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



Denver Fowler said:

>Yes but the point is that you seemed to claim that the skull was fake,
>when the truth is that you clearly didn't know whether it was or not.

The actual truth: I was 99.9% certain that the skull was fake. I could have bet 
serious money that it was. Especially considering that there are many totally 
fake _Stygimoloch_ skulls out there in museums and so forth, and this one 
looked enough like them to be deceptive - and the description on Wikipedia 
stated that the skull was 'reconstructed', not 'partially reconstructed' or 
anything of the sort.

My bad. My bad. My bad. My bad.

>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.

>I think if you read back through your comments you'll find that there is
>plenty of mocking tone, and suggestions that Jack's work is rarely any
>good. Do you think if Horner and Goodwin read your comments they'd see
>them as fair criticim, or snarky side-swipes? Some of your comments, and
>those of other people, have ridden very close to the line.

I've read back through the comments and can't find much of anything that could 
realistically qualify as such. Any mocking tone or snarky side-swipes in my 
posts (at least) are not intentional, but are rather the product of the 
reader's interpretations. One can read/interpret a comment any way they wish, 
it does not mean that anything that they get out of it was done on purpose.

>And anyway, you're completely missing the point of the paper. Before this
>study, people thought that flat-headed pachys were adults, and potentially
>completely separate clades from domed forms, hence the convoluted comment
>in the Dracorex description about comparing bowling balls etc.. The work of
>Goodwin and Horner has shed some doubt on this orthodoxy, suggesting that
>non-domed forms might be immature.

No, I complete get the point of the paper - that the dome develops through 
ontogeny, that flat-headed pachys are not separate taxa but rather are immature 
individuals of dome-headed pachys, and that _Dracorex_ is (or is likely to be) 
a juvenile _Pachycephalosaurus_. My point, among other points, is that I have 
yet to see strong evidence that the flat-headed pachys are juveniles. The 
publication of Horner and Goodwin's hypothesis aside, next to nothing has 
changed from the time that flat-headed pachys were widely considered as 
separate taxa until now. It's not like any spectacular new fosils demonstrating 
the ontogenetic transition from flat-headed and 'supratemperal fenestraed' to 
dome-headed and 'supratemporal fenestrate-less' have been found. And 
circulating rumors that fully-domed baby _Pachycephalosaurus_ skulls (or skull 
material) have been found at the Sandy Site in South Dakota and are awaiting 
further study certainly do not make the hypothesis that the flat-headed pachys 
are juveniles any easier for skeptics such as myself to except.

David Marjanovic said:

>> Is this true in the case where the horns are also rapidly enlarging?
>> It would seem in that case that merely increasing deposition on one
>> side would change curvature w/out any removal required.
>
> That would result in an S-shaped horn, and that's not what we see.
> Instead, the horns first curve backward, then they stick straight up,
> and then they curve forward.

I don't know how relevant this is, but there are a few _Triceratops_ skulls 
that show S-shaped horns. Perhaps the best example is that of the type of 
_Triceratops prorsus_, which is the skull seen on Marsh's original skeletal 
reconstruction:

http://dic.academic.ru/pictures/wiki/files/116/triceratops_prorsus_old.jpg

An attractive illustration of the skull forms Plate XXXIV of Hatcher et al. 
1907.

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...?

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.

*My counter-argument was that the sample size of extant archosaurs is too small 
to be able to state seriously that venom is unusual in archosaurs. Note that 
this argument, if it ever even held water at all, would not apply here, because 
while we don't have any extant archosaurs with venomous bites we *do* have 
related clades such as lepidosaurs that contain just such venomous members. 
This case is different because we do not find Hornerian growth even when we 
exit the realm of extant archosaurs. We actually have to get as basal as FISH 
before finding it, which is still weird no matter how you slice it.

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_ontogeny.png

I know Bakker et al. 2006 noted it, but it doesn't seem to have received much 
attention otherwise. It's clear that pachycephalosaurid systematics is in a 
total state of confusion, and that there appears to be something weird going 
with Hell Creek pachys - I'm just not (yet) convinced that the flat-headed 
pachys are juveniles of dome-headed taxa, nor do I beleive that Horner and 
Goodwin have provided sufficiant evidence to support their case (yet).

