Re: Taxonomy Question

[Jocelyn Falconnet <j.falconnet@gmail.com>]

Saint Abyssal a écrit :

> Is there a term that refers categorically to junior synonyms, nomena 
dubia, lapsus calami, and all the other situations that cause scientists 
to disregard genera and species? I've always called them "invalid taxa" 
but technically that only applies to nomena nuda. I've considered 
referring to them as "rejected" but that sounds like I mean a nomen 
rejectum. Is there an actual term that I can use for non-accepted genera 
and species?

A good question indeed, since the same terminology is often used to 
designate the status of both taxa and nomina. We should first 
distinguish "invalid nomina" and "invalid taxa". The status of a nomen 
involves the International Code of Zoological Nomenclature (for an 
animal): "invalid" refers here to the nomenclatural status of the nomen 
and is objective. The status of a taxon, however, is independent from 
that of the nomen. Its status is given by taxonomists who judge if this 
taxon (i.e. the holotype/type species/type genus and hypodigm) is 
diagnosable.

In short:

Nomen: object => Nomenclatural status (objective).
Taxon: concept => Taxonomic status (subjective).

Therefore:

Synonymy => Taxonomy - except in the case of objective synonymy (same 
holotype/type species/type genus) where it involves nomenclature.
Nomina dubia => Taxonomy.
Nomina nuda => Nomenclature.
Lapsus calami => Nomenclature.
Homonymy => Nomenclature.

In most papers, however, scientists say "taxon" when they mean 
"nomen"... The difference is significant, though: an invalid taxon MAY 
have a valid nomen, but a valid taxon MUST have a valid nomen. Also, 
taxa invalidated by taxonomists should be distinguished from those 
bearing an invalid name. Practically, we could call these cases: 
nomenclatural/taxonomic validity, or subjective/objective validity.

A nomenclaturally invalid taxon would thus bear a nomen nudum, but a 
taxonomically invalid taxon could bear a nomen nudum or a nomen dubium, 
or any nomen following the rules of the ICZN.

Let's take for example:

> The Spanish sauropod taxon Galveosaurus:

Its holotype was described independently by Sánchez-Hernández and Barco 
et al. in 2005, as respectively Galveosaurus herreroi and Galvesaurus 
herreroi. Both nomina follow the rules of the ICZN, and are thus 
nomenclaturally valid. As they are based on the same holotype, they are 
objective synonyms and only the senior synonym, Galveosaurus, is valid 
regarding the ICZN.

> The English sauropod Cetiosaurus:

The holotype of its type species, Cetiosaurus brevis, is undiagnostic 
according to Upchurch and Martin (2003). Although Cetiosaurus and 
Cetiosaurus brevis are valid regarding nomenclature, they are invalid 
regarding taxonomy (nomina dubia). Cetiosaurus includes also C. 
oxoniensis, which is based on diagnosable material. If the ICZN accepts 
to suppress C. brevis as proposed by Upchurch et al. and chooses instead 
C. oxoniensis as type specie, then Cetiosaurus would be valid 
nomenclaturally AND taxonomically.

> The Nigerien iguanodont Gravisaurus tenerensis:

This nomen was erected in the PhD dissertation of Chabli in 1988, but it 
is not published sensu the ICZN. Even if the specimen described 
represent indeed a new taxon according to taxonomists, this taxon was 
invalid taxonomically until it was given a proper name - Lurdusaurus 
tenerensis - in 1999 by Taquet and Russell.

Cheers,
Jocelyn Falconnet


PS: I just had an idea; what do you think of: "approved"/"reprouved" for 
taxonomy and "valid"/"invalid" for nomenclature ?