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Re: Flight



>With regard to arboreal adaptation - Alan Feduccia recently published a
>study of the claws of Archaeopteryx and birds, and suggested that
>Archaeopteryx's claws were more similar to those of arboreal birds than to
>cursorial birds, but there are problems with his analysis.  First, he was
>using the hand claws of Archaeopteryx - something no living adult bird has.
>Second, he didn't include any nonavian dinosaurs in his analysis.  Thomas
>Holtz presented a paper at the recent SVP meeting and showed that the claws
>of Archaeopteryx are very similar to those of nonavian theropods.

Indeed, the best matches for Archie claws are in many case (no big
surprise) to be found in "maniraptoran" theropods.  One comment on
Feduccia's study: he refers to the manual claws of Archaeopteryx as being
laterally compressed, unlike any theropod or other predator.  However, a)
we can't say for certain that these claws are laterally compressed, since
no one has prepared one of them out and b) laterally compressed manual
claws are a character found in almost all advanced coelurosaurs, the group
from which Archaeopteryx was derived (or more properly, the group in which
it belongs).  Furthermore, felids (cats) are characterized by laterally
compressed claws as well, although they are more highly curved than
Archaeopteryx or most dromaeosaurids.

One thing I did point out while being husseled off stage was that
arboreality and terrestrial predation are not mutually exclusive behaviors.
Small felids are arboreal (or more properly, scansorial [= climbers])
animals which do most of their hunting on the ground.  I would suggest that
Archie was an animal which may have indeed spent some time in trees or
bushes, but which preyed on lizards, sphenodontids, amphibians, and maybe
some early mammals, insects, and pterosaurs, on the ground.  Some of the
adaptations for arboreality/scansoriality (in particular, curved claws)
also work very well for siezing and dismembering prey, and laterally
compressed claws are especially predatory features (allowing for blade-like
slashes in the prey).

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.