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Re: Polar dinosaurs



Tracy Ford wrote:
> 
> * Ok, the book says that sauropods are rare at the Ridge consiting of teeth.
> They have some opalized caudal centra from Sheepyard, 80 km west of Lighting
> ridge. I take it this means further inland. I don't think that would
> miminize the cold or the long nights just because it's more inland. Wasn't
> all of Australia subject to long nights?

Lightning Ridge may have been cold, but if the deposits are Early
Cretaceous (which I think they are) then this is well north of the
"polar" regions (that is, within the equivalent of the Antarctic
circle). Also, climate tends to vary with time. As I mentioned, crocs
are absent from Victoria 115 MYA, but present 106 MYA, suggesting a
slight warming of the climate, at least enough to extend the range of
crocs further south to commence the "Great Labyrinthodont Feast". The
range of any particular animal may have varied every few million years
(or even in the order to tens of thousands of years). Since we don't
generally have that sort of resolution in Mesozoic deposits, it can be
hard to tell whether sauropods ranged as far south as Lightning Ridge
all of the time, or only during warmer periods of climatic oscillation.

I would think the greatest barrier to sauropod distribution would be
their offspring. Whales could live in polar waters all year round if
they wanted to, but have to migrate to warmer waters in order to breed.
Once they reach a certain size they are fairly indifferent to the cold. 


> Tibia found in Coocoran. I don't know how far that is from the coast.

Can it be determined what season the deposits were layed down? Koonwarra
was almost certainly formed at the onset of winter, with freezing
conditions killing animals quickly. Plus there is at least one flower
present (115-118 MYA), suggesting it was not yet fully winter. The
presence of bird feathers in what seem to be relatively good condition
suggests that birds may have still been around at that time of year. As
to whether they stayed all winter, or got out when the going got really
tough (and dark), is difficult to say.

> Muttaburrasaurus would have
> had to cross some major stretches of open ocean to get from Victoria to
> Queensland during the Early Cretaceous.<<

>> Right so they had to be living there all the time (or at least in
>> Australia).

In the north of the continent, yes. I don't think there is any evidence
of Muttuburrasaurs in Victoria (although Atlascopcosaurus may be a
smaller relative - perhaps a "Muttuburrasaurid" adapted to the more
extreme conditions?)

-- 
____________________________________________
        Dann Pigdon
        GIS Archaeologist
        Melbourne, Australia

        Australian Dinosaurs:
        http://home.alphalink.com.au/~dannj
        http://www.geocities.com/dannj.geo
____________________________________________