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In a message dated 8/21/01 9:16:22 AM EST, luisrey@ndirect.co.uk writes:

<< So yes, I apologize for the inclusion of Mesenosaurus as part of the bird
 lineage. That is obviously the Past. That illustration is from 1994 OMNI
 magazine BCF article. For an update (and what George Olshevsky also propose
 now: instead of Mesenosaurus a prolacertilian) see the new 'BCF' article in 
 new Dinopress Vol 4. and the next one Vol 5. >>

Right, I agree with the current assessment that Mesenosaurus is not a 
diapsid. Ivakhnenko & Kurzanov were pretty convincing, however, and besides, 
Mesenosaurus as they redescribed it fit quite well with my idea of an 
ancestral archosaur. After reading Dave Peters' recent paper on pterosaur 
origins and prolacertiforms, I think prolacertiforms come the closest to 
being archosaur ancestors within Diapsida. Not to mention [1] several 
prolacertiforms show antorbital fenestrae, which was (once) an archosaur 
autapomorphy, and [2] prolacertiforms include Cosesaurus, Longisquama, and 
Megalancosaurus in various places in their cladogram, all of which I once 
included in Archosauria as basalmost archosaurs or dinosaurs. Dave's paper 
gives us a much better handle on the relationships of these reptiles and 
indirectly explains why pterosaurs were considered archosaurs for so long.