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Re: Scales, hair, integumentary structure relationships?



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