Re: tiny-armed theropods

[Tim Williams <tijawi@gmail.com>]

Mickey Mortimer <mickey_mortimer111@msn.com> wrote:

> Tim and I have had this battle enough times that we're familiar with each 
> others' opinions and
> talking points, but I couldn't pass this up...


And I can't pass up responding.  :-)


> By that reasoning, we'd have to include Passer in the analysis too, which I 
> don't think you'd agree
> with.  Just as we can use our extra-analysis knowledge to be fairly certain 
> Passer is closer to
> e.g. Anser, Yanornis, Confuciusornis etc. than to dromaeosaurids, 
> troodontids, oviraptorosaurs,
> etc., we can use it to be fairly certain Troodon is closest to Zanabazar, 
> Talos, Saurornithoides
> and such.  There's no need to include every definition-related taxon in an 
> analysis.


This is a non sequitur.  _Passer_ exists.  It's a real animal - and a
real taxon.  However, if _Troodon_ becomes a nomen dubium, it is no
longer a valid taxon.  It therefore no longer represents a once
living, breathing animal.  It is *just* a name.  As a nomen dubium we
are precluded from referring any more material to it.  If _Troodon_ is
a nomen dubium then, no, I can't be certain that _Troodon_ is closest
to _Zanabazar_, _Talos_, and _Saurornithoides_ because there is no
such thing as _Troodon_!


This separates a nomen dubium from other taxa based on poor material
that is nevertheless diagnostic.  For example, nomina dubia such as
_Deinodon_ and _Trachodon_ are no longer relevant to discussions on
tyrannosaur or hadrosaur phylogeny.  So it's ridiculous to include
them in a phylogenetic analysis, or (and this directly addresses your
point) even treat them as taxa.  No one talks about _Deinodon_ and
_Trachodon_ as if they were real, distinct animals.  As nomina dubia,
they are merely names.


> Just think of how few analyses include Enantiornis, Therizinosaurus, 
> Megalosaurus, Spinosaurus,
> etc..


Yes, but you *could* include these taxa in an analysis, and it would
be a productive exercise to do so.  At this stage, all are considered
valid OTUs.  By contrast, when nomina dubia are put into a
phylogenetic analysis, it would solely be for bookkeeping reasons.


> As I've said before on the DML, people just cherry pick from the ICZN and 
> make up their own
> rules, such as those involving nomina dubia.  They see their own subjective 
> ideas of stability as
> overruling the ICZN, and if the majority follows them, what can we do but go 
> along with the
> arbitrary flow?


And more power to them.  The ICZN should serve the community, not the
other way round.  If the ICZN rules say Deinodontidae should be used
instead of Tyrannosauridae, I say it's the ICZN rules that are wrong.





Cheers

Tim