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Re: Dino Feathers

At 12:05 AM 8/2/95, GSP1954@aol.com wrote:
>Some of the bird-like theropods s
>uch as Archaeopteryx, dromaeosaurs, troodonts, oviraptors, therizinosaurs,
>etc have a folding arm system that approaches but does not match the avian
>condition. Why? I suspect it is because they descended from early fliers, but
>that remains speculative.

Greg et al -

        Yes, I know you made the rather controversial statement in your
book, and I've seen the unpublished form of the paper you and Ken wrote on
the "secondarily flightless  descendants of the archaeopterygians"
hypothesis for the rest of the Maniraptora.  Since I'm not a functional
morphologist, I can't really comment, but I have studied a bit the
"collapseable" nature of the arms in some of the Mesozoic birds, which, as
you say, is somewhat more advanced than that of the theropods (due, of
course, to function in flight).

        But...do the specific characteristics that make the theropod arm
foldable _only_ serve in that capacity?  That is to say, do those same
traits also serve to make the arm more dextrous overall, in extension as
well as contraction?  Given that so many have attributed such
"maniraptoran" grasping/clutching etc. abilities to these theropods, I
don't wonder if the traits evolved separately for this group.  Obviously,
until we find better basal maniraptoran fossils (and, BTW, Gordon Bell has
informed me that one of SDSM's digs near Sundance, WY has uncovered a
disarticulated but otherwise good specimen of what he says may be a new
species of _Ornitholestes_) the question is entirely debatable either

Jerry D. Harris
Schuler Museum of Paleontology
Southern Methodist University
        (Compuserve:  73132,3372)

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