[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Sifaka and Chukar Behavior: Trees Down or Ground Up?
Jaime A. Headden" <firstname.lastname@example.org> wrote:
Sifakas lack any leg-gliding equipment, leaping aided almost wholly by a
"halo" of body hair including some extra long underarm hair badly in need
of trimming, inducing greater drag than in sleeker animals or other
Feduccia went one step further, and suggested that the "brachial mat" (the
long matted hair along the trailing edge of the arm) of the sifaka may
constitute an airfoil.
So we now have two possible hypotheses for avian flight orgin, ground up
supported by Ken Dial's experiments with galliforms, and trees down
supported by Xu et al. on new (and not so new) fossils from the middle
Cretaceous of Liaoning.
As others on this list have said, I'm not certain that one can claim that
the two hypotheses are mutually exclusive. WAIR gets the creature up the
tree, and the four wings gets it back down to the ground - in one piece.
WAIR also provides a functional explanation for the development of the wing
stroke - or at least the co-option (exaptation) of the predatory stroke for
a locomotory purpose. The matter of which came first in theropod evolution
- the rudimentary flight stroke or the predatory stroke - depends on what
phylogeny you favour.
An ambush predator cannot afford to maximize predatory equipment into a
locomotory structure; [snip] animals that glide cannot simply switch to
predatory mode while in flight, meaning that the wing structures are
independant of predation.
I agree and disagree at the same time. I agree that use of the arms in
aerial locomotion is irreconcilable with concomitant use of the arms in prey
seizure. But, what if the forelimbs had become detached from
grasping+holding predation by virtue of those lethal eumaniraptoran feet?
The new MSN 8: advanced junk mail protection and 2 months FREE*