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RE: Nomina Dubia Part II: Rapator

Michael Mortimer <mickey_mortimer111@msn.com> wrote:

> No one ever suggested naming new taxa based on fragmentary
> remains is a good rule to follow, we're talking about how to
> deal with them once they've already been named. 

But isn't it the same thing?  Only the tense has changed.  Either way, the 
remains are fragmentary and probably do not justify a name.

> You're
> being pragmatic and following the status quo in treating
> fragmentary specimens as nomina dubia once they've been
> called such by an authority because that's easier than doing
> the detailed comparative work and making the tough
> synonymization decisions.

I wouldn't have quite put it in those words... but in essence you're not far 
off what I'm driving at.  Especially since the detailed comparative work is 
probably going to be inconclusive anyway, because the specimens in question are 
so fragmentary (e.g., _Rapator_, _Ceratops_).

The only reason these particular specimens are getting attention at all is that 
they were named (i.e., made the type of a genus or species).  I don't think 
it's worth tying ourselves into knots in an attempt to salvage these names.  
Yes, it would be nice if _Ceratops_ was a valid genus.  Maybe one day it will 
be, if the original site is re-discovered and material is recovered that 
matches the _Ceratops_ type (opening the way for a neotype).  But that hasn't 
happened... yet.

> Again, my issue with your methodology is its
> subjectivity.  What's "compelling"?  What
> autapomorphies are "striking"?  Does Struthiomimus have
> any striking autapomorphies?  Are you compelled by the
> manus being slightly longer compared to the humerus than
> other ornithomimosaurs?  Would you name Struthiomimus
> today based on those characters I listed?  If not it
> seems like a problem since it's a universally recognized
> valid taxon, if so it seems you're being inconsistant since
> you reject those kinds of characters for poorly known taxa
> like Rapator.  Things are only going to get more subtle
> in the future as we find m

> the gap between what seem like distinctive characters now,
> and more specimens of taxa that will show characters that
> seem valid today are due to individual or ontogenetic
> variation.

I admit the system is subjective.  This is a gray area: nomina dubia are in the 
eye of the beholder.  But I think this is OK.  On that point, David M. made 
this statement:

      As soon as you can't answer the question "if I were wrong, how 
      would I know?" any longer, you're not doing science. 

I think this is too harsh when applied to paleontology and biology, because 
frequently we deal in probabilities, rather than absolute certainties.  That's 
why statistics are so important.  For example, one phylogeny does not 
*disprove* another phylogeny; one phylogeny is only deemed more probable based 
on a set of pre-determined assumptions (such as parsimony).  Similarly, if we 
carried out an exhaustive morphometric analysis of ceratopsian horn cores which 
incorporated every known specimen, it may indicate whether the traits of the 
_Ceratops_ horn cores are likely to be the result of intraspecific variation or 
not.  But all that effort... for what?  Although we are testing a hypothesis, 
nothing can be refuted.  We would still not know if we were "wrong".

When it comes to nomina dubia, there is no universal metric.  I'm only focusing 
on those names that pose taxonomic and nomenclatural problems, like _Ceratops_, 
the name-giving genus of one of the most best-known dinosaur families, the 
Ceratopsidae.  I don't think it's worth propping up the name _Ceratops_ purely 
for bookkeeping reasons.  Nor do I think we need an exhaustive comparative 
analysis in order to dismiss _Ceratops_ as a nomen dubium.  Ditto for _Rapator_.