Article 51.1.
A legitimate name must not be rejected merely because it, or its epithet, is inappropriate or disagreeable, or because another is preferable or better known (but see Art. 56.1), or because it has lost its original meaning.
Example:
Watznaueria angustoralis Reinhardt, 1964 not be rejected in favour of invalid but better known Tremalithus barnesiae Black, 1959 [Invalid ICN, Art. 35.1]
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Article 6.4.
An illegitimate name is one that is designated as such in Art. 18.3, 19.6, or 52–54 (see also Art. 21 Note 1 and Art. 24 Note 2). A name that according to this Code was illegitimate when published cannot become legitimate later unless Art. 18.3 or 19.6 so provide or unless it is conserved or sanctioned.
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Article 11.2.
A name has no priority outside the rank in which it is published (but see Art. 53.4).
Example:
Species Cyclococcolithus astroporus Stradner, 1963 has priority over the subspecies Cyclococcolithus leptoporus inversus Deflandre in Deflandre &Fert, 1954
Species Helicosphaera truncata Bramlette & Wilcoxon, 1967 has priority over the subspecies Helicosphaera seminulum recta Haq, 1966 [if considered synonyms]
Because Cyclococcolithus astroporus and Helicosphaera truncata were published before the above subspecies were amended into species ranks
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Article 12.1.
A name of a taxon has no status under this Code unless it is validly published (see Art. 6.3, but see Art. 14.15).
If the species is invalid when published can not be amended because the invalid species has no statute under ICN.
Loeblich & Tappan (1966) states, "According to ICZN, an available name satisfies the rule; the valid name of a taxon is the oldest available name applied to it. The equivalent terms in the ICBN (=ICN) are legitimate and correct, respectively."
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Holotype
Article 9.1. A holotype of a name of a species or infraspecific taxon is the one specimen or illustration (but see Art. 40.4) used by the author, or designated by the author as the nomenclatural type. As long as the holotype is extant, it fixes the application of the name concerned (but see Art. 9.15).
Note 1: If the author used only one element, it must be accepted as the holotype.
Article 40.1. Publication on or after 1 January 1958 of the name of a new taxon of the rank of genus or below is valid only when the type of the name is indicated (see Art. 7-10; but see Art. H9 Note 1for the names of certain hybrids).
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Lectotype
Article 9.2. A lectotype is a specimen or illustration designated from the original material as the nomenclatural type, in conformity with Art. 9.11 and 9.12, if no holotype was indicated at the time of publication, or if the holotype is missing, or if a type is found to belong to more than one taxon (see also Art. 9.14). For sanctioned names, a lectotype may be selected from among elements associated with either or both the protologue and the sanctioning treatment (Art. 9.10).
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Conditions for the designation of lectotype can be summarised as below:
1. illustration from the original material as the nomenclatural type
Only original slide or sample is acceptable for "original material". The type area or the type section can not be satisfactory for "original material" designation. They may contain multiple stratigraphic levels / different nannofossil assemblages.
2. if no holotype was indicated at the time of publication
The lectotype can only be designated for the species published before 1 January 1958 if no holotype was indicated at the original publication.
After 1 January 1958, if no holotype was indicated at the original publication, that species is invalid and has no place in ICN (Art. 12.1).
Example: Cribrosphaerella danica Brotzen, 1959
3. if the holotype is missing
This is not applicable for nannofossils because the holotypes photos of all the nannofossils published are publicly available.
4. if a type is found to belong to more than one taxon
This is the only genuine reason for the designation of a lectotype for post 1 January 1958 publications.
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Definition of Terms in ICN
Diagnosis: A statement of that which in the opinion of its author distinguishes a taxon from other taxa (Art. 38.2); a diagnosis (or a description) is required for valid publication of a name (Art.38.1(a)).
Designation: [Not defined] – the term used for what appears to be a name but that (1) has not been validly published and hence is not a name in the sense of the Code (Art. 6.3 and 46.4) or (2) is not to be regarded as a name (Art. 20.4, 23.4, and 23.6).
Final epithet: The last epithet in sequence in any particular combination, whether in the rank of a subdivision of a genus, or of a species, or of an infraspecific taxon (Art. 11.4 footnotes).
Holotype: The one specimen or illustration used by the author, or designated by the author as the nomenclatural type (Art. 9.1).
Lectotype: A specimen or illustration designated from the original material as the nomenclatural type if no holotype was indicated at the time of publication, or if the holotype is missing, or if a type is found to belong to more than one taxon (Art.9.2).
Name: A name that has been validly published, whether it is legitimate or illegitimate (Art. 6.3) (see also designation).
Specimen: A gathering, or part of a gathering, of a single species or infraspecific taxon made at one time, disregarding admixtures, mounted either as a single preparation or as more than one preparation with the parts clearly labelled as being part of the same specimen (Art. 8.2 and 8.3).
Taxon (Taxa): A taxonomic group at any rank (Art. 1.1).
Validly published: Effectively published and in accordance with Art. 32-45 or H.9 (Art. 6.2) (see designation, name).