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Re: Deinonychus claw use and origin of flapping
Denver Fowler <email@example.com> wrote:
> 3. The ability to do something is not the same as selecting for it.
> I agree that little theropods may have been able to climb trees, but the
> ability to perform an action is not the same as having a
> selectable pathway by which morphology can be changed.
Agreed, 100%. For small paravians, it all hinges on whether certain
changes at the extremities were related to climbing or not.
> I remain skeptical about arboreal / scansorial adaptations or habits in these
> small theropods, especially regarding the
> subarctometatarsalian metatarsus of the basal deinonychosaurians. This is a
> cursorial adaptation, so why it would be selected for
> in an arboreal animal is currently unexplained.
(1) If a small theropod divided its time between the land and the
trees, it might still retain or acquire cursorial abilities for the
terrestrial part of a "dual-mode" ecology. This would be especially
true of a small paravian that spent most of its time on the ground,
and only occasionally ventured up or into trees.
(2) It's my understanding that the "wedge-and-buttress"
arctometatarsalian condition (and the less derived
subarctometatarsalian condition) is tied to the transmission of forces
up and down the distal hindlimb during foot-fall. It offered
advantages to highly cursorial animals (Holtz, 1994). But I wonder if
it might also be advantageous to animals descending to the ground from
height (such as leaping or gliding out of trees), to help cushion the
impact of landing. I just came up with this notion off the top off my
head, and I'd be more than happy to be wrong here.