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Ahmed al-Mahasa Sha'ad wrote:
<<If this happend in origin of birds it does NOT mean
it MUST happen in every linage of tree-living
Rob Gay wrote:
<So the question is, what drove this to happen in
birds and not in the other tree-dwelling predators?
What sort of circumstances, that are not present
today, would make therapod dinosaurs fly?>
Hypothesis: Development of flight in theropod
dinosaurs, leading to birds, was derived from a
arboreal habit of leaping down upon prey, developing
modified limbs and structures to control descent.
Test: What leaping animals take prey this way, and
what are the characteristics of such behaviors? How
can this be applied to the trees-down model of
Jaguars of South America ambush prey from above
(capybaras, tapirs); they do so and have been known to
do so from about 15-20 ft above their targets.
Details: jaguars weight roughly 200lbs., and are close
to 4ft in length, excluding tail, though I may be
over- and underestimating, respectively; distance
relative to length and mass is not considerable to
harm the predator without it having some sort of
problem or injury, but then it wouldn't be up in a
tree to ambush a tapir. Comparison: *Archaeopteryx* is
a lot smaller than a jaguar. Though studies show
Archie wasn't a really good flyer (as in Yalden,
Wellnhofer, Ostrom refs.) it is not inconsiderable
that it did this from atree and gliding onto prey, it
was from a much smaller distance relative to size than
is shown in ambushing gliding snakes (one of the
reasons they do this?, from footage -- Discovery
Channel, and yeah, I know...), and this may not have
been a primary factor in the behavior of Archie.
Liaoning exhibits fauna much more suitable to testing,
but these creatures are full-fledged birds
(*Changchengornis,* *Liaoningornis,* *Chaoyangia,*
*Confuciusornis*), having anatomy consistent with
powered flight (Chiappe, 1995; Zhou et al., 1995;
Chiappe et al., 1999) and so may not be suitable to
Problem: Jaguars, and all other carnivorans, in
fact, lack "gliding" structures altogether, in spite
of a long fossil history of forms built to ambush in
this manner. Suggested conclusion: While not
selective, leaping onto prey from above as a driving
factor to develop "gliding" and then "flight"
structures does not seem to fit a provided model in
comparison to an extant example.
Further tests: Why do snakes glide, do sugar gliders
and flying squirrels, or flying frogs make use of the
gliding mode to attain prey, or selective position
from which to aquire prey? All known forms acheiving a
gliding structure except rodentians are carnivores....
Jaime "James" A. Headden
Dinosaurs are horrible, terrible creatures! Even the
fluffy ones, the snuggle-up-at-night-with ones. You think
they're fun and sweet, but watch out for that stray tail
spike! Down, gaston, down, boy! No, not on top of Momma!
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