Re: Gliders to Fliers? (Was Re: Ruben Strikes Back)

["James R. Cunningham" <jrccea@bellsouth.net>]

Casey wrote:

> Archaeopteryx falls closely in between the two groupings
> suggesting a partial arboreal/terrestrial lifestyle.

I believe the suggestion is that of an indeterminate lifestyle rather than
evidence of a partial arboreal/terrestrial lifestyle.

>  This would agree
> with a trees-down hypothesis for the evolution of flight from a small
> theropod.

Archaeopteryx appears to be too highly derived to address that question.  I
speculate that Archie's legs were strong enough to enable takeoff from the
ground by leaping, in a manner somewhat similar to a quail,  without running
as a requirement (but I haven't done the force curves required to quantify
the leaping launch -- I have roughly quantified a running launch -- Archie
does quite well, and can get off at a much lower speed than Berger suggests,
without the need to be a really good runner).  Min power flight speed wasn't
very high, and it didn't take much energy to reach it. I speculate that
Archie may have used his tail to carry the weight of his legs at low speed,
but would have unloaded the tail and carried the leg weight with the wings
during cruise, to take advantage of the increased efficiency of the unloaded
tail.

> Regardless of the
> reason, Gatesy's data suggests a partial arboreal/terrestrial lifestyle.

I'm not sure that it suggests that, though it is not inconsistent with
it.Jim