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Re: mammalian reptiles

Chris Nedin's post is much appreciated; it's nice to see how many  
"fact police" there are in this group. I just wanted to make a quick  
comment about one thing before I collapse from exhaustion (not the  
fault of the post!). The "euryapsid" group is no longer recognized as   
a "natural" (monophyletic) group by anyone who studies fossil  
vertebrates (apparently the following paper argues otherwise: Mazin,  
J.-M.  1982.  Affinites et phylogenie des Ichthyopterygia. Geobios,  
Memoire Speciale 6:85-98). All of the critters in that group are  
derived from WITHIN the diapsids - most of the reptiles one can think  
of are diapsids, except the turtles (god's gift to the planet Earth,  
as far as I'm concerned) and the "mammal-like reptiles," which are a  
paraphyletic stem-group for mammals, of course. The traditional  
"euryapsids" include two major groups: the ichthyosaurs and the  
sauropterygians. According to Rieppel (1994: J Vert Paleo 14:9-23)  
the sauropterygia includes plesiosaurs, the nothosaurs, the  
placodonts, and another primitive group called the pachypleurosaurs.  
I'm not familiar with the pachypleurosaurs; everyone has seen  
paintings and pictures of plesiosaurs and nothosaurs; and the  
placodonts are really bizarre and deserve being looked up if you can  
find an illustration. Everyone seems to agree that nothosaurs are  
closely related to plesiosaurs, and perhaps a paraphyletic stem-group  
leading up to them, although Rieppel argues that the nothosaurs are  
monophyletic. Apparently there is no strong evidence linking the  
sauropterygians and ichthyosaurs, and hence, "Eurapsida" isn't really  
a useful term. Night all...