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Re: Why did the metatarsals of birds fuse together?

-----Original Message-----
From: Henri R&#1046;nkk&#1046; <overmind@iobox.fi>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Thursday, November 16, 2000 6:26 AM
Subject: Why did the metatarsals of birds fuse together?

>Dear all,
>Why did the metatarsals of birds fuse together? Some time ago, some one
(I'm sorry, I don't remember the name) posted onto this list that the fusion
was an adaptation to hopping from branch to branch. I think I didn't get the
logit. Would it be that the fusion made the tarso-metatarsus part of the
limb stronger, and so less vulnerable to facture during rapid deceleration
occuring when the bird "lands" on a branch.

Henri...I believe I once stated that the "advanced mesotarsal ankle"
developed in the theropod ankle (assuming a BCF origin for theropods) as an
adaptation for leaping free of the branches just prior to flight as a way to
get good initial momentum. Both the simple hinge and the extended leverage
allowed by the fused tarsometatarsus would be a refinement of this ability.
If anything though, the fusion of the metatarsals to each other would reduce
the "shock absorption" ability of having to land on stiff branches. It may
have been the ability to control a soft landing by rapid wingbeat
(development of sternum and furcula) that "lessened the need for" the shock
absorptive capacity of unfused metatarsals....just a thought (other opinions
may vary..8^).