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Re: Avian flight stroke origin

Demetrios Vital <demetrios.vital@gmail.com> wrote:

> Osteologically speaking, does a juvenile hoatzin show a greater capability 
> for grasping than most maniraptorans?

In _Dinosaurs of the Air_, GSP certainly argues that the juvenile
hoatzin serves as the best modern analog for how _Archaeopteryx_ might
have climbed trees, with the hands and feet both used to "clamber
about branches quadrupedally".

However, it must be remembered that the pes of the hoatzin is superbly
adapted for anisodactyl grasping, with a hallux that is large,
reversed, and fully descended.  The hoatzin is, after all, an arboreal
bird.  Additionally, hoatzin chicks have extremely large legs and feet
in proportion to their body size.

There is a nice illustration of a juvenile hoatzin clambering over a
branch in Bakker's _The Dinosaur Heresies_ (p.315).  It underscores
just how important the big, grasping feet are for climbing.
Comparisons between small Mesozoic maniraptorans and modern hoatzin
chicks focus on the use of wing-claws in clambering, but often
overlook the important role of the perching feet of hoatzins.