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RE: Protoceratops juvies, unfenestrated parietal (repost)



  The argument differs, though. 

  In "Triceratops," Scannella and Horner infer the fenestrae open _only_ during 
adulthood, discretely classifying a "young adult" above the "subadult" stage 
which acheived adult size and frill characteristics, no fenestrae, but are not 
"old adult" which is reserved for specimens ascribed to *Torosaurus latus* and 
*gladius*. 

  Fenestrae appear to develop in *Protoceratops andrewsi* in a larger range of 
sizes, in skulls <1/3 the size of the largest. For example, Dodson, 1976, 
demonstrates parietal fenestrae in specimens as small as AMNH FR6419 (total 
lenghth 76mm), while other specimens at >300mm also bear fenestrae. This is 
argued to have a low variability for the twelve specimens sampled for this 
particular variable. While Dodson was expressly focusing on sexual dimorphism, 
the logs are all-inclusive for length to fenestrae and length to frill, which 
are concordant. The relative size of the fenestrae in the parietals in 
*Protoceratops andrewsi* do not appear, in this small sample, to be relevant in 
_late_ ontogeny, which was Scannella and Horner's argument for "Triceratops." 

  Based on the photo below, the skulls of these juveniles appear to be about 
50mm, so smaller than the smallest specimen Dodson sampled, and thus the 
assertion that fenestrae appear "somewhere post-hatching ontogeny" can be true, 
but the arguments for any sort of comparison is problematic. Why did the frill 
open up so extremely late in *Triceratops horridus* or *prorsus* ontogeny? 
That's a better question to answer to stave off the critics of the argument 
that open-frilled ceratopsians in the Hell Creek and equivalent are the same as 
close-frilled ceratopsians. But it certainly wasn't the same timing as 
*Protoceratops andrewsi*, and it doesn't tell us why virtually all other 
[relatively complete] chasmosaurine and centrosaurine frills have fenestrae 
(this is especially true when you consider the sample sizes of specimens of 
*Pachyrhinosaurus lakustai* including frills under half the size of adults and 
indicating widely-open fenestrae.

Dodson, P. 1976. Quantitative aspects of relative growth and sexual dimorphism 
in *Protoceratops*. _Journal of Palaeontology_ 50(5):929-940.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

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


"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: Fri, 11 Nov 2011 16:58:48 +0000
> From: df9465@yahoo.co.uk
> To: dinosaur@usc.edu
> Subject: Protoceratops juvies, unfenestrated parietal (repost)
>
>
>
> Fortunately the previous version of this message got truncated 'cause it was 
> sent unfinished, by accident
>
> ----- Forwarded Message -----
> From: Denver Fowler <df9465@yahoo.co.uk>
>
> So here's an interesting quote from a new paper by Fastovsky et al (not 
> mentioned so far):
>
> Fastovsky, D., Weishampel, D., Watabe, M., Barsbold, R., Tsogtbaatar, K., &
> Narmandakh, P. (2011). A Nest of Protoceratops andrewsi (Dinosauria,
> Ornithischia) Journal of Paleontology, 85 (6), 1035-1041
>
> "Fenestrae are not developed in the frills of these
> juveniles, although they become well-developed in adult
> Protoceratops."
>
> Blog posting:
> http://blogs.smithsonianmag.com/dinosaur/2011/11/at-last-a-true-protoceratops-nest/
>
>
> When do parietal fenestrae form in Protoceratops? somewhere post-hatching 
> ontogeny. The same as Triceratops.
>
>
> ----------------------------------
> Denver Fowler
> df9465@yahoo.co.uk
> http://www.denverfowler.com
> -----------------------------------