RE: Prosauropods & Edmarka

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

Rob Gay wrote:

> I can't vouch for Eoraptor and Herrerasaurus, but in both Dilophosaurus,
> and Coelophysis, the radius is locked in place with the ulna near the 
> elbow, preventing medial twisting.

Yep, you're right.  The configuration of the radius+ulna prevented any
pronation/supination of the forearm.  I should have clarified what I meant.
The 'cobblestone'-like carpal arrangement in basal theropods and ceratosaurs
allowed a large degree of axial torsion at the wrist.  In tetanurines,
however, there is a tendency to consolidate and combine the carpal elements
into structures that functioned as a unit (i.e. carpal blocks - though the
homology of the 'blocks' in allosaurids and maniraptorans is disputed).  The
swivel-like maniraptoran carpus barred any extensive torsion at the wrist.

So maniraptorans couldn't dribble a basketball.



Tim


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

Timothy J. Williams, Ph.D.

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

Phone: 515 294 9233
Fax:   515 294 9359