read and learn

["Colette H. Adams" <cadams@hh.gpz.org>]

Greg, you're priceless.  The man knows his shit, boys and girls.  Read and
learn.  Incidentally, I'm ordering another copy of Predatory Dinosaurs of
the World to replace one I gave to a young friend of mine.  It is only the
second book I've bought this year.  On $5.45/hr I am very choosy.

Other than that I will continue to remain silent on the bioenergetics issue
for now.

Here's a can of worms I actually would like to open.  On many occasions I
have heard it suggested that ceratopsians would have turned on their
attackers and used their horns for defense rather than flee.  Forgive me,
both those who suggest such a thing do not understand natural selection.
Let's imagine we have a herd of ceratopsians.  A tyrannosaur shows up.
Some of the ceratopsians have the "run like hell" gene.  Some of them have
the "turn and defend" gene.  Now who do you think will be passing their
genes to the next generation?  Natural selection will ALWAYS favor "run
like hell."  If the ceratopsian cannot flee, then of course it will defend
itself however it can.  But it will always go for the flight option first.
Triceratops horridus did only one thing when it saw, heard, or smelled
Tyrannosaurus rex.  It ran like hell.

Some have made much of the dangers of large theropods falling.  This is
supposed to limit their ability to grapple with large prey.  I agree that
the danger is there.  I also feel strongly that some have underestimated
the sense of balance these animals had.  Think of how difficult it would be
to knock an ostrich over.  Yet an ostrich has only a short, light tail and
a pair of stubby wings to help it stay up.  Big theropods, with the large,
muscular tails, must have been absolute masters at staying erect.  This is
even more true of tyrannosaurs, which could support virtually no weight on
their forelimbs.

My point is that with large theropods, tyrannosaurs particularly, we are
talking about animals of enormous power, balance, and weaponry.  Some
people look at their bulk and seem to think it was all fat.  I note also
that some have looked at the teeth of tyrannosaurs and concluded that they
were not very sharp, thus inadequate for slashing.  The wheels of a
locomoative aren't very sharp, but I wouldn't recommend that you go to
sleep on the railroad track.  To suggest that big theropods had some
difficulty killing prey just because it was large, or had horns, or
whatever, is goofy.  Even a small tyrannosaur, say polar bear sized, would
be a tremendous danger to the biggest ceratopsian.

I am less confident about exactly what strategy tyrannosaurs used to kill.
Tom Holtz and others have suggested that they fall into the pursuit and
bite category, typified by large canids.  But it is difficult for me to
envision a tyrannosaur-ceratopsian chase through forest.  I find it more
plausible that large theropods used a Komodo dragon type strategy, waiting
along animal trails and lunging out at their prey as it passed by.  They
slashed horrific wounds, then followed their prey until it succumbed.  I
believe the reason tyrannosaurs are so gracile is that it does little good
to slash a ceratopsian and then track down its corpse if someone else gets
to it first!  This is exactly the problem Komodo dragons face.  Having
cursorial adaptations allows you to move quickly at greater energy
efficiency, thus reaching your kill before the other tyrannosaurs can.  I
believe this is what drove selection for cursorial adapations in tyrannosaurs.

Wasn't that a happy little story?

Best regards,

Dave