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Re: the start




On Tue, 7 Jun 1994, MICHAEL ERNST wrote:

>  U > Gary, dinosaurs belong to a group of reptiles called Archosaurs which
>  U > evolved
>  U > from reptiles called thecodonts during the middle/late Triassic.
>  U > Archosaurs include all Dinosaurs, pterosaurs (winged reptiles), birds,
>  U > and
>  U > Crocodilians.  Thecondonts evolved from early Diapsid reptiles.
> 
> Was dimetrodon a thecodont?  What separates thecodonts from Archosaurs,
> besides hip structure?  Have thecodonts sometimes been called
> "mammal-like reptiles"?  If so, why?  I know "dont" refers to teeth,
> what does "theco" refer to?
> 
> ---
>  * OFFLINE 1.54 * michael.ernst@tigerteam.org
> ..............................................................................
> 
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---
Dimetrodon was not a thecodont, it belonged to a group of reptiles called
Pelycosaurs which are synapsids (one hole in the skull) where as
thecodonts are diapsid (two holes in the skull).
Thecodonts ("theco" = socketed , "dont" = tooth)
Thecodonts have never been considered mammal-like reptiles however some
fossil mammal-like reptiles have been mistakenly placed in the Thecodonts
because of poor or undiagnostic remains.
---
John Schneiderman
dino@cwis.unomaha.edu