Re: Bird arms

["Jaime A. Headden" <qilongia@yahoo.com>]

Rachel Clark, the Raptor Gal, wrote:

<All this talk about secondarily flightless dinosaurs has got me
wondering...  How come, when flying dinosaurs decide to return to the
ground, they usually reduce the arms, in some cases making them mere
vestiges or practically nonexistent?  Wouldn't it make more sense to
evolve "normal" arms again, since you're not using them for flight
anymore?  Boy, evolution is full of weird quirks...>

  Hmmm. *Caudipteryx* has unusual manual claw morphology, with a blunt
thumb claw, very hook-like second finger claw, and a third finger claw
with a blunt end on a hook-like curved, but much more slender
dorsoventrally than the other two claws, and preservation assures me
the claws are not smashed too far to bely this analysis.

  *Protarchaeopteryx* claws all remain very hooked, and the arm
structure is very similar to dromaeosaur and oviraptorosaur
morphoplogy (understandably) as is *Caudipteryx'*.

  Care to speculate with me on the use of *Mononykus*, *Shuvuuia*,
*Protarchaeopteryx*, and *Caudipteryx* claw uses as compared to each
other?

  Flight may have been displaced to make effective use of these claws,
and thus developing the arms to use the claws in such a way. Even with
short arms, *Caudipteryx* could still, it seems, reach the head,
thigh, and all points between, so the arms were not totally made
useless in respect to length. Probably like ostrich arms, which are
still very useful. Hmmm. Even like phorusrhacoid (or *Titanis*) claws.

  Jaime A. Headden
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