Synonym (taxonomy)

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In biological nomenclature , the term synonym is used when different scientific names refer to the same taxon . The use and more precise terminology of the term are different in zoology and botany .

In biological nomenclature , the priority rule applies , according to which of several published names for the same taxon, as a rule, the first published, i.e. H. the oldest name should be used. The main source of synonyms is when later taxonomists describe the same group again under a new name. This can have various reasons: The original description was possibly vague, it was unknown to the new editor (e.g. published in a very old, a little respected and widespread or a foreign-language specialist journal), or the edited group has not been the subject of a long time a taxonomic revision or monograph , which makes the specialist literature difficult to survey. Another important reason is the lack of a global overview, so that widespread species are described multiple times in different regions (for example, species that are common in Europe and North America). Different taxonomic concepts also play a role (cf. Lumper and Splitter ). If a synonym is noticed in a taxonomic paper, the younger name is synonymous with the older one. In species indexes and revisions, a list of known synonyms is usually added after each species name. These names should no longer be used once the synonymy has been recognized. Occasionally it happens that an older name, taken as a synonym, is later taken as valid again. This often happens when, during a revision, what was previously considered one type is broken down into several types. It is possible that one of the newly recognized species was given a name earlier. This is then the valid name of the newly recognized taxon, even if this difference was actually unknown to the person who first described it at the time.

According to an estimate in 2013, around 20 percent of the species names described (at that time) are still undiscovered synonyms. This value differs depending on the taxonomic group. Of course, some of the newly described species will later prove to be synonymous.


In zoological nomenclature synonyms are different names that designate the same taxon , for example two names for the same species. As a rule, the older synonym (“senior synonym”) is used; the younger one (“junior synonym”) is only used in exceptional cases, for example when the older one is suppressed or because the older name was previously given to a completely different animal.

In order to be considered a synonym, a name in zoology must be published correctly in accordance with the rules . Manuscript names and names mentioned without any description ( nomina nuda ) cannot be synonyms.

Objective synonyms

Objective synonyms definitely refer to the same taxon because they are based on the same type specimen .

Objective synonyms often appear in genres that have the same type species for different reasons. Often it was not known that a generic name already existed, or the new generic name was nevertheless deemed necessary. An example is the genus Pomatia Beck, introduced in 1837 for a group of land snails, including the Roman snail Helix pomatia as a type species . However, Helix pomatia was already the type species of the genus Helix Linnaeus, 1758, so Pomatia is an objective synonym for Helix . Helix is also an objective synonym for Pomatia - but it is older and therefore has priority over the younger name Pomatia due to the priority rule .

At the species level, there are rarely objective synonyms and they are hardly known. A species only has an objective synonym if two names actually refer to exactly the same type specimen. Even if one of the two names has two types of type, there is no longer any objective synonymy (unless there is a special case where the second name was expressly suggested as a replacement name for the first). Often in old literature there are sentences like "I call this species x, that is the same species that the previous author called y". This alone says nothing about an objective synonymy as long as the author has not written anything explicitly about the underlying type specimens.

Subjective synonyms

In the case of subjective synonyms, there is room for discussion because they are based on different types, which can also belong to different types.

Subjective synonyms are very common, simply because in the past many variations were described as separate species, which are now counted as a single species. Most of the species names introduced in the last 250 years are subjective synonyms of other species names.


In botanical nomenclature, the synonym of a botanical name is also a name that refers to the same taxon.

In botany, unpublished or manuscript names can also be used as synonyms.

Homotypical synonyms

A homotypical or nomenclatory synonym exists if the same type specimen is used.

The name Leontodon taraxacum L. (a dandelion ) is based on the same type specimen as Taraxacum officinale F.H.Wigg . So both are homotypical synonyms. Another example: The name Pinus abies L. for the common spruce has the same type specimen as Picea abies (L.) H. Karst . When the latter is used as the correct name (which it most often does), Pinus abies is a homotypical synonym of Picea abies . However, if it were the other way around, Pinus abies would be the name used and Picea abies would be a homotypical synonym for Pinus abies .

For botany, a name that is in a different genus is a different name in the sense of synonymy. In contrast to zoology, it also has its own author (namely the name of the person who first placed the species in the other genus).

Heterotypic synonyms

A heterotypic or taxonomic synonym exists when two different type specimens are used.

Some botanists split the dandelion into many separate species, each with its own name. If the dandelion is viewed as a single species, then the names for the individual forms are heterotypic synonyms of Taraxacum officinale F.H.Wigg .

Comparison of zoology and botany

  • The homotypical (nomenclature) synonyms in botany are objective synonyms in zoology.
  • The heterotypic (taxonomic) synonyms in botany are subjective synonyms in zoology.
  • The same species name in another genus is synonymous in botany and has an additional author. In zoology it is not a synonym, but just a different genus-species combination and has no additional author.
  • In botany an unpublished name can also be a synonym, but not in zoology.


  • RA Blackwelder: Taxonomy: A text and reference book . Wiley, New York 1966.

Web links

Individual evidence

  1. ^ Mark J. Costello, Robert M. May, Nigel E. Stork (2013): Can We Name Earth's Species Before They Go Extinct? Science 339: 413-416. doi : 10.1126 / science.1230318
  2. ICZN Code 4th Edition (2000), Art. 61.3.3, 61.3.4
  3. p. 43 in Beck, H. 1837. Index molluscorum præsentis ævi musei principis augustissimi Christiani Frederici. - pp. 1-100 [1837], 101-124 [1838]. Hafniæ.
  4. ICZN Code 4th Edition (2000), Art. 61.3.1