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Re: Horner's Pachy Lumpin' - Your Thoughts?



Another picture of the Triebold specimen (also might be of interest since it 
apparently represents a 45% complete skeleton):

http://www.rmdrc.com/images/exhibit_pachy.jpg

--- On Fri, 1/8/10, Zach Armstrong <zach.armstrong64@yahoo.com> wrote:

> From: Zach Armstrong <zach.armstrong64@yahoo.com>
> Subject: Re: Horner's Pachy Lumpin' - Your Thoughts?
> To: dinosaur@usc.edu
> Date: Friday, January 8, 2010, 11:24 AM
> Tracy Ford, in Prehistoric Times
> issue #73 "How to Draw Dinosaurs-Spiky Pachycephalosaurs?"
> commented that there are known Pachycephalosaurus skulls
> with spikes, not nobs, which means no loss of horns nor
> "absorbtion" of horns is needed. One of the skulls was
> reported to have been found by Mike Triebold. Ford reports
> that the Black Hills Institute has a spiked
> Pachycephalosaurus skull. I am not sure if this is the same
> as Ford's drawing of the "Sandy Site" Pachycephalosaurus of
> that same issue, but a photo of the Sandy Site skull in all
> its spiky glory can be found here: http://www.wmnh.com/wmtr0000.htm
> 
> I should also point out that in PT #75, there is a
> Pachycephalosaurus skeletal done by Greg Paul that has long
> spikes, too. I am not sure of his reasoning on this, but I'm
> sure he has a good one :)
> 
> If these skulls indeed are referable to Pachycephalosaurus,
> that means the "Dracorex" juvenile would not have needed to
> lose any horns or re-absorb them at all. Also, as far as I
> know, Stygimoloch is only known from a fragmentary skull
> which could explain the differing spike counts.
> 
> Best regards,
> 
> Zach
> 
> 
> 
> ----- Original Message ----
> From: Tor Bertin <nightimeshadow@yahoo.com>
> To: dinosaur@usc.edu
> Sent: Thu, January 7, 2010 9:38:50 PM
> Subject: RE: Horner's Pachy Lumpin' - Your Thoughts?
> 
> > Horner likewise did not attempt to explain this, from
> the
> > Bakker et al. description of _Dracorex_:
> "_Stygimoloch
> > spinifer_ is characterized by a huge spike cluster,
> > consisting of 3 enlarged (hypertrophied) spikes. This
> > differs from t
rangement in
> _Dracorex
> > hogwartsia_" (Bakker et al. 2006, page 11). If 'Draco'
> has
> > four horns, and 'Stygi' has three, then we've lost a
> horn
> > during ontogeny. This interesting quirk is not touched
> upon,
> > nowhere in Horner and Goodwin (2009) is the
> ontogenetic loss
> > of a horn mentioned.
> 
> It's possible that it's a population difference. I'm not
> sure what kind of sample size there is (is there more than
> one skull known for _Dracorex_ and _Stygimoloch_?), but if
> the number of spikes varied on a creature to creature basis,
> it wouldn't be quite so unusual.
> 
> 
>       
>