by Dr. Gary Rosenberg
- What is a Mollusk?
- Molluscan classes
- Naming Names
- Establishing Relationships
- Origins of Diversity
- Classification of the Mollusca
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 become paralectotypes.
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.
- Kingdom Animalia
- Phylum Mollusca
- Class Gastropoda
- Order Caenogastropoda
- Suborder Neotaenioglossa
- Infraorder Discopoda
- Superfamily Tonnoidea
- Family Ranellidae
- Subfamily Charoniinae
- Tribe Charoniini
- Genus Charonia
- Subgenus (Charonia)
- Species tritonis
- Subspecies variegata
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 for places.
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 abbreviatusDautzenberg, 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.