The International Code of Zoological Nomenclature (ICZN) provides a universal set of rules and recommendations for naming animals. It ensures that every animal species has one correct and universally accepted scientific name. The ICZN promotes stability, clarity, and universality in animal names.
Objectives of ICZN: To standardize zoological names globally. To ensure stability and universality in naming. To avoid or resolve disputes regarding animal names. To promote clear communication among scientists internationally.
Goal: One species = One valid, internationally recognized name.
Principles of ICZN: The ICZN operates on several fundamental principles:
1. Principle of Binomial Nomenclature
Each species has a two-part name:
Genus name (Capitalized)
Species name (small letters)
Example: Homo sapiens
2. Principle of Priority: First validly published name takes precedence.
The earliest name (after 1758) is considered the correct and valid name.
Example: If two names are given for the same species, the one published first is accepted.
3. Principle of Typification: Each taxon must have a type specimen (holotype) that serves as a reference for its name.
Example: The type specimen of Panthera leo (lion) defines the species.
4. Principle of Homonymy: No two different taxa can bear the same name. If two taxa accidentally receive the same name (homonyms), the older name remains valid.
5. Principle of Coordination: When a taxon is described at a certain rank (say genus), corresponding names at other ranks (like subgenus) are automatically created.
Interpretation of ICZN: Flexibility: ICZN rules are interpreted to maintain stability and minimize confusion.
Commission’s Role: The International Commission on Zoological Nomenclature interprets and resolves disputes or complex cases.
Example: If a strict application of the rules would destabilize the usage of a well-known name, the Commission can make exceptions.
Application of Important Rules
Key Important Rules:
Names must be Latinized.
Names must be published in a recognized, permanent form.
Name must be available (properly described with type designation).
Abbreviations like “sp. nov.” (New species) or “gen. nov.” (New genus) must be used for newly described species or genera.
Gender agreement: Species names must agree in gender with genus names.
Correct spelling is essential; incorrect original spellings can sometimes be corrected.
Law of Priority: Among competing names for the same taxon, the oldest available name (earliest publication) is considered valid.
Applies only after 1758, the starting point of zoological nomenclature (10th edition of Linnaeus’ Systema Naturae).
Prevents confusion caused by multiple names for the same organism.
Example: If Felis leo was named in 1758 and Leo ferox was named in 1762 for the same species, Felis leo would be the valid name under the law of priority.
Validity of Names: A name is valid if: It was published properly. It follows all ICZN rules. It is the earliest available name. It is not suppressed by the Commission.
Invalid names are: Names published without proper description. Names that are junior synonyms (later names for the same species).
Homonyms (duplicate names for different taxa).
Unpublished names.
Summary Table
| Aspect | Description |
| Objective | Standardize, stabilize zoological names |
| Principles | Binomial nomenclature, priority, typification, homonymy, coordination |
| Interpretation | Flexibility by the ICZN to promote stability |
| Application | Clear rules for publishing, describing, and naming |
| Law of Priority | First valid name after 1758 must be accepted |
| Validity of Names | Depends on proper publication, priority, and compliance with rules |
Important Points to Remember
ICZN governs only animals, not plants or fungi (plants follow ICN).
1758 (Linnaeus’ Systema Naturae, 10th edition) is the official starting point for zoological names.
Type specimen is critical for linking a name to a real organism.
Stability of names is more important than strict application of rules in some cases.