RE: Permian protofeathers???

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Ken Kinman wrote:

>But what makes such discussions even more difficult is the controversy
>over whether Eoraptor and 
>herrerasaurids are cladistically "true" dinosaurs, 

The differing interpretations - i.e whether _Eoraptor_ and the
herrerasaurids were immediately basal to the Saurischia-Ornithischia, or
whether they were basal saurischians or basal theropods - hinges on the
polarity of a very small set of characters.  (And what holds for _Eoraptor_
may not be true for herrersaurids.)  Under any of these scenarios, the
overall phylogenetic position of _Eoraptor_ and the herrerasaurids is not
altered profoundly - in contrast to (for example) the phylogenetic
somersaults that the segnosaurs (therizinosaurs) have been subjected to over
the past fifteen years.

Irrespective of the precise position of _Eoraptor_, this taxon is widely
regarded as morphologically closest to what the first dinosaur would have
looked like.

 
> I believe the oldest dinosaur is now the one in southern Brazil
>which was something like 237 million years old, and it was over six feet
>long.

I believe there are dinosaur specimens from Madagascar that are older still;
but I'll have to check.


Tim

------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163