Re: New Velociraptorine

[Jeff Poling <jpoling@dinosauria.com>]

At 03:10 PM 12/12/96 -0500, Mickey Rowe wrote:

>[ The opposite of "retractor" is "extensor", and I think you've got
>  that backwards from what Russ is proposing.  -- MR ]

   That would be correct.  Ligament to extend, muscle to retract.  This
takes care of the "unexercised extensor muscle" issue that someone
brought up.

[ Sorry to break in again, but my reading of Russ' analogy made
  more sense the opposite way.  To quote him: "I think you should
  expect to see the claw pulled back much as necks get pulled back."
  What pulls the neck back is the nuchal ligament.  The reason such a
  ligament is useful is that it maintains force with a much lower
  energy requirement than an equivalently sized muscle.  The drawback
  (no pun intended) is that work must be done against this ligament in
  order to move in the opposite direction (a ligament can't relax like
  an opposing muscle could).  What you're suggesting above is that the
  animal's default position was "claw extended", or instead that the
  animal constantly expended energy against the ligament in order to
  keep the claw retracted.  I don't know about everyone else, but that
  doesn't seem like a sensible design to me.  Also aside from it
  seeming to be backwards from Russ' neck analogy, it's not clear to
  me that Russ was even thinking about ligaments when he brought up
  the subject...  I'll step aside now and let Russ argue it if he so
  chooses.  -- MR P.S. Russ was also the "someone" that brought up the
  subject of unexercised extensors. ]

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