Re: Scales, hair, integumentary structure relationships?

[Michael Habib <mhabib5@jhmi.edu>]

> > A few years back they found a mutant chicken with teeth in its beak -
>
> Really? Can you give us a source for that?

I don't know about just finding them, but chicks can be stimulated to 
produce teeth in the jaw without too much trouble, if the correct 
protein triggers are provided.  The basic genetic background is 
apparently still in place.

> > Some birds (hoatzin, african touraco, the ostrich?) seem to have 
> > re-evolved claws, using the genes already present in their genome
>
> No, most extant birds have small claws on one or two fingers per wing. 
> Check out the next chicken or turkey on your table!

Well, I'd still say he's correct on the hoatzin: the juvenile state in 
that taxon clearly has fingers that are more separated, and more 
strongly clawed (not to mention consistently clawed) than the usual 
condition we see in crown group birds.  Of course, this is partly 
turning on gene switches, and partially related to delay of 
developmental timing.

I'm also a bit intrigued by your qualification of "most" - when I did 
some quick reference searches on clawed modern birds, a few groups came 
up regularly (swifts, for example), but it's hardly the "norm" in most 
groups.  It would seem to be a reasonably common, yet fairly 
stochastic, effect.  Do you have a more recent citation that 
demonstrates otherwise?

Cheers,

--Mike


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu