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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