RE: Another PLoS One comment

[Jaime Headden <qi_leong@hotmail.com>]

  This response doesn't appear to account for the recent revisions in 
estimating masses of particular muscles, especially the mCFL (Mallison, 2010, 
2011; Persons & Currie, 2011a,b). Such estimates for some taxa are woefully 
under-estimated, and this can be accounted for by over-leaning the bodies. Your 
reply does not mention these analyses, possibly because, as Hutchinson et al. 
(2011) state, some are based on fitting skin to a near-skeletal model of a 
tyrannosaur, something that is akin to the modeling proposed by Paul (2000). 
The mCFL represents by itself a substantial amount of mass in the body and 
influences CoG and thus walking/running motion dynamics and mass directly. Even 
if Hutchinson's robust mass estimates, using a "inflated" envelope around the 
body, are massively over-proportioned, one can take the numbers used to 
generate the envelope and slim it down directly; this cannot be done with the 
sculpted-model/immersion technique favored by Paul, which also introduces a 
massive amount of bias which can produce error. Computational analyses, as in 
Hutchinson, Mallison, Persons, and Allen's works, produce estimates based on 
mathematic models, and can be directly tweaked, but one must _estimate_ the 
relative mass in a clay or plastic model for the immersion technique, and 
revise the physical model itself, compounding human bias in the error margin. I 
think it is (and has been) far beyond the time to retire the immersion model as 
useful when far better, more precise and easily adjustable, methods exist to 
estimate mass.

Allen, V., Paxton, H. & Hutchinson, J. R. 2009. Variation in center of mass 
estimates for extant sauropsids, and its importance for reconstructing inertial 
properties of extinct archosaurs. _The Anatomical Record_ 292:1442–1461.
Hutchinson, J. R., Bates, K. T. & Allen, V. 2011. *Tyrannosaurus rex* redux: 
*Tyrannosaurus* tail portrayals. _The Anatomical Record_ 294:756-758.
Mallison, H. 2010. The digital *Plateosaurus* I: body mass, mass distribution, 
and posture assessed using CAD and CAE on a digitally mounted complete skeleton.
_Palaeontologia Electronica_ 13(2):8A.
Mallison, H. 2011. Defense capabilities of *Kentrosaurus* aethiopicus Hennig, 
1915. _Palaeontologia Electronica_ 14(2):10A.
Paul, G. S. 2000. Limb design, function and running performance in 
ostrich-mimics and tyrannosaurs. _Gaia_ 15:257–270.
Persons, W. S., IV & Currie, P. J. 2011. The tail of *Tyrannosaurus*: 
Reassessing the size and locomotive importance of the M. caudofemoralis in 
non-avian theropods. _The Anatomical Record_ 294:119-131.
Persons, W. S., IV & Currie, P. J. 2011. Dinosaur speed demon: The caudal 
musculature of *Carnotaurus sastrei* and implications for the evolution of South
American abelisaurids. _PLoS ONE_ 6(10):e25763.

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)


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> Date: Fri, 20 Jan 2012 09:24:01 -0500
> From: gsp1954@aol.com
> To: dinosaur@usc.edu; vrtpaleo@usc.edu
> Subject: Another PLoS One comment
>
>
> I've posted another comment on Tyrannosaurus mass estimates addressing a 
> number of issues at
>
> http://www.plosone.org/annotation/listThread.action?inReplyTo=info%3Adoi%2F10.1371%2Fannotation%2F7082d67e-9835-49bc-ad62-2b330753c355&root=info%3Adoi%2F10.1371%2Fannotation%2F7082d67e-9835-49bc-ad62-2b330753c355
>
> I was quite surprised to realize that the Henderson & company mass estimates 
> based on my skeletal restoration of 5027 were much higher simply because they 
> increased the size of models.
>
> GSPaul