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Re: mesosaurs, what are they?



----- Original Message -----
From: "david peters" <davidrpeters@earthlink.net>
To: <dinosaur@usc.edu>
Sent: Friday, February 04, 2005 11:37 PM
Subject: mesosaurs, what are they?

What are mesosaurs?
[...]
Why can't mesosaurs be a basal sauropterygians, perhaps close to Lariosaurus?

I'll not pretend to understand the recent research on Paleozoic sauropsid phylogeny. I can only say that sauropterygians always come out as crown-group diapsids (though whether they're lepidosauromorphs or archosauromorphs...), while mesosaurs are something completely different. They have now found a home at the base of... erm... Anapsida = Pantestudines; in other words, they are very basal sauropsids. See here http://tolweb.org/tree?group=Amniota&contgroup=Terrestrial_Vertebrates where "the position of Mesosauridae follows Modesto (1999)".