis (and therefore violate ICNAFP Article 39 if published between 1935 and 2011) are considered under this code to be preexisting names, provided that they have been published with a description or diagnosis in some other language and otherwise qualify as legitimate names under the ICNAFP.

Note 6.2.1

Names that were phylogenetically defined in publications (Art. 4) prior to the starting date of this code (Art. 7.1) and are not “legitimate” (ICNAFP, ICNP), “potentially valid” (ICZN), or “valid” (ICVCN) are considered to be preexisting names after the starting date of this code. They fall under Article 6.2(b) because they are in use but were not governed by any code at the time they were published.


Converted names are preexisting names that have been established as clade names in accordance with the rules of this code.


An acceptable clade name is one that is in accordance with the rules of this code; that is, it is both (a) established and (b) not a non-conserved (Art. 15) later homonym.


The accepted name of a clade is the name that must be adopted for it under this code. It must (1) be established (Art. 7), (2) have precedence (Arts. 12–15) over alternative uses of the same name (homonyms) and alternative names for the same clade (synonyms), and (3) not be rendered inapplicable by a qualifying clause in the context of a particular phylogenetic hypothesis (Art. 11.12).


Once a clade name has been established, its status as an acceptable and/or accepted name is not affected by inaccurate or misleading connotations; thus, a name is not to be rejected because of a claim that it denotes a character, distribution, or relationship not possessed by the clade.