[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: bipedal lunges

John Clavin (sorry for screwing up your name) wrote:

>Most creatures are vulnerable to attack from behind - nothing unusual
>What if the triceratops used an aggressive defense - i.e. once it
>figures out there's a threat, it takes action rather than try to ignore
>it and rely on a passive defense. 

Cruel youth! You pursue me even in defeat and ignominious concession!  So,
like our conjectural tetrapod, I must turn at bay ...

Of course the ceratopsian must rely on an active defense.  Its not an
ankylosaur.  It can't pretend to be a rock, nor, in all likelihood, can it
bound over the horizon like a Brobdignagian gazelle.  Furthermore, the very
size of most dinosaurs suggests that each individual represented a
substantial metabolic investment by the species.  Thus it is likely that the
defense of each individual was a significant matter.  The question on the
table is HOW the beast could mount such a defense.

The major constraint on ceratopsian defense was that the head represented
both the best defensive structure and the only significant offensive
armament (horns, if any, and beak).  The most parsimonious solution is that
it did not normally present any other front to predators.  It could have
done so by threading its way, snake-like through rocky hills or primeval
forests; but this is pretty unlikely for a big low-browser.  Herd-based
defense is a more reasonable way to accomplish this purpose and places our
protagonists on the plains or the forest margin -- a more logical
mise-en-scene for their probable ecological niche.

OK.  We've circled the wagons.  The tyranosaur is pacing about outside the
circle with beady eye and slavering jaw.  What do we do now, boss?  The
predator might be overcome with ennui and wander away.  Probably happened
that way as often as not.  But the circle is small and irregular, not packed
shoulder to shoulder (I leave the reason for this as an exercise for the
reader -- I'm late for work).  The predator is likely to see a gap or
misplacement before long, even if it works alone.  The ceratopsian must have
a way to present a credible threat as well as a credible defense.

It can't charge for several reasons.  Badly designed for this: front legs
too short.  Bad tactics: destroys the defensive formation and exposes itself
to lateral attack from a second predator.  Relative speed: the bipedal
therapod predator is likely to be quicker and more agile and so avoid damage.

It can't wait for an angle.  This lets the attacker choose the the time,
place and approach.  Poor tactics.

What are we left with?  Some sort of short lunge.  Temporary bipedalism
could give the defender the maximum choice of target.  But there are a few
other possibilities, like gathering weight on the rear legs for a sort of
brief pounce (imagine a four ton cat).  Somehow, its got to get its most
dangerous feature, the beak, near the predator's most vulnerable features,
probably leg tendons, without unduly exposing the ceratopsian flank or the
other members of the group.  This doesn't leave a whole lot of options.

This is a long chain of probabilities, and subject to all the infirmities of
such a chain.  However, you need to give me an alternative which is at least
as plausible.

There. I've mounted my own counter-offensive.  Must I continue threat
displays, or may I go back to chewing grass?

  --Toby White