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the supracoracoideus system and bird flight



Richard Cowen's e-mail address has sort of changed, so listproc didn't
recognize him.  It will recognize you next time Richard.  In the mean
time, this is a message Richard submitted to the list:
  
  Date: Tue, 31 Oct 1995 10:02:40 PST
  From: cowen@geology.ucdavis.edu
  To: dinosaur@lepomis.psych.upenn.edu
  Message-Id: <00998B00.7A9A9710.8@geology.ucdavis.edu>
  Subject: Ostrom in Colorado

  Kata McCarville quoted John Ostrom as saying that birds can still
  fly if you sever the tendon that operates the leverage of the
  supracoracoideus system.  This experiment was done in the 1930s in
  Nazi Germany (Sy et al.). They took pigeons, severed the tendon, and
  then encouraged them to fly by unspecified methods. They could not
  take off. So they opened the window and threw them out. Hey presto,
  flight! That is, the pigeons could maintain airspeed once they had
  acquired it by being thrown out of the window.  So the bare fact is
  true, but it has no relevance to the flight of A., in my
  opinion. We're back to the situation of a bird without a
  supracoracoideus.  It can only take off if it jumps from a
  height. What is worse, and what is not addressed in most discussions
  of the supracoracoideus, is that birds slow down by rapid, repeated
  wing flapping (as well as spreading tails, feet, etc.). A bird
  without a supracoracoideus system will have difficulty landing under
  control, especially on the ground - not being able to shed velocity
  by swooping up to a branch. Yes, I know that some tropical seabirds
  simply fly right into the beach and fall on their faces, but it's
  not something I'd recommend.  In summary, I still maintain that if
  Archaeopteryx could fly at all, it was a lousy flier. It had
  precisely the worst possible kind of tail for flight (Spearman) -
  the worst shape, with feathers mounted on a long bony tail. It did
  not have the supracoracoideus that other flying birds need for good
  take-off and safe landing. It did not have the box-like pelvis that
  makes a sound undercarriage - again for the shock of landing. It did
  not have the long primary feathers at the ends of the wing that are
  needed for best lift: instead, it retained the vicious little claws
  of its theropod ancestors.  It did not have the flexible wishbone
  that helps to give the repeated rhythmic wingbeat in today's flying
  birds: instead, its furcula is thick and rigid.  One in seven
  specimens has a very thin sternum, which if anything argues for the
  kind of pre-flight flapping that Lipps and I associate with display,
  and Padian associates with powerful predatory strikes - rather than
  full flight.  And we (or at least I) still don't have a very clear
  picture of the morphology of the sternum on specimen 7.
  
  I KNOW I'm biased, but the display hypothesis provides a sound
  integrated explanation of all the features of Archaeopteryx, and a
  sound background for the origin of flight IN LATER BIRDS. There are
  problems with all the other hypotheses. At least, Lipps and I
  deserve a fair shake for our hypothesis.  Given that, I am confident
  that science will take its course, and am happy to allow new finds
  (of Archaeopteryx or any other early bird) to permit further
  testing.
  
  OK, I'll try to keep quiet for a while now
  
  Richard Cowen