Re: tiny-armed theropods

[Tim Williams <tijawi@gmail.com>]

Mickey Mortimer <mickey_mortimer111@msn.com> wrote:


> I don't know where you got the idea that nomina dubia aren't taxa or 
> organisms.  Troodon formosus is a real animal, diagnostic
> holotype or not.  There was a living organism which the type tooth of Troodon 
> belonged to, and this individual can be included in a
> phlogenetic analysis, regardless of whether additional individuals could be 
> assigned to its species.


Of course the tooth of _Troodon formosus_ came from a real animal.
I'm not suggesting it was carved out of stone by Cretaceous trolls.


But if a genus is declared a nomen dubium, then it no longer denotes a
real taxon.  For example, the teeth named _Deinodon horridus_ (a nomen
dubium) could belong to any number of tyrannosaurid species.  So
although the teeth came from a real individual, that individual does
not represent a distinct taxon.  Thus, it would serve no purpose to
code the teeth and put them into a phylogenetic analysis.  Yes, you
*could* put _Deinodon_ into a phylogenetic analysis.  But it's like a
dog chasing a car: it can be done - but what's  the point?


> There's no rule that says only taxa or only valid taxa can be included in 
> such analyses.


Yes, I know.  But since a nomen dubium no longer represents a real or
distinct taxon, it's removed from taxonomic consideration.  Sticking a
nomen dubium into an analysis is just going through the motions.  It's
not advancing the scientific process in any way.  The only reason you
would include a nomen dubium in an analysis is if it happens to be a
name-nearing taxon of a clade, which strikes me as circular reasoning.
 I'd prefer that nomina dubia be excluded from clade definitions.


> The microraptorian NGMC 91 is included by Senter (2007) for instance, despite 
> being only a single individual that has not been
> conclusively differentiated from Sinornithosaurus.  Indeed, it has only been 
> described as Dromaeosauridae gen. et sp. indet. and
> Sinornithosaurus sp. indet..


IMHO this is irrelevant.  If NGMC 91 is recovered as a distinct taxon
in the analysis, then it is no longer indeterminate.  On the other
hand, if it cannot be conclusively differentiated from
_Sinornithosaurus_, and can be conclusively differentiated from other
dromaeosaurids - then NGMC 91 belongs in _Sinornithosaurus_.



> What's the point of having a rulebook for a community if they only follow the 
> rules they want to anyway?  It's like enforcing laws only
> when they don't inconvenience you.  We might as well just get rid of the ICZN 
> if we're going to call it wrong when we don't like what it
> says.


Well, now that you mention it...  :-)  I have repeatedly opined that
the ICZN Code should *not* apply to family-level taxa (family,
subfamily, tribe, superfamily), only to genera and species.  So while
I don't advocate completely getting rid of the ICZN, it's focus should
be removed from family-level taxa.  It just causes too many problems
when phrasing sensible phylogenetic definitions.






Cheers

Tim