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



First I would like to say that while I consider my arguments to be sound and 
well-grounded, looking through a few posts again, this time I can see where 
some of my comments toward Horner and Goodwin 2009 were much too hostile or 
snarky or both. An aggressive assault on the authors (or the paper) was not my 
intention, but that is definitely what it came out as, and I am glad that I 
looked back through the posts one more time so that I could recognize this 
problem for myself and take this opportunity to apologize. So.. . Apologies.

Moving on, Tom Holtz wrote:

> http://www.dinosaures-web.com/images/dino/triceratop_horns.jpg

Well, it's true that that particular adult _Triceratops_ has horns that are 
just about exactly the same size as the subadult's. However, Most _Triceratops_ 
adult skulls I've seen have bigger horns than that - I wonder if that 
individual's horns are abnormally short. (?)

>Currie, P. J., Langston, Jr., W., Tanke, D. H., 2008. A New Horned Dinosaur
>from an Upper Cretaceous Bone Bed in Alberta. NRC Press. 152pp. ISBN-13
>9780660198194.
>
>SCOTT D. SAMPSON, MICHAEL J. RYAN & DARREN H. TANKE. 1999. Craniofacial
>ontogeny in centrosaurine dinosaurs (Ornithischia: Geratopsidae): taxonomic
>and behavioral implications. Zoological Journal of the Linnean Society.
>121: 293-337

Thanks!

> All that being said, an actual adult Dracorex specimen or a juvenile
> Pachycephalosaurus that isn't Stygimoloch and/or Dracorex would end this
> debate really damn quick.

Hmm...
 
http://www.wmnh.com/wmtr15.htm
 
http://www.rmdrc.com/news/RMDRC_newsletter_0808.htm

The problem is that these things, if they're really what they say they are, are 
not getting published on. Hopefully they're under study.

~ Michael

----------------------------------------
> Date: Mon, 11 Jan 2010 14:23:29 -0500
> From: tholtz@umd.edu
> To: tehdinomahn@live.com; dinosaur@usc.edu
> Subject: RE: Horner's Pachy Lumpin' - Your Thoughts?
>
>> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]
>> On Behalf Of Michael Erickson
>>
>>>You also made claim that Triceratops horns are longest in adults. Do
>>>you know this for certain? How many Triceratops skulls have
>> you looked
>>>at (even in photos)?
>>
>> Tons, as _Triceratops_ is one of my favorite dinosaurs. I
>> have never seen a young individual with horns bigger than an
>> adult's, if anyone else has feel free to point it out.
>> Everything I've seen indicates that the horns are biggest in
>> adults and very late subadults.
>
> http://www.dinosaures-web.com/images/dino/triceratop_horns.jpg
>
> That said, a scatterplot of a lot of skulls would be very nice... (Thanks
> for the shoutout, Ralph!)
>
>> Tom Holtz wrote:
>>
>>>Another ceratopsid case of metaplasia: the postorbital and
>> nasal horns
>>>ofyoung Pachyrhinosaurus are indeed horns, but as they aged the
>>>postorbital horns get resorbed and remodeled into pits and the nose
>>>horn into the distinctive mound.
>>
>> I've heard a lot about this but can never find a reference. Anyone...?
>>
> Currie, P. J., Langston, Jr., W., Tanke, D. H., 2008. A New Horned Dinosaur
> from an Upper Cretaceous Bone Bed in Alberta. NRC Press. 152pp. ISBN-13
> 9780660198194.
>
> SCOTT D. SAMPSON, MICHAEL J. RYAN & DARREN H. TANKE. 1999. Craniofacial
> ontogeny in centrosaurine dinosaurs (Ornithischia: Geratopsidae): taxonomic
> and behavioral implications. Zoological Journal of the Linnean Society. 121:
> 293-337
> (http://www3.interscience.wiley.com/cgi-bin/fulltext/120802209/PDFSTART)
>
>> Don Ohmes wrote:
>>
>>>There may not be an extant analogue, but so what? Is there a
>> dinosaur
>>>that grew annual antler-analogs? Should we assume one existed, just
>>>because we now have elk?
>>
>> That's a weak argument right there. No one has even compared
>> dinosaurs to mammals until you just did. I totally ignored
>> mammals, actually, focusing on reptiles and birds. But
>> anyway, I think that the fact that no extant organism more
>> derived than a fish seems to grow in such a manner is a bit
>> too weighty an argument to be cast off automatically. It's
>> not conclusive, to be sure, but it is suggestive (just how
>> suggestive is open to debate, but still).
>>
>> I find that the EPB has been pretty much ignored in this
>> discussion, something I find peculiar. Just a few weeks ago
>> many were stating that it is most parsimonious to conclude
>> that _Sinornithosaurus_ did not posess a venomous bite, based
>> on the EBP*. Why doesn't it apply here? Why isn't it most
>> parsimonious to conclude that pachycephalosaurids did not
>> grow in this manner, considering that no extant reptile or
>> bird does? Is it because Horner and Goodwin's arguments are
>> considered conclusive enough to trump parsimony? If so, then
>> I would beg to differ, of course.
>
> The EPB is used for inferring traits otherwised not observed and for showing
> the relative support for inferring these traits (level I: both members of
> the bracket have it; level II: only one does; level III: neither do). It is
> NOT a guide to utterly exclude traits in the fossil form, particularly if
> other lines of evidence (such as histological ones) apply.
>
> And the Erickson et al. papers and their spin offs HAVE demonstrated that
> there are peculiarities of growth in Mesozoic Dinosauria that are not
> present in Mammalia, Testudines, Lepidosauria, Crocodylia, and living Aves.
>
>> Has anyone else on the list noticed that _Stygimoloch_ is
>> exactly the same size as _Dracorex_?:
>>
>>
> http://upload.wikimedia.org/wikipedia/commons/0/05/Pachycephalosaurus_ontoge
> ny.png
>>
>> I know Bakker et al. 2006 noted it, but it doesn't seem to
>> have received much attention otherwise.
>
> Actually, doi:10.1371/journal.pone.0007626.t001
>
> All that being said, an actual adult Dracorex specimen or a juvenile
> Pachycephalosaurus that isn't Stygimoloch and/or Dracorex would end this
> debate really damn quick.
>
> Thomas R. Holtz, Jr.
> Email: tholtz@umd.edu Phone: 301-405-4084
> Office: Centreville 1216
> Senior Lecturer, Vertebrate Paleontology
> Dept. of Geology, University of Maryland
> http://www.geol.umd.edu/~tholtz/
> Fax: 301-314-9661
>
> Faculty Director, Earth, Life & Time Program, College Park Scholars
> http://www.geol.umd.edu/~jmerck/eltsite/
> Faculty Director, Science & Global Change Program, College Park Scholars
> http://www.geol.umd.edu/sgc
> Fax: 301-314-9843
>
> Mailing Address: Thomas R. Holtz, Jr.
> Department of Geology
> Building 237, Room 1117
> University of Maryland
> College Park, MD 20742 USA
>
>                                         
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