Re: New Feathered Dinosaur

["Tim Williams" <twilliams_alpha@hotmail.com>]

Patrick Mellor wrote:


> Looking at croc ancestors, and early crocs, their skeletal proportions 
> >often seem to be very cursorial, and they seem to have had fully >upright 
> posture. These are classic signs of endothermy, but modern >crocs are fully 
> ectothermic.


If the bipedal crocodylomorphs of the Triassic period (usually referred to 
as sphenosuchians) represent a monophyletic group, then it is likely that 
upright posture and bipedality are derived characters within the 
Crocodylomorpha, evolved within the sphenosuchian lineage.  Under this 
scenario, the Crocodylia (including modern crocodilians) retained the 
quadrupedal posture that is primitive for the Archosauriformes (and the 
Crocodylomorpha).


Tim


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

Timothy J. Williams

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

Phone: 515 294 9233
Fax:   515 294 3163

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