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Re: Still not a happy camper

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.


--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.