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Re: Scales, hair, integumentary structure relationships?



Quoting Erik Boehm <erikboehm07@yahoo.com>:

"That would just be two characters out of several hundred (assuming today's
methods of phylogenetics). It would hardly matter."

You're assuming a well preserved specimen, fragmentary remains and a little luck preserving the primitive looking features could result in a specimen appearing quite anachronistic

Yeah, but the rest of (say) a chicken skeleton looks a heckuva lot more like other modern birds than an early toothed bird. I suppose if only the "throwback" features were preserved, then yes, you would have a point, but that seems spectacularly unlikely. And, as Mike mentioned, chickens with teeth are not known to just happen, though chicken embryos can be biochemically induced to grow teeth.



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.

Well, by claws, I meant it in a more broad term, more than just the what tips the finger.
Most birds fuse all three fingers, right? the ancestral condition of maniraptors was not fused. The ancestral condition of the neoornithes has the fingers fused right? so those birds showing unfused fingers are showing an atavism?

No, modern birds fuse the second and third fingers together, but the "thumb" remains independently mobile and controls the alula, a kind of leading-edge flap on the bird's wing.


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.

Note, moreover, that in all birds the second and third metacarpal start off unfused and fuse over the course of development. Viewed in that way, fused vs. unfused boils down to a question of developmental timing.