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RE: Ah ha! That's where therizinosaurs came from



Tim Williams wrote-

> Somebody (in this case me) will point to the fused carpometacarpus in
> the oviraptorosaurs _Avimimus_ and _Heyuannia_, and in the
> deinonychosaur _Balaur_. In these cases, fusion of the
> carpometacarpus might very well be associated with lack of use.

I don't know what the function of a carpometacarpus is, but I doubt it's 
correlated with a "lack of use".  In addition to the above taxa and the 
previously noted alvarezsauroids, Therizinosaurus, Oviraptor and Mapusaurus 
also show fusion among flightless taxa.  Therizinosaurus, Oviraptor and Balaur 
have large well developed hands, and while those of Heyuannia and Avimimus 
(Tsuihiji et al., 2009) are more robust and slender respectively, neither shows 
obvious reduction in utility.  The fusion in Mapusaurus shows that unless you 
subscribe to BCF, the feature can arise in nonvolant theropods at least 
sometimes.  That said, the other taxa may be neoflightless, especially Balaur 
if Cau is right about it being an avialan.

Mickey Mortimer