RE: T. rex was a 'slow-turning plodder'...

[John Hutchinson <jrhutch@rvc.ac.uk>]

Good question. I didn't check the Desmond estimates and don't have them
handy, although many of those early displacement models were not really
based on a specimen per se (except a very rough intuitive image of one). Not
sure.

The model is flexible enough that you can add as many regions of density as
you want (we could put in a whole skeleton and give it bone density), but
you gotta stop somewhere. My suspicion is that adding bones would raise leg
density a bit and lift the whole body CM a bit dorsally (toward the
vertebral column), but not much else. Sure skin, fat, air spaces, bone,
cartilage, etc all have different densities but we felt (as in all previous
studies) that respiratory spaces have the biggest effects and the others
would have smaller effects. We are testing this in the near future with
models of other animals including MRI+CT-based ones of extant animals that
will be highly detailed. We already have a few other dinos modeled too.

One of the take-home messages of the paper is that no body mass (or CM,
inertia) estimate is ever going to be perfect, and pretending we know one
single body mass value for any specimen is ludicrous; we should be looking
at ranges of possible values. That's pretty obvious but few other studies
have bothered, and many studies are based upon one body mass assumption that
is then used for growth, biomechanical, or other calculations, which is
likewise begging the question of whether the conclusions would differ
appreciably if a plausibly different mass value was input.

More interesting to me (than the rather dry paper), in a way, is the press
coverage of it. More than usual, most reporters didn't seem to RTFP, and
most did the standard approach of dichotomising the issue -- either T. rex
is hyper fast OR hyper slow (sprinter OR plodder), predator OR scavenger,
etc. Yet I think that most reasonable researchers see the real answer as a
'happy medium' -- not very fast, but fast enough; both predator and
scavenger (opportunistic), etc.  I tried to convey this but as usual the
message got amplified and simplified. Not surprising, but still
disappointing.

The most interesting experience was where a reporter speaking w/me
skeptically challenged a phrase in the paper that refers to the 'tired,
media-driven debate' about T. rex as a scavenger/predator, we spent 5-10min
discussing why this 'controversy' is BS -- just about everyone thinks it was
both! Not like we sit around conferences holding dramatic "T.rex: predator
or scavenger???" symposia"!  Then what happened? The headline was that it
was a scavenger (even though the main text refuted this somewhat). The
reporter was kind enough to contact me and apologise, his sub-editor changed
the headline from 'beast' to 'scavenger'... And the online article's
headline then had the scavenger part removed. But so much for the question
of whether the media is a big part of giving a false impression of this
'debate.'

--John R. Hutchinson 

> -----Original Message-----
> From: Sam Barnett [mailto:sam.horus@gmail.com] 
> Sent: 08 June 2007 11:37
> To: DML
> Subject: Re: T. rex was a 'slow-turning plodder'...
> 
> 
> One thing that puzzles me about this paper - they said that early mass
> estimates using scale model displacement were off because they just
> accounted for an overall volume density equivalent to water, yet in
> this experiment they used a model with 5 internal regions of 0 density
> to represent the lungs, trachea, nasal passages etc, no internal
> regions with density greater than water, but, if memory serves me
> correctly, the water displacement masses presented in Desmond's 'Hot
> Blooded Dinosaurs' were less than the 5074kg - 8405kg presented in
> this paper.  Were those earlier models based on a much smaller
> specimen?