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RE: Warm southern winters




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Dann Pigdon
Sent: Monday, July 22, 2002 2:05 PM
To: DML
Subject: Re: Warm southern winters


"Tracy L. Ford" wrote:


>>Okay. On the one hand we have unpublished hear-say by one person. On the
other, we have several published papers by experts in geology and
permafrost conditions. Until the alternative theory is published, and
peer-reviewed, I'm going with the odds.<<

Understandible and probably correct.

>> [Iceberg/glacial dropstones]

> Whats the published papers on this? I'd be interested to read them.

I'll have to look this up. I believe it was mentioned in "Wildlife of
Gondwana". I'll get back to you with any specific references.<<

Ok, but this is one of the things my, ah..., other person was referring to.



> Ok, but are all alpine forest's have a snow period? I haven't a clue if
they
> have to have one or not.

The prevailing theory about the Koonwarra fish beds is that the
creatures died when a shallow section of the lake froze over, either
freezing the animals to death or, more likely, cutting off their oxygen
supply.<<

What about an algae, or some other thing cutting off the oxygen supply?

>

> See http://www.alphalink.com.au/~dannj/ecenvir.htm<<
>
> Nice link. So can all those plants you listed live in a climate that
freezes
> over? Do any of them do that today?

As you yourself pointed out, we shouldn't impose our modern predjudices
onto Mesozoic ecosystems. The on-going pollen and wood analysis of Doris
Seegers Villiers indicates that although the numbers of pollen and
spores found in the Strzelecki siltstones and mudstones are high, the
diversity of species is low. Perhaps this indicates a rather specialised
floral ecosystem. Also, ferns and other low-growing plants (like club
mosses) appear to have dominated. We know that trees grew in the area
(petrified trunks, fossilised leaves), however they may not have formed
a continuous forest canopy.<<

Ferns are dominate? Why not a temperate climate? Why ignore the plants?

> Fine, let me 'try' again. What about the Antarctic Cretaceous dinosaurs?
> Hadrosaurs and ankylosaurs? Where they covered in integument to survive
the
> supposed frosty winters? No way IMHO. What about the Freamouv Formation?
> Would that have had a 'frosty' time? Procolophonids, labyrinthodontis,
> prolacertaforms..

Australia was some-what of a peninsular, and cut up into smaller islands
at times during the EK. The rest of Antarctica seems to have been more
intact, perhaps allowing large animals (like hadrosaurs) to migrate
seasonally (as has been suggested for the Arctic dinosaur faunae).
Ankylosaur scutes are also found in Victoria, so perhaps these animals
could cope with the colder conditions (perhaps with fat reserves, since
they were already adapted to carrying a heavy load).<<

Hey, is there a map showing the Cretaceous land masses for Australia like
they have for the Late Cretaceous inland sea? That'd be great to see.

>> [Plesiosaur breeding practices]
>
> Well, this is a theory. Pretty good one...So, what's the paper/s on this?
> Just so I'm up to date on this.

There was a paper recently referenced here on the list, about an
Antarctic sub-adult plesiosaur.

Fostowicz-Frelik, ?. and GaYdzicki, A. 2001. Anatomy and histology of
plesiosaur bones from the Late Cretaceous of Seymour Island, Antarctic
Peninsula. In: A. GaYdzicki (ed.), Palaeontological Results of the
Polish
Antarctic Expeditions. Part III. _Palaeontologia Polonica_ 60: 7-32.

I don't know if anything seminal has been published on the South
Australian opalised marine reptiles, but you can read about them at the
S.A.Museum's website:

http://www.samuseum.sa.gov.au/plesiosaur/screen.htm

> >>Hypsilophodontids may have also chosen the polar areas to breed in.<<
>
> Don't know that for sure. Have there been any eggs/eggshells found yet?

No, but they have found embryonic hypsie bones at Flat Rocks (115 MYA).
So they definitely bred their. The remains of baby hypsies have also
been found in the opal fields of South Australia. See:

http://www.cmnh.org/dinoarch/2002Feb/msg00687.html<<

Another problem is the actual collection area is small and the eggs or nest
may be buried someplace they haven't or can't get to...



> 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?<<

I suppose they have. Ask a botanist or paleobotanist.


> 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.


> 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<<

Right, living groups (or species?) so if they know where and in what climate
they live NOW, they it should be the same back then.

> 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!  :)<<

Personally I'd go with the plants. These can be tested today. If the other
physical evidence is geologic, then there may be another interpretation than
the one that is currently thought. We know more about what's living today
than we do in the past.

--

>>...mentioned in a previous post. Parts of Antarctica were further from
the pole than the furthest reaches of Australia. Plus, if there were
less ocean bodies around Antarctica, then different ocean currents may
have caused localised difference in climate (as would geographic
features like mountain ranges, etc).<<

and if the world was warmer than it is today then a cold poles would be out
of the norm.


Tracy L. Ford
P. O. Box 1171
Poway Ca  92074