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Dino wrists (was Re: Thero palms...)





>"Thomas R. Holtz, Jr." wrote:
>
>> Sereno argues that all theropods from herrerasaurids on up walked 
with palms
>> inward.  However, having seen palm prints for probable coelophysoid 
tracks,
>> I suspect that the palms-inward orientation has to do more with the
>> development of the semilunate carpal block, a structure now known to 
be an
>> avetheropod, and possibly tetanurine, feature.  (Note that an 
*enlarged*
>> semilunate carpal block, as seen in troodontids, oviraptorosaurs,
>> _Caudipteryx_, _Protarchaeopteryx_, dromaeosaurids, and birds, still 
seems
>> to be synapomorphic for Maniraptora).

<snip>

>Regarding the diagnosis of _Compsognathus_, I am sure that some of this
>disagreement derives from the disarticulated nature of the carpal and 
manual
>elements of the _Compsognathus_ specimens, and the fact that some of 
these bones
>are missing altogether.  Following the discovery of the well-preserved
>_Sinosauropteryx_ specimens (four specimens in all, the last I heard), 
the
>wrists and hands of compsognathids should be easier to assess.  The 
"Theropoda"
>article, written by Philip J. Currie, which is also in _The 
Encyclopedia of
>Dinosaurs_, includes the following passage on page 733:
>
>"(MANIRAPTORA) has been redefined by Holtz (1996) to include only all 
theropods
>closer to birds than to ornithomimids.  He went on to establish the 
taxon
>Maniraptoriformes, defined as the most recent common ancestor of 
_Ornithomimus_
>and birds and all descendants of that common ancestor (Fig. 2).
>Maniraptoriformes are characterized by a pulley-like wrist joint that 
allowed
>the hand to be pulled back against the body.  This characteristic was
>secondarily reduced or lost in ornithomimids and tyrannosaurids.  
Recently
>discovered compsognathids (see FEATHERED DINOSAURS) have well-preserved 
hands
>that suggest that this character was more widespread among 
coelurosaurs."
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My question is this: is there some general consensus as to the range of 
wrist articulation in various theropod groups?  That is, what kind of 
wrist mobility is suggested for a T. rex? or an allosaurid? or a 
compsognathid?

Thanks in advance!

-Kevin

"Thank goodness for opposable thumbs!"
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