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Re: Ah ha! That's where therizinosaurs came from



On 8/15/2011 11:43 AM, Mike Keesey wrote:
On Sun, Aug 14, 2011 at 9:42 PM, Tim Williams<tijawi@gmail.com>  wrote:
>  The biggest problem with GSP's "neoflightless" hypothesis is this:  It
>  proposes that tree-dwelling theropods had plenty of time to evolve an
>  extensive list of "flight-related" characters (advanced
>  scapula-coracoid morphology; foldable forelimbs; shorter and distally
>  stiffened tails; large contour feathers on the limbs and tail; etc).
>  But over this same time, these tree-dwelling theropods didn't get
>  around to evolving any arboreal characters.  I find this perplexing.

That's only a problem if you assume that "trees-down" is an essential
part of the neoflightless hypothesis. It doesn't seem to me that it
is. The neoflightless hypothesis may still be valid if avialans
(apomorphy-based sense) developed flight from the ground up.

It is also possible that cursorial ground foragers roosted nightly in easily climbable trees (such as cycads) -- this lifestyle could utilize both passive and active paths to powered flight simultaneously.