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Re: dinosaur inspiration

On Wed, 18 Sep 1996, Rob Meyerson wrote:

> At 04:39 PM 9/17/96 -0500, Nick Longrich writes [quoting Rob -- MR]:
> >> I concentrate on the theropods for one reason, if we can determine the
> >> metabolism of the predators, we can safely assume a similar metabolism
> >> for the herbivores.
> >
> >     Komodo dragons, pit vipers and crocodiles (both modern and the 
> >Eocene Pristichampsus) come to mind as exceptions, along with the Great 
> >White and bird-eating spiders- for that matter, presumably any spiders 
> >would have metabolisms quite different from partially-endothermic 
> >flying insects they capture. Granted, these are all generally (maybe with 
> >the exception of the Great White) ambush, rather than pursuit, predators, 
> >but there are also endothermic ambush predators (many cats).
> However, none of these animals are in the position of
> Top-Land-Carnivore.  It is this species which will determine the
> minimum endothermic level of the Top-Land-Herbivore.  Lower down on
> the food chain, things might get a little less certain, even getting
> to the point where the rule might not apply, but it can be extremely
> useful for the largest land animals.  I can't quite make this fit for
> crocodiles though, perhaps there is something special about their
> niche which allows them to dominate in areas with a high mammal
> population.

        At least in Indonesia, Komodos seem to have been in exactly
that position and, believe it or not it would appear that they hunted
pygmy mammoths (and any other oxymorons hapless enough to cross their
paths- well, okay, there I take a few liberties).  That would seem to
put them at the level of "top predator". God only knows what else
could describe a monstrosity like Megalania (...actually, somebody
mentioned a while back it was sunk into the existing genus of large
monitors) which got as large as one tonne and perhaps as large as
three (that's a guestimate)- unless the thing was a scavenger (a
terrestrial scavenger, as Greg Paul notes, does not seem to be a
viable way to make a living). For more info on the Komodos see an
article by Jared Diamond in Discover a couple years back.
        And as for Pristichampsus, its teeth were supposed to have been 
mistaken for T. rex teeth- so judge for yourself what that would imply 
about the niche it lived in. 
        Granted, crocs have a bit more temperature regulation than other 
reptiles, and monitors have the fastest metabolisms of any lizards. But as 
for "top land herbivore", how about Collossochelys/Geochelone, a truly 
gargantuan tortoise from Recent India which, if I remember correctly, 
was a tonne or more? And it had to deal with tigers. I'm not saying that 
these are unconnected, just that we can't deduce automatically one from 
the other. 
        Now, wouldn't it be interesting to have a look at those things 
and see how long your giant monitors and giant turtles take to reach one 
tonne compared to your average dinosaur?