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Re: Palms in

How is the presence (or absence) of a semilunate carpal block related to the extent to which a theropod could or could not pronate its palms in this manner? Is that action solely limited to the morphology of the radius and ulna? I'm curious because the speculation earlier on the list that the "palms in" orientation may be limited to the tetanurines is consistent with other observations that the presence of a semilunate carpal block is limited to that clade.<<<

A salient point; the semilunate carpal caps parts of both the ulna and the radius, so at least a well developed semilunate _would_ preclude pronation. In Allosaurus, however, the semilunate is poorly developed, and would not be difficult to free up. Yet there is little additional movement imparted, since the ulna and radius can't move along their long axis'. So the reduction of mobility still must be what is being selected for.


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