~ Michael

----------------------------------------
> Date: Sun, 10 Jan 2010 21:45:43 +0000
> From: df9465@yahoo.co.uk
> To: dinosaur@usc.edu
> Subject: Re: Horner's Pachy Lumpin' - Your Thoughts?
>
>
>
>>Sorry Michael but the important parts of that skull, i.e the squamosals,
>>perietals, frontals, dome, spikes, etc are all real. Only the face and
>>snout are reconstructed.
>>>Okie dokie then. It's real. That's fine.. But I actually don't see any more 
>>>than three squamosal horns in that picture anyway.
>
> Yes but the point is that you seemed to claim that the skull was fake, when 
> the truth is that you clearly didn't know whether it was or not. We have a 
> cast of the photographed specimen (the real part, not the
> mocked up complete thing). It's a nice fronto-parietal dome, with the
> squamosals etc complete at the back. It was observed for the Horner
> Goodwin study.
>
> 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)? You might be surprised to see what the fossils actually show.
>
>
>>I find it most interesting that you are so quick to make ad hominem
>>attacks against Horner and Goodwin
>>>Okay, the record needs to be set straight. First, I have never made any ad 
>>>hominem attacks against Horner or Goodwin (nor have I seen anyone else do 
>>>so).
>
> I think if you read back through your comments you'll find that there is 
> plenty of mocking tone, and suggestions that Jack's work is rarely any good. 
> Do you think if Horner and Goodwin read your comments they'd see them as fair 
> criticim, or snarky side-swipes? Some of your comments, and those of other 
> people, have ridden very close to the line.
>
>
>>Overall, as others have said, I think the best way (in fact, in a
>>scientific sense, the *only* way) to refute Horner &c's hypothesis is to
>>assemble data that supports an alternative hypothesis
>>>First I'd like to see strong data assembled that supports *their* 
>>>hypothesis. I'm with Ralph in that I find it odd how Horner's hypothesis, 
>>>still in its early>>stages and in need of a lot more testing, etc. is being 
>>>taken as The Real Truth and the burden is considered to have swiftly and 
>>>automatically shifted to>>other models.
>
> The term "trut
> d the paper (and know maybe a little bit about histology) can form their own 
> opinions, and it would seem that most pachy workers seem to quite like the 
> idea that flat-headed forms are immature. They might be wrong, sure, but 
> that's science. I just think Longrich et al were playing on "what if Horner & 
> Goodwin are right, how would that idea fit into our model". You seem to be 
> suggesting that they shouldn't even consider this, but that apparently, it is 
> much more acceptable to take the approach that everything is a separate 
> species until "proven" (somehow) otherwise.
>
> And anyway, you're completely missing the point of the paper. Before this 
> study, people thought that flat-headed pachys were adults, and potentially 
> completely separate clades from domed forms, hence the convoluted comment in 
> the Dracorex description about comparing bowling balls etc.. The work of 
> Goodwin and Horner has shed some doubt on this orthodoxy, suggesting that 
> non-domed forms might be immature. It would not be surprising to me if 
> Dracorex and Stygimoloch might be conserved as separate taxa (at least at the 
> species level) in the future, but it will not be based on the presence or 
> absence of a dome (shape of dome: the jury is still out).
>
>
>
>
----------------------------------------
> Date: Sun, 10 Jan 2010 22:52:01 +0100
> From: david.marjanovic@gmx.at
> To: dinosaur@usc.edu
> Subject: Re: Horner's Pachy Lumpin' - Your Thoughts?
>
>> Is this true in the case where the horns are also rapidly enlarging?
>> It would seem in that case that merely increasing deposition on one
>> side would change curvature w/out any removal required.
>
> That would result in an S-shaped horn, and that's not what we see.
> Instead, the horns first curve backward, then they stick straight up,
> and then they curve forward.
>
>> Further -- I wonder if backwards curving horns in juveniles is
>> mentioned in lit as support (on a selective basis) for the 'extended
>> close physical adult/offspring contact' scenario. Perhaps hunkering
