Eagle eyes

[dbensen <dbensen@gotnet.net>]

I was studying some skeletal reconstructions of ornithopods today and I noticed
something that I had never thought much of before.  Many (I won't say all, for
there may be exceptions) ornithopods have a nob of bone extending over their
eyes.  This palpebral bone, as it is called, would give  them a fobidding "eagal
eye" (that forbidding glare common to raptors) in life (I remember reading
something to the effect in a Gregory Paul essay).  My question is this: "Why 
would
you evolve a palpebral bone?"  Obviously, it is something good, for both raptors
and ornithopods had them, and since predatory dinosaurs didn't have them, must
have evolved the structure independantly (right?)

So, what is their function?

Thanks
Dan