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thoughts on Dinocephalosaurus (long)



Dear all
Both Dan Varner and Jeff Hecht called our attention on publications about Dinocephalosaurus in Science and in other journals .
I wish to share my thoughts about this animal and about what has been written on it and, obviously I will be happy of any eventual reply.
1) it's amazing how similar are the vertebrate faunas of our (Switzerland+Italy) Middle Triassic Western Tethys and the Eastern Tethys. Even odd critters like Tanystropheus have something similar over there. To me these affinities represent an important paleocological indicator.
2) In the paper on Science, the age is reported as 230 million years ago and Anisian.
I may be wrong, but according to the latest edition of the International Stratigraphic Chart , the Anisian should end at 237 (+ - 2) million years ago, thus either the level isn't 230 myr ago or it should be Ladinian.
3) In the article quoted by Dan Varner, it is written that protorosaurs lie in the the ancestry of dinosaurs. Surely they are closer than synapsids, but, it seems to me that there is some agreement that they could be the sister group of archosaurs as a whole, thus this claim of ancestry is a bit excessive, perhaps without the word dinosaur no one will pay attention to anything? mah...
4) In the article quoted by Jeff Hecht there is a comparison with Tanystropheus neck and, if I read correctly, it is written that the neck of Tanystropheus is about half the length of that of Dinocephalosaurus. Nope. Big specimens of Tanystropheus have a neck as long as or even longer than that of Dinocephalosaurus both as absolute size and also proportionally. It is true that the number of cervical vertebrae in Tanystropheus is roughly one half that of Dinocephalosaurus, but each vertebra is much longer, as correctly pointed out in the original paper in Science.
5) The limbs of Dinocephalosaurus are more paddle like than those of Tanystropheus, and carpal and especially tarsal bones look like those of most nothosaurs: simple rounded bones; In comparison, the tarsus of Tanystropheus, with its tightly packed bones is much more terrestrial-like. As authors noticed in the paper in Science, despite the similarity Dinocephalosaurus is not strictly related to Tanystropheus, but it seems an offshot from a more basal stock of protorosaurs and the elongate neck was acquired independently. Perhaps the long neck served different purposes in the two taxa which may have lived in (slightly?) different environments.
Thanks to all who read my blabberings until here. But anyway, where else one should exchange ideas, right?


                                                         Silvio Renesto


_

" Men take in great consideration what falls within their sphere of knowledge, but they don't realize how much it depends from what is beyond that""
(Zhuang Zhi)



Prof. Silvio Renesto
Department of Structural and Functional Biology
Università degli Studi dell Insubria
via Dunant 3
21100 Varese
Italy
phone +39-0332-421560
e-mail: silvio.renesto@uninsubria.it
see my Triassic website at http://dipbsf.uninsubria.it/paleo/