Fwd: DINOSAUR digest 1275

["John R. Hutchinson" <jrhutch@socrates.berkeley.edu>]

>From: NJPharris@aol.com
>To: dinosaur@usc.edu
>Subject: Re: Dinosaur speeds
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>In a message dated 1/21/00 8:16:18 AM Pacific Standard Time,
>jrhutch@socrates.berkeley.edu writes:
>
>> However, I don't trust relative stride length [= stride length/ hip ht] as
>>  a conclusive indicator of gait.  We had elephants walking at a 2.8 RSL
>>  which according to Thulborn should be a trot (trot= 2.0 to 2.9 RSL); it was
>>  not even close.  (we presented this stuff at SICB, and I know others have
>>  recently made similar conclusions)
>
>Elephants don't trot, do they?  Elephant legs are put together rather
>differently from those of theropods (much straighter through the whole step
>cycle, for one thing), and this makes me wary of studies based on elephants
>being extrapolated to theropods.

No, elephants do not appear to trot.  At the fastest speeds recorded
empirically, they are still doing a (very fast) walk.  To a biomechanist,
"trot" and "walk" have specific meanings and are diagnosed by different
stride parameters.  An animal moving quickly is not necessarily trotting;
trotting depends on factors such as the relative phase of footfalls, duty
factor, etc.  Trotting is a "bouncing gait"(as is galloping) in which there
is potential for elastic strain energy storage in tissues; walking is a
"pendulum-like gait" in which there is little or no ESE storage but rather
potential and kinetic energy are exchanged.
        I did not say that theropods are elephants, mind you.  Nonetheless,
the trackway speed estimate principles apply whether you are an elephant,
human, theropod, or bunny wabbit, as long as you have a stride length, leg
length, velocity, and gravity.  The equations are based on more data than
just elephants.

For more discussion of elephants, there was one back in 1997 (see dinolist
archives); I don't want to rehash it.

==================
John R. Hutchinson
Department of Integrative Biology               Phone:  (510) 643-2109
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University of California
Berkeley, CA 94720-3140
http://www.ucmp.berkeley.edu/people/jrh/homepage.html