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



Denver Fowler [df9465@yahoo.co.uk] 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.
>
>>>>>>>>>>>>>>>>>>>>>>>>>>

Pretty much the last sentence says it all, we are still trying to understand 
the implications of their work and it is not at all how "we" currently 
understand it, it is how Horner et al. interpret it and there will be a long 
set of discussions - with much more work needed - before we have a model that 
is generally accepted - including for ceratopsians - which is as it should be 
in science. No one is suggesting that Horner et al. are full of crap - Jack's 
an old friend I admire a great deal - just that they have provided a model that 
must be tested, etc. a lot more and requires much much much more data before we 
get to the "we" stage. And this is not in any way a negative blast towards Jack 
and Mark.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

> 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. 

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Well yeah

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

>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.


>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Sorry but we are nowhere near the point of work where we can suggest that all 
flat-headed pachys that are or will be found were immature given all sorts of 
possible developmental mechanisms related to heterochrony, developmental 
mechanisms related to dimorphism, etc, and individual variation that can be so 
high in presumably social animals. Draco may indeed be a juvenile but that also 
doesn't make it necessarily a juvenile of pachy - this will take far stronger 
phylogenetic work than has been done or can be done right now, and, surprise, 
much more material. Further, morphological interpretations in continuously 
growing reptiles are much trickier than in mammals, so documenting relative 
ontogenetic positions for different specimens can be amazingly tricky, 
especially with small sample sizes.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

>> 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.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


This was just wrong and condescending and assumes a knowledge of the activity 
(or lack thereof) of others you just have no way of really knowing or 
dictating, frankly. Out of line.

I would suggest you spend less time summarily accepting early-stage hypotheses 
of others and spend more time developing your quantitative toolboxes so you can 
contribute to the long-term theoretical discussions better.


Ralph Chapman