Hi all

When it comes to the use of a name for a particular taxon / species it can
have three possible states

i  - valid
ii  - available
iii  - invalid and therefore not available

Valid names are usually the first/earliest correctly published name say for
example Meridolum corneovirens (Pfeiffer, 1851)(Australian land snail) or
Cypraea trigis Linnaeus, 1758 (Tiger Cowry).

Available names are all names that have been introduced correctly
(according to the current nomenclatural rules)
For example names considered to be synonyms of Cypraea trigis include
Cypraea ambigua, Cypraea feminea, Cypraea flamma and Cypraea tigrina all by
Gmelin, 1791. These names are also available names for it maybe found in
the future that one or more of these names maybe valid and represent a
different species.

Invalid names are those names that were introduced but were not done
correctly for any number of reasons - mostly determined by the Rules of
Nomenclature and see Andrews post.

For example varietal or forma names published after about 1930 have no
taxonomic standing, so if I were to introduce a new cowrie this year say :
Cypraea trigis variety alba  or Cypraea trigis forma alba or Cypraea tigris
schilderiana forma alba or Cypraea tigris schilderiana alba then all these
names would be taxonomically invalid even if holotypes etc were designated
and are therefore unavailable. These types of names are common in the no
longer published journal (I think) World Shells. An example of a real
invalidly published name is Umbilica (Umbilica) armeniaca var southstralica
Raybaudi, 1980.

An example of a varietal name that would be considered valid under the
current rules is the following:
Helix mabillei var minor Crosse, 1864 (an Australian land snail) is an
available name, it becomes today Helix mabillei minor Crosse, 1864 if as is
the case for this particular name the specimen is a different species from
Helix mabillei Crosse, 1864 it would become Helix minor Crosse, 1864.

I hope this makes the concepts a little more understandable using some
actual examples.

Stephanie



******************************************************************************
Stephanie A. Clark

Biodiversity & Systematics
Department of Biological Sciences
University of Alabama
Box 870345
Tuscaloosa, AL  35487
Phone: 205-348-5828 FAX: 205-348-6460
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