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Re: Giant flightless birds

At 10:05 AM 11/05/1999 -0400, you wrote:
>.. Archaeopteryx had three
>free digits (even pterosaurs had three free digits), but they don`t seem to
>be opposable. Still, they were functional for "hooking" onto branches and
>clambering about in the treetops. Hoatzin chicks have two, which function in
>similar manner. Now, T_Rex also has two. Again, I can see this as a holdover
>from a previous "hoatzin-like" state.

Except that the hoatzin has not lost any digits.  It still has the same
number - three - as almost any other modern bird, but only two have
functional claws (in the chick).  This is not comparable to T. rex which
actually lost digits.

The only birds I know of to have actually lost digits on the hand are
secondarily flightless species in which digit loss is part of an overall
reduction in the wing elements (eg kiwis, with a single digit, and moas,
which had apparently lost their wings altogether).

Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@home.com