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Re: Why Air Sacs?



On 11/17/06, Jerry D. Harris <jharris@dixie.edu> wrote:
However, the point of the paper isn't that bipedalism was impossible without
air sacs -- just that the evolution of air sacs _helps_ place a biped's
center of gravity in an optimal position to make bipedal locomotion more
efficient.

All ornithischians that was not fully quadrupedal, was facultative bipedal or there was fully bipedal ornithischians (the basal ornithischian that you mention bellow?)?

(They also propose that the evolution of the pubic boot had a
similar function in keeping the center of gravity as low to the ground as
possible -- it certainly couldn't hurt, but I don't think that _alone_ was
sufficient.)

Hmmm... A huge muscular tail was not more important to place the center of gravity well above the area between hindfeet?

existed to promote air sac evolution (I'm not a big fan of "THIS is the
reason why this feature evolved" types of arguments.)  (I also like
parentheses...could you tell?)

If we did not stick hard with evidences we'll end up with another "just so" history.

Presently, as odd as it seems, it seems most parsimonious
that air sacs evolved convergently at least twice, and perhaps three or four
times. Farmer does discuss this a bit in her paper -- she prefers the
quadruple convergence, but doesn't discuss other options.

I wonder about parabronchial lungs in that context.

[]s,

Roberto Takata