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RE: Even more concerning the Triceratops/Torosaurus deal



Brief reply:

1) My comment about the limits (or rather, the dimensions) of the 
epiparietals/-squamosals being fused to the frill result in the absence of a 
knowable placement of the suture between epiparietal/-squamosal and base frill, 
especially if the frill has undergone metaplastic growth and increased in 
length. This makes the actual dimensions (or limits) of the epis unknowable, 
simply because they do not represent measurable lengths/widths relative to the 
unfused structures. We do have unfused epiparietals/-squamosals, so we can 
somewhat measure those.

2) I noted in my reply to David Marjanovic that I was contesting the idea that 
the taxonomy implosion would result in a null hypothesis (few to one taxon to 
represent the total sample) because of ontogenetic trends that we can verify. 
No one has ever said that dinosaurs were like deer (I actually used the term 
"Bovidae," but nor were they like that, either), but that dinosaur ontogeny 
must be initially constrained by what we know of it in extant animals, and this 
is the null hypothesis. This requires that if there are sexually selected 
characteristics, then they must be progressive and not regressive even into 
late ontogeny (especially for animals that apparently had an unlimited growth 
even if it was remarkably slow and limited in size-progression in the latest 
ages).

3) I would love to see a reply to Lehman that contradicts his work without 
altering the taxonomy to do so. This is not because of any professed belief in 
the truth of Lehman's work, but because there is little to contradict it that 
does not result in either massively complex or massively simple taxonomy 
(especially under light of what the authors in this most recent work propose in 
the press about taxonomic implosion).

Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Human beings, who are almost unique in having the ability to learn
from the experience of others, are also remarkable for their apparent
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"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Sat, 31 Oct 2009 16:50:13 +0000
> From: df9465@yahoo.co.uk
> To: dinosaur@usc.edu
> Subject: Even more concerning the Triceratops/Torosaurus deal
>
> 1st note. BYU specimen was examined by Scannella. Just in case any of you 
> were concerned.
>
> I'm not addressing any questions concerning unpublished research. However 
> some discussion on Horner & Goodwin's recent paper:
>
>
>
> David Marjanovic wrote:
> <*Triceratops*, where the epiparietals and -squamosals start as pointed 
> (..."acuminate", if you prefer) osteoderms, then fuse to the skull and each 
> other, and then become broader and very blunt.>
>
> Jaime wrote:
>>Unlike in *Triceratops* where the authors propose that the epiparietal and 
>>episquamosal spikes are fused to the frill and the sutures are obliterated 
>>..... Thus the dimensions of the epis are UNKNOWABLE unlike in the spikes, as 
>>their limits are now absent. Moreover,>the determination that the gross 
>>dimensions of the epis both broaden cirrcumferentially (for want of a term, 
>>around the margin of the frill) and shrink in basoapical "length" while the 
>>metaplastic frill enlargement subsumes the bases of the epis coincidentally 
>>obliterates>the very data used to project the dimensions in the first place. 
>>These two cases are NOT analogous, even if they are both metaplastic.
>
>
> I think you need to look at some actual triceratops material. If you read 
> through horner & goodwin (2006, 2009), you will find that epis only fully 
> fuse on to the frill very late in ontogeny. Early in ontogeny they are narrow 
> and very pointed: delta shaped, and are not fused to the frill margin (hence 
> they are rarely found). Anyhow, even when the epis fuse on (or start to fuse 
> on) you can clearly see the margins of the epi in question, so the above 
> suggestion that the limits are "UNKNOWABLE" is false.
>
>
>> Moreover, the authors also project sequential metaplastic growth, then 
>> erosion, and argued that irregularities in the interface between 
>> osteoclastic and nonosteoclastic bone support this, but this can also occur 
>> with increase in invagination of the surface of the bone>via nutriating 
>> tissues and blood vessels (underlying the keratinous sheath) as they 
>> themselves argued in late-stage metaplasia. A dis
> the two types of bone, rather than regular deposition, is hardly direct 
> evidence of erosion, nor does it explain>osteoclastic bone erosion while 
> metaplasia was underway, when metaplastic transformation is to occur 
> afterward (while the structures were still apparently horn-like).
>
>
> Again, read the triceratops paper. Trike horns change orientation through 
> ontogeny, that means they ERODE bone on one side, and DEPOSIT bone on the 
> other. That's how it works.
>
>
> 
>> You know, I recall having discussions that projecting extant analogues was 
>> the only way to KNOW the constraints under which systems can work. Witmer 
>> and Holliday studying bone analogues for soft-tissues, Taylor et al studying 
>> aniaml neck posture, Hutchinson and Gatesy et als on locomotion of various 
>> tetrapods. Eliminating what doesn't work, to narrow the field to what does. 
>> Instead, the above quote purports that we can just toss in an idea because 
>> it _isn't contradictable_; tantamount to asking "why not?" This is science?
>
>
> Dinosaurs were not deer. Some people seem to have a great deal of trouble 
> accepting that fact. Modern savannah/grass based ecosystems may not be good 
> analogues for mesozoic ecology: you wouldn't compare dinosaur ecology to that 
> found in carboniferous swamps, so why do you think it is any more appropriate 
> to assume that it was similar to what we see today in entirely unrelated 
> animals? There are benefits to using comparative anatomy, of course, but 
> there are also severe limitations, and these can be very misleading. 
> Proposing comparative anatomy as the "only" way to "know" doesn't sound like 
> science to me. Anyway, if you really want a deer comparison... what age deer 
> has the best rack? Through ontogeny, (up to a point (!)) deer get more points 
> on their antlers, which are shed each year: deer don't even bother to erode 
> (=resorb) all that good phophate.
>
>
> 
> me out.>
>> I may have missed a "-al projection," which would have alluded to my 
>> understanding that ontogeny is not a proxy for phylogeny, but must derive 
>> from it nonetheless (ontogeny in the constraints created by phylogeny, 
>> whatever they are, while phylogeny will enforce by common descent similar if 
>> not identical ontogenetic trajectories as the null model). The paper 
>> proposes that it can do away with the null hypothesis by working itself 
>> backwards -- that there is a minimal number of taxa, and that metaplasia is 
>> the result of distiguishing features among age-classes. This is not to say 
>> that I prefer taxonomic profusion, and am a conservative lumper by concern, 
>> rather than practice; but simply trying to shoehorn specimens into an 
>> ontogenetic scheme and say that the ontogenetic scheme supports the 
>> shoehorning is certainly not a safe ground.
>
>
> Why is taxonomic diversity the null hypothesis? Frankly, 
> always-cladogenesis/diversity is unfalsifiable, therefore unscientific. 
> There's a lot of good data that corroborates Horner & Goodwin's views, but 
> you will have to wait for the paper. Dinosaur taxonomy as we know it, is 
> going to change.
>
>
>> I would suggest looking up the work Lehman has done to clarify the taxonomic 
>> disparity among different areas in similar ages of the latest Cretaceous. It 
>> was certainly not one "narrow strip of forested floodplain," and we are 
>> cautious about assuming that all taxa recovered where we have originated in 
>> that region. Simply examining the veldt or Serengheti will provide a 
>> diversity of Bovidae in what is "just one big savannah," by comparison.
>
>
> See my above comment. I have presented at SVP on why most of what Lehman 
> published on the biogeography issue is incorrect. Adherence to these old 
> views holds back our understanding of what is going on. You'll see much more 
> on this issue presented and published over the coming few years.
>
>
>
                                          
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