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Re: Crylophosaurus and Australia



Phil Hore wrote:

> Look at Australia compared to Africa. Africa has several carnivores that fill 
> each niche. Large carnivores you have lions, leopards, hyenas etc. Medium 
> sized carnivores you have cheetahs, jackals etc and so on? (this is only a 
> rough guide) but in Australia you only seem to have one animal in each roll. 
> Large-thylacoleo, medium thylacine, small quolls-devils.

Many of these Australian carnivores are only known from fossils. Since
not every species fossilises (or is known from fossils), then can we 
really compare living carnivore assemblages to fossil ones? Plus you 
left out  the reptiles (crocs, varanids, snakes), some of which would 
have qualified as 'large' carnivores.

You are also comparing an island continent to one attached to Europe and
ultimately Asia. Australia the Gondwanan peninsular may (perhaps
'would') have been different to Australia the island. Large carnivore
species could easily have migrated in and out of Africa, thus
contributing to carnivore diversity. I have no doubt this was true of
Australia the Gondwanan peninsular.

> Certainly we have never had the interspecies mingling that other continents 
> have had, and in no way am I trying to compare modern Australia to 
> prehistoric Australia (environment etc). I?m just trying to point out that 
> some environments do indeed do exactly that - they do produce vast, continent 
> filling numbers of animals from a very small original stock.

Then we are largely in agreement? Except that modern (or geologically
recent) Australian environments can not really be compared to Gondwanan
environments.

> Now let me ask you, is it not more then likely that two fossils, found in 
> locations that would have been reasonably close at the time (though separated 
> by a gulf in time), that seem to be similar (with what little is known for 
> the oz polar allosaur) are more likely to be somehow related than not?

How are Cryolophosaurus and the allosauroid astragalus similar? I wasn't
aware that an astragalus was known for Cryo. 

Besides, look at it statistically. Cryo is (as far as I'm aware) the
only large theropod known from Antarctica. Was it the only large
theropod species that ever lived there? I doubt it. Was the theropod
represented by an allosauroid astragalus the only large theropod that
lived in Gondwanan Australia? Again, this is doubtful, given that during
Gondwanan times (and before) it was possible for theropods to move in
and out of the Australian peninsular from India, South Africa, etc.

So we have two fossils, separated by both space and time, with no
overlapping skeletal elements, which are almost certainly not
representitive of the entire large theropod biota in either place/time.
The likelyhood of these two being directly related is extremely remote.
The possibility is always there; it simply requires proof (for which
there is none at the time).

-- 
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Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
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