Re: mesosaurs, what are they?

[David Marjanovic <david.marjanovic@gmx.at>]

----- 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)".