Re: T. Rex

[larrys@zk3.dec.com]

T-rex as a scavenger has been a theory in and out of favor several times,
but my own reading is that it is basically out of consideration right now,
and likely to remain so.  The arms don't enter into it - T-rex did not
grapple with prey.  Most experts I've heard agree that this thing had one
of the most capacious and powerful bites this Earth has ever seen, the
mostly likely attack mode is a running bite that would yank half a hundred
weight of meat off the hoof, possibly compounded with a slash from the
rear talons.  This thing had _massive_ muscles and tendons, not to mention
pretty ferocious claws.  It _looks_ like a killing machine evolved to eat
large dinosaurs, and the ecosystem, as near as we can reconstruct it, would
seem to call for just such a beast.  A massive scavenger, aside from the
objections cited in Stan Friesen's post, just doesn't seem to be called for.
After all, a dead dinosaur does not object to being eaten, and smaller and
speedier scavengers would seem to have a big advantage.  They could move
faster and subsist on less - large portions of a carcass would be gone before
a rex could get there.  And, given what we can guess about lifespans, how many
carcasses would there be without T-rex to make them?  We can't depend on rov-
ing packs of velociraptors to take down an ultrasaurus, even presuming not
all of them travelled in herds.  Dienonychus is my favorite dinosaur, but even
a pack of them could not have stampeded and cut out a target for takedown out
of a herd of tricers.  The job would be tough enough for rex, though I can
easily imagine a "pride" of rexes being equal to the job.  Dinosaurs just lived
on a different _scale_.

The arms, according to computer simulations I've heard about, probably had
little to do in attack or eating.  The only use they would seem to have is
to steady the body and push it backwards when the beast rose from a lying
position.  Without them, all those massive hind legs could do would be to
push the tyro's nose along in the dirt.  The arms were large enough for that
but only just - and they were heavily muscled for their size, so they were
doing something that required some work.

Another piece of evidence cited for the scavenger theory that the original
poster didn't mention was the shallow roots of t-rex's teeth.  Of course,
the shark - which does scavenge, though it is an efficient predator overall
- also has shallowly-rooted teeth, and it isn't hindered.  I've seen specu-
lation that rex constantly renewed its teeth, so as to always have a fresh,
clean edge.  Pure scavengers would not need such teeth, even one the size
of t-rex would not need such daggers just to cut into a dead dinosaur - look
at the much smaller teeth of dinosaurs whose scavenging lifestyle is more
plausible.

I have no doubt that rex could and would partake of a free meal whenever it
found one.  But I am reminded of a "Far Side" cartoon of one vulture saying
to another "Patience, shmatience!  I'm gonna _kill_ something!"  The rex was
quite well enough equipped, methinks.

Dougal Dixon speculated in his "New Dinosaurs" that Rex might evolve into
a huge scavenger - his depiction showed a t-rex-like creature whose hind legs
had moved forward on the body to the center point, so it could stand or lie
without the forelimbs, which had withered and vanished entirely.  The result
looked like an enormous crocodile with no limbs save a pair of huge legs in
the belly area.  Not one of his most inspired ideas.

No.  Rex was a big predator that hunted really big prey.  The primeval landscape
would be just too tranquil if all he wanted was some dead meat.  To be perfect-
ly honest, I think the whole thing was dreamed up to give someone a little
notoriety by knocking down of the most legendary dinosaurs ever to reach the
public's imagination.

Larry Smith
larrys@alpha.zk3.dec.com/thesmiths@mv.mv.com