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RE: SICB Report, part 1 (long)



I may be asking for it here, but; would a short tail in a dinosaur indicate
more of an "avian leaning" (pun semi intended)?  I'm thinking of the
Therizinosaurus
here.

Cheers;
Dwight

        -----Original Message-----
        From:   Pharris Nicholas J [SMTP:pharrinj@plu.edu]
        Sent:   Thursday, January 14, 1999 5:50 PM
        To:     Betty Cunningham
        Cc:     luisrey@ndirect.co.uk; th81@umail.umd.edu; dinosaur@usc.edu
        Subject:        Re: SICB Report, part 1 (long)



        On Thu, 14 Jan 1999, Betty Cunningham wrote:

        > Birds don't stick out behind at all but MANY still stick out in
        > front-including the early forms we DO know.
        > What balances birds in this? the upright S-shaped posture of the
neck
        > over the shoulder and keel

        > -Betty Cunningham

        One thing I haven't seen mentioned in this thread yet is that modern
        birds, unlike non-avian theropods, have (nearly) immobile femora
that, as
        far as I can tell, stick straight forward, effectively displacing
the
        "hip" joint (actually the knee) to a position under the wings.

        My suspicion would be that at the same time as aerodynamic
considerations
        forced the shortening of the tail in the line leading to modern
birds,
        balance was maintained through the locking of the femora in a
forward
        position (effectively sacrificing a leg segment in return for an
        aerodynamically suitable tail), along with  some reorganization of
the
        posture, as Betty suggested.
         
        Nick Pharris
        Pacific Lutheran University
        Tacoma, WA 98447
        (253)535-7045