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




M. Erickson said:

>[some editing] ... the burden of proof still lies with Horner - because well, 
>let's face it, his hypothesis is extremely bizarre and counter-intuitive

I don't see why the hypothesis is extremely bizarre, nor counter-intuitive. 
Besides, these are not scientific terms. Despite the outraged protestations 
here that this is something exceptional, resorption and severe remodelling of 
cranial ornament late in ontogeny is seen in many ceratopsian clades (which, as 
marginocephalia, are the most closely related clade to pachys).

Histology is still a somewhat abstract discipline, and is barely
understood or considered by the majority of dinosaur workers. I think that you 
would
find that even dinosaur histologists like horner, padian, erickson et
al, would admit that we are still only beginning to understand how to
interpret bone histology. However, the histological evidence, as we currently 
understand it, shows that these horns are remodelling.

What I take from Horner & Goodwin, and the two talks presented at SVP that 
supported this work (which included a talk by Sullivan, a coauthor on the 
description of Dracorex) is that the dome develops through ontogeny. 
Flat-headed pachys are immature individuals. Dracorex is therefore, very likely 
not to be exhibiting adult morphology. I would not be surprised if there were 
as many as 3 definable pachycephalosaurini taxa within the Hell Creek, but I 
sincerely doubt that there were any more than one at any time. To test this 
hypothesis we need not only new specimens, but quality data to go with those 
specimens. You seem to think that there is no evidence at all to support the 
hypothesis presented by Horner & Goodwin. As it stands, the case for Dracorex 
simply being an immature Stygi is very strong. The case for separating Stygi 
and Pachy is more of a judgement call, open to either interpretation, depending 
on your inclination.



> and is going to take heaps more evidence, especially *MORE FOSSILS* (can't 
> emphasize that one enough), to demonstrate beyond reason


Feel free to push away from your computer desk and aid in the hunt for
more fossils, or make a donation to your local museum. For us, this past year
was fairly productive for pachys, and we failed to find anything that
falsified the ontogeny hypothesis. I spend over three months of every year 
digging up more specimens, or running up and down hills measuring stratigraphic 
position so that we can reanalyse old hypotheses, rather than just criticise.

Anyway, I fail to see why "diversity first" is any better a hypothesis than 
"maybe they're ontogenetic". At least people who work on ontogeny actually 
consider the diversity hypothesis. I don't see much of that happening the other 
way round.

> That is why, among other things, I was dismayed to see Longrich et al. 
> applying Horner's still-highly-controversial hypothesis to other taxa as if 
> it had already been validated(!?!?)..

It has been published, so it can be discussed. It can be accepted by people who 
write their own papers if they so feel. You might recall that it is generally 
impossible to prove anything in a historical science, only to falsify.