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Re: dinosaur inspiration



At 11:07 AM 9/25/96 -0500, Nick Longrich writes:
 
>       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. 

Touche' on this one.  As I have mentioned privately, no researcher
worth their salt would stop with the assumption that the top predators
and the top herbivores had the same metabolism, but would seek to
prove the true metabolism in other, more diagnostic, ways.  All that
this idea would do is set up a few paramaters for study.

As one last jab at a comatose horse, let me point out that the
Australian Dingo is a formidable predator, and may be better suited
for the "top predator" position than the crocodile (especially out in
the dryer climates of the continent).  Let me also add that when the
metabolisms of the predators are considerably less than those of the
herbivores, the predators need to develop some unique strategy so they
can eat (i.e. ambush predation).  However, for the predators and
herbivores that are relatively close evolutionary cousins (how's that
for a string of adjectives) we could safely assume that they have
similar metabolisms (like classing mammals together as endotherms).

>       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?

No, because the species in question are not closely related, and
therefore not applicable to my hypothesis.

>       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
>tropics)?

Probably both.  We could also add Horner's evidence for high growth
rates in the Maiasauria, as well as half-a-dozen other lines of
reasoning.

Rob Meyerson
Orphan Vertebrate Paleontologist

***
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