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Re: a little background



On Sun, Mar 10, 2002 at 10:10:07AM +0100, David Marjanovic sent:
> > (My own suspicion is that the theropod mass models are badly out of
> > whack; I will cheerfully believe in large theropods with half their body
> > mass in their legs, and have the suspicion that the apparent general
> > size limit for that body plan may be at a much lower mass point that
> > hitherto suspected.)
> 
> I tend to agree because the longer they are looked at, the more pneumatic
> they appear to be, yet still pretty high densities are normally used to
> calculate mass from volumetry. I also think the forward-falling method
> should be looked at mathematically (of course, this asks for another work of
> that size...).
> 
> > The little zippy guys aren't at risk of predation,
> 
> What about the little zippy dromaeosaurids? :-) And troodontids and...

Dromaeosaurs are set up to attack *bigger* stuff; troodontids seem to be
crepuscular and set up to go for *smaller* stuff.  There doesn't seem to
be a good wolf analog (taking deer about its own size); everything seem
to be either lions (ganging up on same size or larger animals) or foxes
(taking nothing much above half its own size.)

Also, dromaeosaurids don't seem to be faster than the small bipedal
herbivores; they're supposedly sprint-and-seize-and-slash types.

> > why are the smaller dinos so rare and the large ones so common?
> 
> Are they, apart from the usual explanations of preservational bias and
> the different probabilities to be overlooked in the field?

Dunno; the last stuff I saw on the subject come down pretty heavily on
'biazed toward large size', but I agree that it's a very difficult
question.

-- 
graydon@dsl.ca   |  Hige sceal þe heardra, heorte þe cenre,
                 |  mod sceal þe mare þe ure maegen lytlað.
                 |   -- Beorhtwold, "The Battle of Maldon"