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ORNITHOMIMOSAUR ARMS AGAIN



Some weeks back Greg brought to attention what 
implications the _Sinornithomimus_ specimens might have 
for forelimb mobility in ornithomimosaurs. Because the 
figured specimen seems to have a pronated manus in which 
all articulations appear true, the implication was that 
ornithomimosaurs (and maybe other theropods) really could 
pronate the manus after all. 

In describing the forelimb skeleton of _Struthiomimus 
altus_, Nicholls & Russell (1985) said the following of the 
ulna...

'The concave articular facet for receipt of the radius is deep 
and well developed. The form of both the proximal and 
distal radioulnar articulations is suggestive of the presence 
of syndesmotic unions in life. Such joints, binding the 
elements by way of collagenous fibres, would permit slight 
play between the elements but limit rotatory ability' (p. 649)

Ken Carpenter recently described the same system in other 
theropods. If Greg is right about _Sinornithomimus_ I 
wonder then if theropods were more variable than we've 
thought. Maybe most (including _S. altus_) couldn't pronate 
but a few could. I'm doing this without Kobayashi et al. to 
hand so cannot check the figures. Thoughts appreciated.

-- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

email: darren.naish@port.ac.uk
tel: 023 92846045