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Thero palms (was Re: bird evolution)

At 12:05 AM 3/19/99 -0800, Tracy Ford wrote:
>T. Mike Keesey wrote:
>> Many theropod illustration show the hands in an incorrect, palms-down
>> position. In reality, the palms probably faced inward more, like those of
>> birds.
>Not all theropods held their hands palms facing each other. Allosaurs,
>didn't and I dont' think Ornithimimds did eather. I have a list
>somewhere listing which ones did. 

Actually, allosaurs probably did (new specimens with articulated carpus of
_Allosaurus_ and _Acrocanthosaurus_ show this better), as did ornithomimids
(ditto for ornithomimid specimens at BHI).

>Greg could give a better list (He did say something about it a few years
>(?) ago on the list. I should be in the archives, but I don't know
>where). I'm sure Thom, could also.

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).

Galton and Sereno both have papers on theropod (or more generally,
saurischian) hand orientation coming out in the near future (DinoFest volume
at least, maybe elsewhere too).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661