by Dr. Gary Rosenberg
The practice of giving species a two-part name composed of a
generic and a specific name started with Carl von Linné
in 1758, when he published the tenth edition of Systema Naturae.
Previously there had been no clear-cut distinction between the
name of a species and its description. Species names are based
on type specimens. These are the specimens an
author used in describing a particular species. A single specimen,
the holotype, is chosen by the author to represent
the species; his other specimens are paratypes.
If the original author did not chose a holotype, his specimens
are called syntypes. A later author can designate
what is called a lectotype from the syntypes. The lectotype
serves the same function as the holotype and the other syntypes
Generic names are based on a
type species, designated by the original author
or a later worker. Familial names must be formed from the root
word of their type genus. There is a hierarchy
of names ranging from kingdom to subspecies exemplified here
for Charonia tritonis variegata, the Atlantic Triton's Trumpet.
Ranks in addition to these are
possible, such as subclass, superorder, subtribe, and are used
as necessary to specify relationships.
Various rules apply to the formation
of some of these names. Superfamily names must end in "-oidea"
or "-acea," but -oidea is now preferred. Family names
end in -idae, subfamily names in -inae, and tribe names in -ini.
If the specific name of a species
is an adjective, it must agree with the gender of the genus
it is combined with. Specific names that are nouns do not change
endings. Most specific names are Latin or are treated as Latin.
The two most common kinds of Latin adjectives have the endings
-us, -a, -um and -is, -is, -e for masculine, feminine, and neuter
respectively. The endings -i, -ae, -orum, or -arum are used
for species named after a man, woman, men, or women, respectively.
The ending -ensis (or -ense) is often used for species named
The gender of a genus must be
determined from a Latin dictionary, or by the manner in which
the original author used it if it is not a Latin (or Greek)
word. Beware -- a genus ending in -us is not necessarily masculine,
nor is -a necessarily feminine. As an example, Cyphoma is neuter,
so Cyphoma gibbosum (rather than "gibbosa" is correct.
If a species is changed from one genus to another, its ending
might change. Cyphoma gibbosum was originally named Bulla gibbosa
by Linné in 1758. The ending changed to -um when the
species was assigned to the genus Cyphoma.
The author and date of description
are not part of the species name, but are often cited with it:
Bulla gibbosa Linné, 1758. If the species is no longer
placed in the genus that it was named in, the author and date
are placed in parentheses: Cyphoma gibbosum (Linné, 1758).
Specifying the author and date prevents confusion if the same
specific name has been used twice to refer to different species
in the same genus. For example, Conus abbreviatus Reeve, 1843
is a valid species, but Conus abbreviatus Dautzenberg, 1937
is a variety of Conus textile. Identical species names such
as these are called homonyms and only the older
name can be used. Similarly, if a species (or genus or family)
has been given two different names, the names are synonyms
and only the older one can be used (unless the older one is
a homonym of a still older name).
The rules of nomenclature are
codified in the International Code of Zoological Nomenclature
(3rd edition) published by the International Commission on Zoological
Nomenclature in 1985. The purpose of these rules is to ensure
that the names given to groups of animals are unique and therefore
unambiguous. (Other groups of organisms, such as plants and
bacteria, have their own codes of nomenclature.)
The above material
has been adapted from Dr. Rosenberg's The Encyclopedia of Seashells,
published by Robert Halt, Ltd., London, 1992.