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Species name complex

A species name complex is an entity that describes a group of species names that share the same etymology and grammatical behavior. For example, all species names based on the Latin adjective palustris form the palustris species name complex.

Species name complexes are primarily useful for determining whether and how species names need to be declined for gender, because species names that are Latin adjectives agree in grammatical gender with the genus name. Species name complexes also make it easier to understand the etymologies of names.

Fields

Species name complexes have the following fields:

Kinds of name complexes

Under Article 11.9.1, species names fall in one of five groups: (1) Latin adjectives, (2) Latin nouns in the nominative case, (3) Latin or Latinized nouns in the genitive case, (4) Latin adjectives in the genitive case, and (5) non-Latin words.

Latin adjectives

Latin and Latinized adjectives are a very common category of species names. Names in this group are the only ones that change form depending on the grammatical gender of the genus they are assigned to. Zoological nomenclature declines only Latin and Latinized adjectives; adjectives in other languages, even Greek, are treated as indeclinable (Art. 31.2.3).

There are two main groups of Latin adjectives, and several smaller ones:

Latin has many other groups of irregular adjectives, including some that are used in scientific names, such as alius, alia, aliud and celer, celeris, celere.

There is a special group of names of the form adjective-i-noun, where the noun is often a body part, like breviceps "short-headed". I believe that these names are adjectives, although many are indeclinable.

Nouns in apposition

Latin nouns in the nominative case are fairly common as scientific names. For example, typus "type" is common. The Code specifies (Art. 31.2.2) that names that could be either a noun or an adjective are to be treated as nouns unless there is evidence that the author intended them to be adjectives. This affects many names in -fer. These names are in the "noun in apposition" complex.

Genitive nouns

Latin nouns in the genitive case are often geographic names (e.g. italiae "of Italy"), which are included in the "genitive" complex. However, by far the most common group are patronyms, names formed from personal names. Patronyms in turn fall into two subgroups. Latin and Latinized names use the proper Latin genitive form, which will frequently be a suffix of -is or -i ("patronym latin"). Modern names are turned into patronyms by adding -i (for a man), -ae (for a woman), -orum (for multiple men or a mixed group), or -arum (for multiple women).

A few practical issues that arise are:

Genitive adjectives

Although the Code allows for species names formed from the genitive forms of Latin adjectives, the provision appears to be mostly intended for parasites. I have never encountered such names in tetrapods, but the few examples in the database are included in the "genitive adjective" complex.

Non-Latin words

A large proportion of species names are not based on Latin or Latinized words. These names are always indeclinable. They are in the "non-Latin" complex.