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Re: Phylogeny of Maniraptora




James R. Cunningham <jrccea@bellsouth.net> wrote:

And doesn't this imply that passive gliding is easier to achieve than active flapping? Is that indeed the case?

I think it's fair to say that active flapping is far more aerodynamically and biomechanically challenging than passive gliding. To my knowledge, only four lineages in the history of the earth have achieved sustained flight: insects, pterosaurs, birds and bats. (Five if you include humans, beginning with the Wright brothers... but that's beside the point.)


Gliding, by contrast, has evolved many, many times. The marsupials and rodents alone have each produced four lineages of aerial gliders.

> But as I've noted in previous posts, the firmer attachment of the remiges to
> the manus has _nothing_ to do with the mechanics of powered flight.


I missed those posts. Why not?

The increased width of the middle (feather-bearing) finger allowed for a firmer attachment of the primaries. This presumably assisted in flight, but the firmer attachment per se is not explicitly associated with the mechanics of powered flight.


Why does not being the primordial function mean that it had nothing to do with the mechanics of powered flight?

I didn't mean to imply that. What I was ruminating about was that the broader phalanx of the middle finger may not have evolved to be an aid in powered flight. There is an argument put forward that dromaeosaurids that have this feature are secondarily flightless. Sure, this character was employed at some stage in powered flight; but I reject the assertion that this must have been its original purpose. I was raising alternatives.


Using my right hand to control the stick for roll and pitch control isn't its primordial function

As far as we know, the first primates never flew planes, so your example is probably a correct one. But if we ever find a fossilized lemur preserved in the remains of a wooden biplane, I'm going to take this point up again, Jim!!!!


;-)



Tim

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