[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: New papers in Geobios (and nomenclatoral gripe)
Christopher Taylor wrote:
And that's my argument, really - Sachs and Hornung have recognised a
genus that includes the type specimens of _Mochlodon_ and _Zalmoxes_, and
as the former is the older name, priority
requires that it be the name of the genus.
The ICZN stipulates that a type specimen cannot be used to typify a genus
without reference to the type species (61.1.2.). A genus is defined
objectively by its type species, and a type species is defined objectively
by its type specimen(s). But a genus cannot be objectively defined by the
type specimen(s) of its type species. This distinction may appear subtle
and esoteric, but it has the effect of rendering taxonomically invalid any
species for which the type specimen(s) cannot be identified to the level of
How does this relate to the case of _Mochlodon_ v _Zalmoxes_? Although the
type specimen for _M. suessi_ can be identified to the level of genus, the
fact that it cannot be identified to the level of species (i.e., it is a
nomen dubium) also makes _Mochlodon_ taxonomically invalid. For the
purposes of nomenclature, we can't have _Mochlodon_ without first
demonstrating that its type species (_M. suessi_) is taxonomically valid.
Simply demonstrating that the type material for _M. suessi_ is diagnostic at
the genus level is insufficient.
In other words, although there is no ICZN rule which explicitly states that
a genus is taxomically invalid if its type species is a nomen dubium, the
rules are crafted in such a way that this is what happens anyway.
I think I get what you're arguing, Tim (emphasis on _think_ - my
sincere apologies if I've misunderstood you).
No, you've understood me loud and clear. That's probably more a credit to
you than to me. :-)
However, I don't think I'd agree with you. I've always understood this to
mean that 'genus A
is the genus that it's type species belongs to', etc. Every specimen must
have fallen into one species or another, even if we can't identify which
species it was for the material we have available.
There lies the rub. Taxonomy is about identification, and named species
that cannot be identified to the level of species are nomina dubia.
Therefore, the fact that we can't identify the species characteristics of
_Mochlodon suessi_ is irrelevant to the question of what genus it belongs
to - _if_ we can demonstrate that 'whatever
species this was, it fell within this genus'.
If I understand 61.1.2. correctly, the ICZN sets the bar a little higher
than that. The fact that we can't identify the species characteristics of
_Mochlodon suessi_ is very much relevant to the question of what genus it
belongs to. In this case, anyway. If _Zalmoxes_ was monotypic (i.e.,
_shqiperorum_=_robustus_), then the genus-level and species-level characters
would be the same, and _Mochlodon suessi_ would be valid at the
species-level, and so _Mochlodon_ have priority over _Zalmoxes_.
Again, I wouldn't have such a narrow view of the ICZN as you. The type
specimen must by definition belong to the species it typifies, and every
specimen must have belonged to one species or another.
In the 'real world', yes. We know that _Antrodemus valens_ didn't stalk the
Jurassic terrain as a disembodied tailbone, for example. But taxonomy
places a lot of stock in what a specimen can be *demonstrated* to belong to.
While the current specimen of _Antrodemus valens_ does not possess the
characters necessary to reliably identify it, the individual it came from
would have probably done so while alive. And yes,
_Antrodemus_ would take priority over _Allosaurus_ - _if_ we could
demonstrate the two to be congeneric.
This would be problematic in terms of taxonomy. In order for _Antrodemus_
to be valid, _A. valens_ (the type species) would have to be valid. This is
analogous to _Mochlodon_: in order for _Mochlodon_ to be valid, _M. suessi_
(the type species) would have to be valid.