[Taxacom] Descriptive suprafamilial names of plants

[Paul van Rijckevorsel]

Hmm, some points:

* The "Magnoliophyta is an automatically typified name,
    being based on the genus Magnolia which, in turn,
    is typified on a single species (M. virginiana). "
is not accurate. Magnoliophyta is typified by the same specimen
as is M. virginiana (Art. 10.7, 10.1).

* It is quite true that the question of what belongs to
Magnoliophyta beyond that specimen is a entirely a taxonomic
question.

* A descriptive name may be used unchanged at different ranks,
and, just as names like Magnoliophyta, may be applied to
a taxon that is defined however one may wish; no difference here.

* Principle IV of the ICNafp is limited by "except in specified cases",
and names above the rank of family are all excepted (Art. 11.10),
so no difference there. In a fairly well-known paper by Chase & Reveal
(2009), a choice was made to adopt Equisetopsida for the embryophytes,
and many people have expresses their unhappyness about this choice
(having a preference for, say, Magnoliopsida, which would have been
equally correct, but more pleasing). Some even went so far as to publish
Embryopsida as a 'better' name.

* It is not true that
    "the second author who proposes Angiospermae with a different
     circumscription creates a later homonym ..."
A name published as consisting of A + B + C + D is not validly
published (Art. 36.1(d)); a "description or diagnosis" is required.
Also, an emended description or diagnosis is certainly quite common
for typified names. For a descriptive name to be a homonym it would
need to apply to a quite different group (Centrospermae for a group
of algae as opposed to a group of plants). However, there are no
restrictions on the use of homonyms for names above the rank of genus
(families excepted). (And, yes, I am on the record as being unhappy
with this.) As Art. 53 Ex. 5 (included on a proposal by Reveal &
Ghandi) points out, the names Moreae (based on Mora) and Moreae
(based on Morus) both are legitimate and may be used (if appropriate).
Under the rules, there is nothing to prevent anybody from
constructing a system of classification that uses both Moropsida
(based on Mora) and Moropsida (based on Morus) for two
different groups, so, again, there is no difference here. Anybody
sane would choose the names he adopts carefully, but abuse is
possible for both categories of names.

* So, the choice to use an automatically typified name or a
descriptive name is a free one, with little or no difference
under the rules. To me, the most important factor is that
a name like Magnoliopsida has been so overused that it
is becoming meaningless. It is a fairly safe bet that it is most
commonly used in the sense of Cronquist, but as the system
by Cronquist loses following, the reader increasingly is left
in doubt as to what such a name may refer to. With a name
like Angiospermae I am in no doubt what group is meant,
and this to me is highly valuable.

Paul

----- Original Message ----- 
From: "Jim L. Reveal" <jlr326 at cornell.edu>
To: <taxacom at mailman.nhm.ku.edu>
Sent: Sunday, November 24, 2013 4:53 PM
Subject: [Taxacom] Descriptive suprafamilial names of plants


> According to Art. 16 of International Code of Nomenclature for algae,
> fungi, and plants (ICN), names above the rank of family may be (a)
> automatically typified or (b) descriptive. Magnoliophyta is an
> automatically typified name, being based on the genus Magnolia which, in
> turn, is typified on a single species (M. virginiana). That epithet is
> typified on a single specimen and this is the only element that must be
> termed M. virginiana, Magnolia, Magnoliaceae, Magnoliales, Magnoliophyta,
> or any other suprageneric name based on the genus Magnolia.
>
> All other element associated with Magnolia virginiana, or any other taxon
> above that rank, including any other specimens, is strictly a taxonomic
> decision.
>
> A descriptive name is not based on a generic name, may be used unchanged
> at different ranks, and may be defined however one may wish. Descriptive
> terms like Angiospermae, Gymnospermae, Coniferae, Centrospermae are
> circumscribe however one may wish and, in fact, have been. Some author
> define Coniferae to include all gymnosperms, but other restrict their
> concept to just the conifers. Centrospermae has been used for groups of
> algae as well as plants. Authorships are impossible to define as the
> addition or subtraction of any taxon alters the circumscription. Thus,
> such names violate Principle IV of ICN, at least in principle, that a
> taxon have "a particular circumscription, position, and rank" and "can
> bear only one correct name."
>
> Arguably, therefore, for a descriptive name to be used as proposed by the
> original author of the name, say Angiospermae, that author must have
> included in that group all possible taxa and no newly discovered entity
> can be added because to do so this would alter the original
> circumscription. Thus, the second author who proposes Angiospermae with a
> different circumscription creates a later homonym because, as required in
> Principle IV, the earliest name must be used.
>
> Now, this is silly, of course, and today one actually applies the rules of
> nomenclature to descriptive names in the most general and purposefully
> vague ways as possible. Fortunately, no one questions any action and we
> all pretend that use of a specific descriptive name has been followed "in
> accordance with the rules."
>
> Given the problems with descriptive name, I strongly urge that one use
> names that can be typified and that descriptive names should be used only
> as informal terms. Thus, Magnoliophyta or angiosperms; Pinophyta or
> gymnosperms. As Principle II states: "The application of names of
> taxonomic groups is determined by means of nomenclatural types."
>
> Jim Reveal
>
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