Rules of Nomenclature

Scientific nomenclature is not arbitrary, because then it would be unclear and mistakable. Also, in the standardized scientific nomenclature, the endings of most names give information about the hierarchic status of the systematic group they belong to. 

Systematic names up to the category of superfamily are subject to control by the International Commission for Zoological Nomenclature (ICZN). Especially for species, but also for other lower rank systematic categories, it is clearly regulated, how they should be named.

On the basis of the Linnaean binary nomenclature each species is to be labelled with the name of the genus it belongs to, as well as with the name of the species itself. The species' name is defined by the author who first published a description of the species in print. That is why usually next to the names of genus and species the author's name is given and the date of his publication. In many generally known species that publication is the basic book by Carl v. Linné, so to speak denoting the hour Zero of biological systematics. As Linné published his book under the Latinized version of his name, the complete scientific name of the Roman snail is Helix pomatia Linnaeus 1758. Authors' names in scientific publications usually are written in capitals or in small capitals. In contrary to that scientific names are to be written in italics.

The first author's name also remains, should the species be assigned to another genus. Should the systematic name of the group change as a consequence of new scientific discoveries, the author's name will be put between brackets. So for example, the malacologist O.F. Müller described the brown garden snail in 1774 as Helix aspersa. In the meantime the species has been renamed Cornu aspersum, to indicate its difference to snail species of the Helix genus, such as the Roman snail. This is why in complete systematic lists, the brown garden snail is stated as Cornu aspersum (O.F. Müller 1774) (see.: Identification of Roman snails and their relatives).

But even for the first author the name of a species he wishes to describe is not arbitrary. First the name intended for the species may not be preoccupied by another species. Should this happen anyway, a state called homonymy, there must be a decision, which name is older and therefore valid, so the younger name must be replaced by another. Also, a species intended for description must not be previously described by another author. A synonymy exists, if by chance an already described species is described another time. So in contrary to a homonymy, where one name describes two different species, in the case of a synonymy, one species is described by two names. Here as well the older name is the valid one and the younger one is to be replaced.

During the first publication of a species the author specifies, which sample of the described species is to be regarded as type and - importantly - in which museum it is to be stored. After some species have been merged after their first description, species with one type are called monotypic, in contrary to polytypic species with several types. If there is only one definite type for a species, then it is called a holotype ("whole" type). The author can, however, also present additional types apart from the main type, which are then called paratypes. If the author has not specified, which type is to be regarded as holotype, then all types are regarded as syntypes (collective types). If the holotype is lost, possibly from the paratypes, a so-called lectotype ("elected" type) or also a neotype ("new" type) can be chosen. The status of a sample must be specified in the first publication.

Genera are combined in a family by putting the name of the type genus in plural and adding the suffix -idae. So for example from the genus Helix the plural is Helices and so the family name is Helicidae. Correspondingly for a subfamily the ending -inae will be used etc.

Category Ending
Superfamily -oidea, -acea
Family -idae
Subfamily -inae
Tribus -ini

The endings of higher categories are also more or less defined, only here the Commission has no say, which is why apart from standardized names there are several older names not adjusted to the standard. This is often because groups of higher category were originally described as order or a comparable category, but had to be promoted or demoted following the development of systematics. In principle defined ending only exist for orders and suborders. Concerning orders, as well as suborders, there is the difference between the old school systematicians who use the long endings (-oina, -oida) and new school systematicians who following the Russian example omit the o and call groups -ina or -ida.

Category Ending
Order -oida, -ida
Suborder -oina, -ina, -inei

Sometimes there are bizarre excesses in nomenclature: There are few rules apart from those described on the present page. And so there are species like the cone shell Conus tribblei Walls 1977, named after the discoverer's cat, which again was named for the tribbles from Star Trek, and the grass snails Vallonia eiapopeia Gerber 1996 and Vallonia hoppla Gerber 1996 ("eiapopeia" is a German children's rhyme and "hoppla" means "oops").

Wikipedia: Liste skurriler wissenschaftlicher Namen aus Biologie und Medizin (In German).