Article 44. Nominotypical taxa
When a genus is considered to contain subgenera, the subgenus that contains the type species of the nominal genus is denoted by the same name as the genus, with the same author and date [Art. 43.1]; this subgenus is termed the nominotypical subgenus.
If the name in use for a genus, and hence for its nominotypical subgenus, is unavailable or invalid it must be replaced by the name valid under Article 23.3.5; the subgenus containing the type species of the valid nominal genus and denoted by the valid name of the genus becomes the nominotypical subgenus.