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RE: Troodon and other problems (was Andrew McDonald response re: European iguanodonts)



To Tim, who wrote:

<I don't believe this is at all correct.  While it is true that the type 
material for _T. indicus_ comes from Bara Simla Hill of Jabalpur, the holotype 
of _T. colberti_ (now the type species for _Isisaurus_) hails from Dongargaon.  
Although both specimens were recovered from the Lameta Formation, the sites 
themselves aren't even in the same state of India.  Moreover, the type 
mid-caudal vertebrae of _T. indicus_ are very different in morphology to those 
of _I. colberti_, so it's highly unlikely that _T. indicus_ and _I. colberti_ 
could represent the same species.
 
The type material of _T. indicus_ was found at the same site as the holotype of 
_Antarctosaurus septentrionalis_ (now the type species for _Jainosaurus_).  
When you say _Isisaurus_, do you perhaps mean _Jainosaurus_?>

I probably did mean Antarctosaurus, but the mistake has been made.

To Greg Paul, who wrote:

<One good rule would be to no longer accept dinosaur teeth as holotypes,>

  I thought this was my schtick? No, seriously, for the longest time I though 
the first paper I would ever write would be to stop telling people to use teeth 
as holotypes. It won't, but I have since mellowed this stance for a variety of 
reasons:

   1. Teeth, even in series, are useful body fossils and used for taxonomic 
practices (such as extending ranges) that have deliberate taxonomic utility: 
they may be referred to broader taxonomy than the species, but this still 
validates their use in taxonomy. But the argument is about holotypes, so...

  2. Like any other body fossil, a single tooth may be just as likely as any 
other (maxilla, frontal, laterosphenoid, cuneiform, caudla vertebra) to 
bear autapomorphies, even completely exclusive autapomorphies. This 
seems to be more true for teeth in mammals than in reptiles, or was 
until the "notosuchians" and their wonderful dentitions came to light.

  3. If teeth (or dental series) are not likely to bear autapomorphies, then 
and only then do they become less useful.

  Greg, you're advocating low level of material in general, and conflating 
teeth into that, allowing you to dismiss *Ornithomimus velox*. I do not think 
that unless you can positively show it lacks any potential autapomorphy or 
autapomorphic suite, such an action is useful. This unfortunately coincides 
with the illusion of only complete specimens are useful for taxonomy, as this 
is certainly not the case (even 10% complete alvarezsaurs are popping up with 
distinctive and sometimes autapomoprhic features of the forelimbs, hindlimbs, 
or vertebrae, and of course Hone et al. have a paper in press on a new 
tyrannosaurid based on a maxilla and partial (nearly complete) dentary and 
little other material). How complete is "complete enough?" and how do you 
qualify that?

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





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> Date: Sun, 3 Apr 2011 22:32:52 -0400
> From: GSP1954@aol.com
> To: dinosaur@usc.edu
> Subject: Troodon and other problems (was Andrew McDonald response re: 
> European iguanodonts
>
> One of the things I was trying to do in the field guide was raise some of
> these taxanomic issues by not going along with the standard designations. To
> be frank I was shocked to see how bad the situation is with so many run of
> the mill taxa we use all the time with little thought.
>
> One good rule would be to no longer accept dinosaur teeth as holotypes,
> which does in Troodon. This would leave Stenonychosaurus inequalis as the best
> skeletal based species, not that the holotype of that is much to right home
> about either. The only skeletal remains that should be placed in the same
> species should be those that are from the same horizon, the rest should be S.
> sp. unless it becomes possible to either unite or distinguish them.
>
> It is not just a tooth problem. The holotype of Ornithomimus is extremely
> dubious at best. That of Struthiomimus is not great shakes either. All those
> taxa are sort of floating. There are the Mamenchisaurus and Omeisaurus
> messes. Diplodocus is a ticking time bomb. Don't get me started on some of the
> late Cret N Amer ankylosaurs. It's one thing after another.
>
> GSPaul