Re: Still not a happy camper

[Michael Habib <mhabib5@jhmi.edu>]

In fact, the Compsognathus speed estimate is just the most obvious part 
of an overall trend (found by Sellers and Manning) that seems to be 
clearly erroneous.  Namely, they found a near-linear inverse 
relationship between body mass and speed.  Having gone over the methods 
fairly quickly thus far, I have yet to find where this result is likely 
to have come from.  Regardless, it seems to me that some parameter fed 
to the evolutionary algorithm resulted in the model "expecting" mass to 
predict speed in a linear fashion (which is dubious to start with), and 
in an inverse manner (which is even worse).  Obviously, the smallest 
animals do not have the highest absolute speeds, so something is awry.  
We might expect the smallest theropods to have the highest relative 
speeds of the group, and I wonder if there was a glitch somewhere that 
ended up translating high relative speed into exceptional absolute 
speed estimates.

Cheers,

--Mike H.


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu


On Thursday, August 23, 2007, at 07:26  PM, GSP1954@aol.com wrote:

> The Sellers and Manning paper makes it clear that the modeling of 
> animal
> locomotion still has a long way to go before it produces reliable 
> results. As
> Hutchinson told a reporter, the claim in S&M that Compsognathus was 
> extremely fast
> is clearly errant. It is not possible for animals much smaller than 
> cheetahs
> and pronghorn to run at very high speeds because they lack 
> sufficiently long
> legs to achieve the very long strides needed to move as very high 
> speeds --
> there is no way a kangaroo rat for example, much less a cockroac, can 
> run 35 mph.
> With its big tail trailing behind and modest length legs little Compy 
> was
> probably little or no faster than a chicken.