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Re: the start

 > Was dimetrodon a thecodont?

No, it was a Pelycosaur, which is a group of very early mammal-like
reptiles.  That it, it is more closely related to our own lineage
than to either dinosaurs or to modern lizards.

 > What separates thecodonts from Archosaurs,
 > besides hip structure?

Nothing, thecodonts are a *sub*group of Archosaurs.
Archosaurs include thecodonts and most or all of their descendents
(depending on if you are a cladist or not).  That is crocodiles,
pterosaurs, dinosaurs, and, to a cladist, birds are Archosaurs
as well.

Some also include a few other distantly related groups in
the Archosaurs.

 > Have thecodonts sometimes been called
 > "mammal-like reptiles"?

Nope, that is a seperate lineage - the one leading to true mammals.
They are so called because the later members of the group, the
Therapsids, are very much like mammals in many respects.

 >  If so, why?  I know "dont" refers to teeth,
 > what does "theco" refer to?

Groove.  It refers to the way the teeth are socketed in the jaw,
embedded in a groove.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.