Re: Scales, hair, integumentary structure relationships?

[David Marjanovic <david.marjanovic@gmx.at>]

> Actually, it's the second and third *metacarpal* (the bones of the
> palm of the hand) that fuse.  In all modern birds, including hoatzins
> (correct me if I'm wrong), the actual phalanges of the third digit are
> very small and encased in the flesh of the manus.

In all* modern birds, including the hoatzin at all growth stages, the third 
finger contains a single short bone which is probably a fusion product and 
encased in the same flesh as the second finger. The second and third 
metacarpals are fused at the proximal and the distal end; the first 
metacarpal is very short and fused to the proximal ends of the others as 
well as to the distal carpals.

I was asked yesterday to provide a source that says most birds have claws on 
the first and/or second fingers. I have come across a few places, such as 
Feduccia's 1996 book, which cite a "Fischer 1942" paper which is said to 
report finger claws from all "orders" except six. Granted, the claws (and 
the bones that carry them) are usually very small and straight.

* Ostriches are reported to sometimes have a claw on the third finger in 
addition to those of the first two. That probably means a second bone in the 
third finger. On the other hand, some (!) kiwis lack the third finger 
entirely, and moas lack wings entirely, but I think this covers all 
exceptions.