Re: PTEROSAURS: AVIAN ANCESTORS?

[Scott A Hartman <ottscay@uwyo.edu>]

>>>     Larry Dunn mentioned the scientist who claims that "naughty mice
could trip T.rex" if it ran.  If you've read Farlow's paper, I think it is
pretty clear that the "tripping mouse" drawing was a joke.  Farlow's point
was "if a multi-ton animal falls down, its going to hurt itself, so maybe
being a huge bipedal runner was kind of dangerous".  Continued resistance
to this pretty unpretentious suggestion presumably continues because
it makes T.rex look like a wuss.
     I think most of the resistance to Scott Hartman's claim regarding
feathers on _Velociraptor_ results mostly from his questionable use of
"almost certainly".  Apparently unfeathered skin impressions in at elast
some theropods make the exact distribution of integument among theropods
pretty ambiguous.  <<<

     First I'll address Farlow's paper, although this will probably start
a new thread (or an old one, as the case may be).  I certainly concur that
the cartoon was meant as a joke (and I'd guess everyone else knows it
too).  My personal resistance to the idea has nothing to do with T. rex
being wussy.  Frankly, growing up my favorite dinosaur was triceratops.  I
HATED T. rex.  But the premise in the paper isn't a good application of
physics to biology.  First of all, does everybody know what happens to a
bipedal ape when the metal container it is in crashes at 45 mph into
another metal transport?  Yet we all do it, and a surprising number of us
don't even wear seatbelts.  Of course, humans aren't a very good analogy
for Tyrannosaurs.  Instead, crunch the mass data for a white rhino.  True,
they are lower to the ground.  But if one falls on its ribs at 30 mph,
it's still a dead rhino.  This brings us to premise number two:  That T.
rex, a biped, was liable to trip.  Intuitively, as tailess bipeds, we all
know how easy it is to trip.  But in a horizontal position, with a large
tail to throw around to change your center of gravity, it's much harder.
Right after the paper came out I calculated how much kinetic energy would
be rquired to decelerate a tyrannosaur enough to trip it.  I can pull out
the numbers if any of you physics majors want them (well, after SVP I
can), but the gist of it ws that I assumed that the animal was in mid air
(harder to recover) and that it contacted an object with its metatarsals
(the further from the center of mass, the easier it is to create pitch
vectors... but high enough so that the animal couldn't just relax its toes
or raise its foot to avoid direct contact).  Basically, I made every
attempt to make 'rex go down easy.  None the less, all that kinetic energy
the animal has, which in Farlow et al's paper did in poor rexies chest, in
this situation serves to move smaller objects out of the way (essentially
"kicking them).  The results\ was a ridiculously high number of newtons
(units of force) roughly equivilent to a ten meter long tree trunk a meter
in circumference.  Probably easy enough to avoid.

Does this mean that T. rex charged around at 30 mph? No.  But it certainly
doesn't falsify the hypothesis.  Bone strength indicators have much more
potential.

Scott Hartman