Re: Eagle eyes/ORNITHISCHIAN EYES

["King, Norm R" <NKing@usi.edu>]

Pete Buchholz wrote (3/22/00; 9:17pm):

>I suggest that the reason ornithischians got palpabrals in the first place
is 
so that the eyes wouldn't fall out of their heads-; or more exactly, so that

the eyeballs and eyelids would have ample attachment areas within the eye 
socket because the frontals were so thin and narrow side-to-side.<


But Chris Brochu said palpebrals are best developed in robust, blunt-snouted
crocodylians.

As he pointed out, they are apparently not homologous with dinosaurian
palpebrals.  Apparently their functions were entirely different?  

As for another suggestion, I wonder how strong the selection pressure would
be for shading one's eyes against a bright sun?  

Perhaps palpebrals are linked to some other character that is/was more
strongly selected for.  These suggestions seem almost like "just so" stories
(recalling some discussions on this list from a few years ago).

There seem  to be two separate questions here:

1.  What good are palpebrals?

2.  Why did palpebrals arise?