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Dwarf Allosaurs (was Re: Archeoraptor Article)



Sara Burch wrote:
> 
> It said _Tyrannosaurus_ may have had down on it's body when it was a
> baby, which it shed out as it got older,

This has got me thinking. Could the prevalence of dwarf allosaurs  (between 4
and 6 metres ) in southern Australia have something to do with the polar
climate? The remains of at least three "allosaurids" are known, from the Early
Cretaceous of Victoria and Western Australia, and the Late Cretaceous of Western
Australia.

The typical mammalian response to cold climates is to evolve larger body sizes
to conserve heat. However in polar Australia you have dwarf "allosaurs". Could
this perhaps have something to do with theropods loosing feathers after
attaining a particular size, therefore these polar theropods retained juvenile
characteristics (such as small size and a feathery coating) into adulthood? To
quote L.A.Frakes 1997 "Grossplots: a Method for Estimating the Temperature State
of the Earth and of Australia, Cretaceous to Middle Miocene" Aust. J. Bot.,
1997, 45, 359?372:

"(1) during the Early Cretaceous, the south-east of the continent was subjected
to freezing wintertime temperatures; (2) peak warming of northern Australia was
attained in the Turonian?Santonian, but this was followed by cooling later in
the Cretaceous;

I'm not sure exactly when in the Late Cretaceous the allosaur-like remains from
WA are dated to. If they're after the Turonian-Santonian then perhaps my theory
holds up. Otherwise, just forget this entire post.  :)
 
-- 
____________________________________________________
        Dann Pigdon
        GIS Archaeologist
        Melbourne, Australia

        Australian Dinosaurs:
        http://www.geocities.com/capecanaveral/4459/
        http://www.alphalink.com.au/~dannj
____________________________________________________