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Re: T rex walking speed WAS: Re: Addendum to Trex vision as support for scavenging...



Phillip Bigelow (bigelowp@juno.com) wrote:

<True, but I doubt that this restriction would be a major problem for the
smallest meat eating theropods.>

  Of which *Guanlong* isn't one of. There aren't a whole lot of 1-2 meter
crested theropods save for hornbills and the like, and these tend to show how
much crevices can restrict movement for a big beaky, crested head. Not like
that's a decent parallel, of course.

<Even with bitchingly audacious head ornamentation, teeny theros' heads were
still quite small.  Even a perforation of the hide, caused by gas bloating of
the carcass, may have been large enough to accommodate a tiny theropod's head.>

  So, we're talking poking into crevices in WHAT animals? With what other
adaptations to crevice poking? In an earlier post, I mentioned that
crevice-pokers tend to have very long, slender snouts. This is true for mammals
as well as birds, and even fish (though some fish BECOME the prober, as in
hagfish, among other more or even less savory species). Crests are simply
intuitively contra the crevice-poker "archetype." And as is true of virtually
all things, there is the probability that *Guanlong* wouldn't pass up the
attempt to poke around if it could, for a nice tidbit. But if it couldn't fit a
head or a limb inside, then it couldn't eat, so the caveat has its own caveat.

<There is also the possibility that a huge sagital crest on a scavenger (be it
on a theropod or on a pterosaur) could have helped to "prop" the orifice open
while the theropod was eating.>

  Only if the structure was capable of resisting the compression of the
propping and the weight its having to move around (which also restricts its own
head's movement), which in *Guanlong* at least is unlikely given the thinness
of the bone (a few millimeters) and the likely camellate internal structure.
For comparison, even the bony casques of hornbills, which is heavily perforate
and highly camellate, retains its surface structure due to the keratin, whereas
the internal region is hollow. These animals are similarly not crevice-pokers.

<My gut feeling is that adult _T. rex's_ probably didn't "scavenge" in any
classic sense (ala hyenas or vultures).>

  You should restrict that to largely vultures, since hyenas do spend a good
deal of time hunting and are not the classic scavengers they are painted to be.

<Rather, they probably "amputated" entire sections of carcasses.  Smaller
theropods probably filled what we would today view as the commonly accepted
"scavenger niche", where many skeletal parts are left behind to be fossilized
and later studied by scientists.>

  There is some support for this, in that bite marks and isolated limbs or
limb-less bodies may indicate preferrential feeding of haunches. But
cataloguing reminds for feeding tracings would be the best way to test the
hypothesis.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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