RE: Alamosaurus as biggest North American sauropod

[Mickey Mortimer <mickey_mortimer111@msn.com>]

Since my name was invoked as an acronym, I'll argue for the philosophy (not 
that it's uniquely mine).  First I'll specify that a specimen must not differ 
from at least two other taxa in anatomical details which are taxonomically 
significant for it to be a nomen dubium.  Note that the "taxonomically 
significant" clause leaves lots of room for subjectivity when it comes to 
Mesozoic dinosaurs.  For example, the London and Munich Archaeopteryx specimens 
DO differ from each other, but I don't feel the differences indicate multiple 
taxa.  If someone argues differently, I can point to examples of variation in 
other species (e.g. living ones, ones preserved in mass bonebeds), but 
ultimately it's a probability argument.  Also note that stratigraphy, 
geography, ontogeny and sexual dimorphism can and should inform taxonomic 
evaluations, though I don't think differences in these areas should count as 
taxonomically significant (indeed the latter two are by definition NOT 
taxonomically significant).

Given those caveats, I agree the philosophy isn't necessarily stable and will 
require revisions as more material is found.  Maybe two or more taxa are hiding 
in what we now call Tyrannosaurus rex, and in that case if the holotype cannot 
be assigned to either species, it should indeed be declared a nomen dubium OR a 
neotype should be chosen among more diagnostic specimens.  This is simply the 
price of science never presenting us complete knowledge.  I'd like to know what 
your alternative philosophy is.  Keep what are apparently two species 
synonymous, and thus not represent phylogeny with taxonomy?  Pretend that the 
T. rex holotype can be referred to one of the species, and thus lie for the 
sake of stability?

Mickey Mortimer

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> Date: Fri, 9 Dec 2011 08:10:27 -0500
> From: martyniuk@gmail.com
> To: qi_leong@hotmail.com
> CC: tijawi@gmail.com; dinosaur@usc.edu
> Subject: Re: Alamosaurus as biggest North American sauropod
>
> On Thu, Dec 8, 2011 at 7:58 PM, Jaime Headden <qi_leong@hotmail.com> wrote:
> >
> >   The best strategy, in my opinion, is to simply do away with crap taxa. If 
> > you base your nomen on crap, and you can't distinguish it from two or more 
> > taxa (MMM = Mickey Mortimer's metric), regardless of its provenance, 
> > horizon, or the authors' preclusions about its ontogeny or gender, then 
> > that nomen deserves to be relegated to the annals of me laughing at you 
> > (the nomen, not the descriptors).
>
> This is completely unsustainable and revisionist. _Titanosaurus
> indicus_ was not a "crap taxon" when it was described. It was
> perfectly diagnosable relative to knowledge of sauropods *at that
> time*. A century of further discoveries rendered it "crap" *in
> comparison to* more and better finds.
>
> By this philosophy, we should never name any fossil taxa (or many
> modern taxa for that matter) for fear that further research may render
> previously diagnostic characters uninformative. Think the holotype of
> _Tyrannosaurus_ is diagnostic? What if in ten years we find that, say,
> the number of metacarpals varies between species of tyrannosaurines?
> Or we find mummified specimens showing that some had different
> patterns of squamation that could not be predicted by osteology? Even
> if none of those specimens and no variation can be found within the
> same geographic or stratigraphic level as the holotype, is the
> _Tyrannosaurus_ then a declared a "crap taxon"?
>
> Matt