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dromaeosaurs and birds



Jonathan Wagner wrote: ". . . if one wants to assume that dromaeosaurs
started out this way, one then has to explain how they moved into the
'running predator' niche".

Only a small creature would be able to leap up onto low-lying vegetation
without crushing it or breaking the branches; perhaps the larger 'running
predator' style dromaeosaur predecessors never exploited the
off-the-ground niches.

to continue my thoughts about the origin of flight:

Features of the "pouncing on ground-level prey from above" scenario
that I like are; 1) a bipedal creature could do it; 2) the forelimbs would be
used initially for balance (as we do when we jump from a low height)
and later could be exapted for control during the fall; 3) the creatures
would not be spending all of their time in the trees and would therefore
tend not evolve  the "four grasping limbs" design of most arboreal
animals; 4) one could envision a gradual evolution of both control and
lifting capabilities, with each intermediate stage adaptive and useful; 5)
birds do this sort of thing all the time (owls catching mice from above,
eagles swooping down on rabbits) and we are not forced to invent a
type of predation (leaping after flying insects) that does not exist today;
6) the hindlimbs could move gradually from a running foot to a foot
designed to grasp both branches and prey, driven by the likelihood that
the prey would be grasped by whatever limbs were closest to the
ground as the creature descended toward the prey, namely the
hindlimbs (since the forelimbs would be involved in balance and control);
and 7) small theropods seem to be the most likely to have had feathered
insulation, and the feathers could have been easily adapted to assume
both the control and lift functions.

The more I think about this, the better I like it.

James

James M. Norton, Ph.D.
University of New England
11 Hill's Beach Road
Biddeford, ME  04005
phone: [207]283-0171 x2270
fax: [207]283-3249
email: jnorton@mailbox.une.edu