Phoenix Skeptics in the Pub Message Board › In re: Book Discussion on 2012-08-24 (Krauss & Dawkins)
Even though I was unable to read THE BLIND WATCHMAKER, I mentioned Archaeopteryx as an example of a dinosaur with feathers and articulated digits:
See the phylogeny section, specfically:
There are clearly articulated digits in the forelimbs.
Compare the bone structure of the forelimbs to modern birds:
"The carpus and metacarpus form the "wrist" and "hand" of the bird, and the digits (fingers) are fused together."
I cite this as evidence of simplification of structure over time. Evolution doesn't necessarily produce complexity. It can, but will not always operate in this direction.
Talk Origins (great site, by the way) uses the bones as evidence for macro evolution:
and shows the side-by-side comparisons of the evolution of the wing from pre-Archaeopteryx to modern chickens.
"As one follows the line from ancestor through descendants, the functions and forms can come and go, but the underlying structures must grade from one into another, relatively unchanged."
The key here is that functions (what the animal does with the structure of their body) may not always be required and may change, but they can't change their structure. As certain actions become no longer necessary, evolution can produce changes that impact the animal that produces only a slight disadvantage and therefore isn't enough to remove the attribute all together.
In the case of fusing, it's likely more advantageous to not maintain the extra muscle, cartlidge, and tendons to support that extra degree of freedom of movement. Thus, fusing is advantageous due to a conservation of energy of development and maintenance.
Long post. I don't blame you if tl;dr.