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RE: Platecarpus tympaniticus - how to analyze a nomen dubium





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> Date: Tue, 21 Sep 2010 11:34:05 +0200
> From: david.marjanovic@gmx.at
> To: dinosaur@usc.edu
> Subject: Re: Platecarpus tympaniticus - how to analyze a nomen dubium

> *Ceratops*: has anyone even looked at the material in the last couple of
> decades?
 
Wait....if nobody's looked at the material, what has this discussion been 
running on?  (theory and ideals?)
 
 
 
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> Date: Tue, 21 Sep 2010 00:39:51 -0700
> From: tijawi@yahoo.com
> To: dinosaur@usc.edu
> CC: tijawi@yahoo.com
> Subject: Re: Platecarpus tympaniticus - how to analyze a nomen dubium
>
>
> On Mon, 20/9/10, Michael Mortimer wrote:
>
>
> > Tim Williams and I have been having quite a discussion on
> > the DML this year about nomina dubia and how they should be
> > treated. In the most recent JVP, Konishi et al. (2010)
> > present an excellent example of my philosophy in this
> > matter. Platecarpus tympaniticus is the type species of
> > this well known genus of mosasaurs. It's based on
> > fragments described by Leidy back in 1865 and ignored
> > (Williston, 1898) or declared a nomen dubium (Russell, 1967)
> > since.


> But I think I know where you're headed here. I'm willing to give taxa based 
> on fragmentary material a fair go. But... IMHO for the sake of taxonomic 
> stability, such taxa should not give their names to higher-level taxonomy. 
> This is because phylogenetic definitions of family-level clades include the 
> name-giving taxon as a specifier (which makes sense), so we should choose 
> name-giving taxa with care.
 
 Except none of us are precognitive -  we don't know that better species will 
be found.  (we hope they will, but its not a guarantee)
 
 
okay, let's say that, twenty years from now, I discover a dinosaur that is as 
related to other Archosaurs as the Pangolins are to other Mammalia.
 
When I and my co-describers name it, are we supposed to leave its 
classificiation blank?:
Kingdom: Animalia
 Phylum: Chordata
 Class: Reptilia 
Superorder: Dinosauria
 Order: Saurischia
Suborder:  ??
Family:  No clue
Subfamily:  did you not read the above?
Genus:  Allonovadontatherus
Species:  redcliff
 
or should I fill in the blanks myself?
 
(after all, neither I nor my co-describers know that, thirty years after our 
publication, other Allonoadontatherids would be discovered, ones who better 
show the relationship between their genus and other Dinosauria, and are get 
names that sound better at the Family level)
 
 
> > Incidentally, note that despite the fact Russell
> > thought it was indeterminate within the genus Platecarpus,
> > he retained it as the type species and kept other diagnostic
> > species in the genus (like I'm recommending for
> > Stegosaurus).
>
> This sounds like a very bad idea. Note that a fossil species is supposed to 
> represent a distinct biological entity: a species. Maintaining a 
> non-diagnostic type species solely for bookkeeping reasons strikes me as 
> going against the entire purpose of biological taxonomy.
 
 as long as _Deinodon_ isn't discovered to be a crocodile, why does it matter 
whether its or T.rex's name is on the Superfamily?
 
(and don't say "because I'm more familiar with it"...because if that's the 
answer, then how is paleontology supposed to survive your (far away) death?)
 
 
> Taxonomy is not just about compiling lists. It's a way of classifying real 
> species. If we cannot demonstrate that _S. armatus_ was a separate species 
> (because the type material cannot be distinguished from diagnostic 
> _Stegosaurus_ species) then the taxon is toast. P
> here's no good evidence that this ever represented a real species, then let 
> it go. There's no point converting it into an OTU, and running a phylogenetic 
> analysis with it - all for the sake of keeping Ceratopsidae afloat. Sure, 
> _Ceratops montanus_ might be a real taxon; but we're probably going to need 
> more material to confirm this. Until this day comes (and it may never come), 
> then let's stop playing silly-buggers and pretending that it's fine to have 
> _Ceratops_ as an appropriate name-giving genus for an important family of 
> dinosaurs.
 
  shouldn't the burden of proof lie on proving that _Ceratops_ *is not* a good 
genus, rather than say "we should kill it because we're not sure" ?
 
 though, if it helps any, you can rename _Ceratopsidae_ the _Docimoidae_ so 
that there's no ugly politics or bitter arguments over what to rename the clade 
before conclusive proof one way or another arrives.