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Re: To climb or not to climb
Patric Norton wrote:
>Date: 16 Dec 1998 13:25:45 -0500
>From: "Norton, Patrick" <Patrick.Norton@state.me.us>
>To: "dinosaur list (comment line)" <email@example.com>
>Subject: Re: To climb or not to climb
>An interesting thought. I've often wondered what may have triggered the
>fusion of bones seen in the carpometacarpus, particularly since birds
>were flying well before that occurred. Release from selective pressures
>for a grasping hand might do it......but there's a long time between the
>first probable flyer and the first evidence of a carpometacarpus. My
>thought was that the grasping hand was related to predation, and that the
>evolution of the reversed hallux (grasping foot) freed the arms entirely
>for flight by allowing the foot to take over the prey capture function.
>But I'm sure I'm the one out on a limb on this one.
I`ve always assumed that the evolution of flight in birds went hand in hand
with the evolution of gymnosperm and later angiosperm trees. Not only was
the grasping foot with reversed hallux an aid in perching on narrow
branches, but the further development of the wing and flight musculature
resulted in the maneuverability necessary to negotiate the intertwining
branches. This may also have been a reason for the apparent decline of
smaller pterosaur species in the Cretaceous, a loss of habitat. I can see
pterosaurs landing on long springy Cycad type leaves, but not upon
angiosperm branches (I think they lacked that precise maneuverability). They
may have been confined to relatively tropical areas that sported cycads,
until outcompeted even on their own turf by the evolving avian form.
Just me going out on a limb with more of my "speculation".