>> underneath Mom for protection from sun, weather, and predators (etc)
>> was better tolerated by Mom if your little horns did not stick
>> STRAIGHT up... :D
>
> Who knows! :-)
>
> Regarding horn resorption in *Pachyrhinosaurus*, this looks to me like
> the horn core was resorbed while the keratinous horn stayed;
> counterintuitive enough, but perhaps it suggests the same for
> *Pachycephalosaurus*.
>
>
>
>
----------------------------------------
> Date: Sun, 10 Jan 2010 15:32:57 -0500
> From: tholtz@umd.edu
> To: david.marjanovic@gmx.at
> CC: dinosaur@usc.edu
> Subject: Re: Horner's Pachy Lumpin' - Your Thoughts?
>
>
> David Marjanovic wrote:
>
>
>> It is absolutely counterintuitive that an animal would first grow horns
>> and then shrink them to fairly blunt knobs. But, on a smaller scale, the
>> same thing happens to the "epoccipitals" of ceratopsids (which I frankly
>> expect to turn out one day to be homologous to pachycephalosaur spikes).
>> Perhaps more importantly, the horns of *Triceratops* (even when
>> *Torosaurus* is not included) _change curvature_ during ontogeny, from
>> backward-pointing to forward-pointing. The only way to change the
>> curvature of a bone is to deposit bone on one side and _remove it_ from
>> the other. Here we have the large-scale absorption the pachy-lumper
>> scenario requires.
>>
> Another ceratopsid case of metaplasia: the postorbital and nasal horns of
> young 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.
>
> --
> 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
>
>
----------------------------------------
> Date: Sun, 10 Jan 2010 17:38:58 -0800
> From: d_ohmes@yahoo.com
> To: dinosaur@usc.edu
> Subject: Re: Horner's Pachy Lumpin' - Your Thoughts?
>
> -- On Sun, 1/10/10, David Marjanovic wrote:
>
>>> Is this true in the case
>> where the horns are also rapidly enlarging?
>>> It would seem in that case that merely
>> increasing deposition on one
>>> side would change curvature w/out any removal
>> required.
>
>> That would result in an S-shaped horn, and that's not what
>> we see. Instead, the horns first curve backward, then they
>> stick straight up, and then they curve forward.
>
> An S-shape? Not necessarily, in the case where diameter is increasing as well 
> as length. The "old" curve can be easily swamped, at least in trees, by 
> asymmetrical diameter growth. It is still there, but is buried underneath new 
> growth.
>
> Curvature reversal is often seen in logs. Lengthwise slicing along pith 
> center brings it out nicely (personal obs.).
>
> However, who cares? Curvature reversal is not needed to prove the resorption 
> case as mentioned by others previously.
>
>>> Further -- I wonder if backwards curving horns
>> in juveniles is
>>> mentioned in lit as support (on a selective
>> basis) for the 'extended
>>> close physical adult/offspring contact'
>> scenario. Perhaps hunkering
>>> underneath Mom for protection from sun, weather,
>> and predators (etc)
>>> was better tolerated by Mom if your little horns
>> did not stick
>>> STRAIGHT up... :D
>
>> Who knows! :-)
>
> Heh. Well, somebody probably does. Note I asked if the (I assume untestable) 
> concept is mentioned in print, not if it actually occurred.
>
>> Regarding horn resorption in *Pachyrhinosaurus*, this looks
>> to me like the horn core was resorbed while the keratinous
>> horn stayed; counterintuitive enough, but perhaps it
>> suggests the same for *Pachycephalosaurus*.
>
> Stressing I have NO opinion re lumping/splitting, etc, I do not find horn 
> size reducing w/ age, or even disappearing entirely, to be particularly 
> "counter-intuitive". Taking a case where the horns and frill are assumed to 
> be defensive in function* (for example), it could imply a "social" structure 
> wherein older animals were not active in
> ng to herd center or even being outcast, perhaps depending on reproductive 
> assumptions.
>
> 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? Lack of extant analog isn't a very strong argument, barring some 
> apparent violation of physical laws.
>
> *I note that the frill is intimidating in appearance, especially from the 
> front view, even if it has no real function as armor.                         
>                 
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