The retroverted hallux of birds

["Henri Rönkkö" <overmind@iobox.fi>]

 Dear all,

I'm interested in the detailed structure of the fully retroverted hallux of 
birds having it.

How is it attached to the rest of the limb? Halluxes in usual animals sprout 
from more proximal limb, it seems to me. But the avian retroverted hallux 
sprouts from the same level as other toes.

I once read, from Sereno's paper on Sinornis, I think, that metatarsal I is 
attached to metatarsal II, near the distal end of the latter. This sounds quite 
strange to me!

I tried to find out more by looking at extant bird skeletons, but it appears 
the metatarsals have fused into one solid mess. I could only see that a bulge 
protruded from the distal area of the tarso-metatarsus, to which the 
retroverted hallux attached.

So, if you can tell me more about the hallux, I'd appreciate it.

Thanks in advance,
Henri Rönkkö
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