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RE: feathered ornithopods?




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Dann Pigdon
Sent: Saturday, July 20, 2002 2:15 PM
To: DML
Subject: Re: feathered ornithopods?


"
>>There are labyrinthodont remains dating to 120 MYA, but no crocs. Things
warm up a tad by about 115 MYA - you find croc remains, but no more
labyrinthodonts. This suggests that crocs outcompeted the labys, the
prevailing theory for the rest of the world as well, and that labys
survived in this area to the Early Cretaceous because crocs were kept
out, probably by cold temperatures.<<
But, as per Vickers-Rich, P., 1996, p. 723...The evidence is suggestive, but
not definitive, however, for there is one other possible explanation that
cannot be ruled out. Temnospondyl fossils are known from the Strzelecki
Group only in the high energy sediments that represent fanglomerates pouring
off the margins of the rift valley. This coarse facies occurs widely in the
western exposures of the Aptian Strzelecki Group, but is less common in the
younger Aptian Otway Group. Perhaps temnospondyls were facies controlled,
and thus their absence is owing to sparsity of the coarse fanglomerate
facies in the younger sediments of the Otway Group, rather than thie
rextinction by the Albian owing to temperature increase or some other
factor...
Hmmm, stronger rivers favor temnospondyls rather than crocodilians? (Or is
it the other way around?)
Vickers-Rich, P., 1996, Early Cretaceous Polar tetrapods from the Great
Southern Rift valley, Southeastern Australia: In: Proceedings of the
Gondwana Dinosaur Symposium, Memoirs of the Queensland Museum, v. 39, part
3, p. 719-723.
Same volume, Wiffen on New Zealand, p. 730. The climate of New Zealand at
that time seems to have been temperate, judging from the dinosaurian and
plant fossils. Some plant material suggest that leaves were dropped during
the winter forming leaf mats although conifers, not these deciduous forms,
still apper to have dominated the forest in this region. The recovered
dinosaur material shows no special adaptations to cold climates...
How can New Zealand be temperate while Australia frosty?
Wiffen, J., 1996, Dinosaurian Palaeobiology: A New Zealand perspective:
Proceedings of the Gondwana Dinosaur Symposium, Memoirs of the Queensland
Museum, v. 39, part 3, p. 725-731.

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