RE: Andrew McDonald response re: European iguanodonts

[Jaime Headden <qi_leong@hotmail.com>]

  1. *Pectinodon bakkeri* is named for a crown with mesial denticulation. It is 
from the Maastrichtian Lance Formation, and is thus almost 10ma younger than 
*Troodon formosus* (75mya). Prove to me it is the same taxon as *Troodon 
formosus.*

  2. The position in the dental series of ANSP 9259 has been speculation, most 
recently and following that of Currie (1987) as a premaxillary crown, but this 
is not based on any material association with a jaw bone and _in situ_ crowns: 
Currie (1987) merely argues (pp.76-77) that "The type specimen of *Troodon 
formosus* [...] is a premaxillary tooth, or possibly an anterior maxillary." He 
then goes on to describes samples of teeth, all essentially shed or broken and 
not _in situ_, to bolster the claim that the type tooth does not conform to 
known dentary or inferred maxillary crowns; this is done by inferring the 
position of premaxillary crowns from the sample and distinguishing them from 
other series. It is made problematic that the only bones so far reported with 
_in situ_ dentition are mandibular, and that these teeth vary in their relative 
denticulation (Currie, 1987). They are also from varying formations, and given 
taxic variation within the Dinosaur Park Formation itself, both theropod and 
ornithischian, I find it problematic to associate even one iota of this 
material to *Troodon formosus* solely because one tooth possesses denticulation 
on the mesial carina.

  Now, don't get me wrong: I am amazed and fascinated by Currie, both as a 
scientist and as a writer. He's my paleo-hero, above all others. But I think 
he's fundamentally wrong here, as are so many others who have had to sort 
through theropod dentition samples, by assuming the quality and position of odd 
teeth. Currie (1987) writes (pg.76): "*Troodon* teeth vary in relation to their 
position in the jaw, and this has been the major reason that the taxonomic 
status of this animal has been so uncertain." Yet despite this, while some 
certainty exists, marked divergence of ANSP 9259 from every single _in situ_ 
troodontid crown has made associating nomenclature problematic. Yet still, 
thousands of teeth from the Campanian and Maastrichtian of North America are 
referred _solely_ to *Troodon formosus.* 

  3. Absence of mesial denticulation in premaxillary crowns of virtually all 
other troodontids named to date (Norell et al. 2009 confirming Mickey's 
assertion "Not Saurornithoides, Zanabazar (contra Barsbold, 1974)" and its 
likely but uncited source) does not mean only one taxon with mesial 
denticulation exists. This is compounded by the broad stratigraphic and 
geographic distance of occurence of such teeth in North America.

  4. If I were to assume that *Pectinodon bakkeri* has as much "right" to exist 
alongside *Troodon formosus* as *Zanabazar junior* does to *Saurornithoides 
mongoliensis*, then it matters strongly how many species might exist and by 
what "level" of nomenclature we recognize their taxonomy. I do not think you 
can argue correctly that *Troodon* should be the appropriate container, because 
there is no means of distinguishing this result from one placing all species 
into their own equivalent containers (thereby permitting *Pectinodon* alongside 
*Troodon*). I would then reject the notion that *Troodon* would be a useful 
container at all for any quanta of material broader than a morphology precisely 
identical to the holotype specimen, and almost certainly from only the Judith 
River Formation of Montana (that is, also not from the Two Medicine, Dinosaur 
Park, etc.). Is this a ludicrous and over-conservative opinion? You betcha. But 
these are _shed and broken teeth_, and using them to validate variation of an 
unknown quality (especially given their uniqueness) is itself ludicrous.

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: Mon, 4 Apr 2011 05:46:18 -0700
> From: mickey_mortimer111@msn.com
> To: dinosaur@usc.edu
> Subject: RE: Andrew McDonald response re: European iguanodonts
>
>
> Good call.  As for Troodon, I'd like to know what other troodontids have 
> mesial serrations, or serrated premaxillary teeth for that matter.  Not 
> Saurornithoides, Zanabazar (contra Barsbold, 1974), Byronosaurus, 
> Sinornithoides, Sinusonasus, etc..  Troodon looks valid to me, regardless of 
> how many species are encompassed by what we call Troodon formosus.
>
> Mickey Mortimer
>
> ----------------------------------------
> > Date: Mon, 4 Apr 2011 12:17:38 +0200
> > From: david.marjanovic@gmx.at
> > To: dinosaur@usc.edu
> > Subject: Re: Andrew McDonald response re: European iguanodonts
> >
> > Before Mickey Mortimer wakes up...
> >
> > > Under these circumstances, either _T. formosus_ is a nomen dubium, or
> > > a new holotype (neotype) would be designated in order to keep the
> > > genus _Troodon_ as a valid taxon (as was done with _Iguanodon_). If
> > > the former, we would go back to calling the family
> > > Saurornithoididae.
> >
> > No, why?
> >
> > There's no reason to dump Ceratopsidae or Titanosauridae either.
>