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Re: dinosaur inspiration

On Tue, 24 Sep 1996, Tony Stout wrote:

> > On Tue, 17 Sep 1996, Rob Meyerson wrote:
> > 
> > > 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.
> Nick Longrich responds:
> > 
> >     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-....
> Forgive me if I'm reading this wrong, but doesn't Rob's statement refer to
> a generalized study of the TOP predators of the day, and not every predator
> within its own habitat?  

> If we were looking at the fossil record of today eons in the future, we
> probably would not assume Komodo dragons to be top predators, but simply
> 'forces to be reckoned with'.  While the dragons (and the other referenced
> creatures - Great Whites excepted) are certainly successful in their own
> particular niches, they are certainly not the TOP predators of the day, and
> would not be used in Rob's theory.  This would be left to animals like the
> big cats, wolves, and bears, which certainly can be used to deduce ideas
> about the metabolism of their prey.

        In Indonesia, monitors WERE the top predators, according to
Diamond. No lions, no tigers, no nothing. So I'm asking- since we know the
metabolism of our top predator in the ecosystem, if we discover the
dominant land herbivore, can we figure out what it's metabolism must have
been? According to this principle, dwarf elephants should therefore be
ectotherms, right? 
        And no pussy-footing around about "top predators" and
"continental". There's still the 20-30 ft. monitor lizards, snakes and
(?land) crocs of Australia. What are we to assume of a kangaroo they nab
for lunch? If that's not "continental" or "top predator" enough for you...
Pristichampsus also seems able to have made short work of at
least some of the Eocene's mammals. 

        I'm not saying there's no connection. This is making me realize
how much the metabolisms and mechanics of predator and prey are linked
(synapsid predator and prey finbacks, for ex?) and raises some interesting
questions about the origins of endothermy.
        But then again I'm thinking about therapsids (degree of endothermy
debated) vs. pareiasaurs. Pareiasaurs are turtle relatives- if we
discovered tomorrow that the top predators of the Permian, like the big
therapsids, were partially warm-blooded, who's going to jump out and say
"Aha! Scutosaurus is also partially endothermic!"? Or- hey, here's a fun
one  Hererrasaurus and the rhynchosaurs? If I tell you that Hererrasaurus
is a 100% mammal-style warm-blood, will you tell me the same must be true
of rhynchosaurs?

        And I'd still like to hear why dinosaurs CAN'T be modelled on
giant Pleistocene reptiles. Is it because dinosaurs are adapted for
extended bouts of aerobic activity? Or because dinosaurs extend to higher
latitudes than do these giants (confined, it would appear, to the
        -Nick L.