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Re: Warm southern winters




"Tracy L. Ford" wrote:
> According to the present requirements of those families

You hit the nail on the head here. How can we be sure that plants living
100 million years ago had the same range of tolerance as their modern
counterparts?

> some of which are restricted to montane forests, tropical
> and subtropical, the climate was mild enough YEAR around, so that these
> ferns could reach an important ecological role in the community, which is
> reflected in the fossil record.

The plant fossils have always been a sticking point when it comes to
Mesozoic "polar" climate reconstructions. Every other type of evidence
points to cold conditions, yet the plant communities seem to contradict
this. To quote Rich, Vickers-Rich and Gangloff (2002):

"However, the diversity of the Late Early Cretaceous flora in south
eastern Australia and the large size of some of its trees exceed that
found in such cold environments TODAY [emphasis mine]. It is difficult
to imagine how this community functioned if the temperatures were as low
as the physical indicators suggest. No convincing explanation exists as
yet for this apparent anomaly."

Of course just because we can't imagine or explain how something came to
be, doesn't necessarily mean that it didn't happen. 

> Many of the taxa found in the strata belong to ferns

the dominant flora in southern Victoria during the EK

> which now live 

yes, which NOW LIVE

> in wet tropical to subtropical forests. Moreover, some of them
> could develop arborescent habit, therefore very cold conditions are
> UNTENABLE (me again) in the area during the early Aptian.

Based on the modern representitives of these families.

Straw-clutching aside, the plant fossils are perplexing in the way they
seem to contradict other lines of evidence. However the majority of
evidence points to cold conditions. Should we ignore all the other
physical lines of evidence just because there is one fly in the
theoretical ointment? Or should we, as I would suggest, do more research
to explain these discrepencies? Personally, I'm going with the weight of
evidence until something better comes alone. Plus, the idea of polar
dinosaurs is just too "cool" to let go of easily!  :)

-- 
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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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