Re: snout to beak

["Scott Hartman" <scott_hartman@hotmail.com>]

Caleb Lewis asked:

> > .   I was wondering, if dinos did evolve into birds, how did the 
> > transition from the dinosaurs' snouts to bird beaks occur?<<<

    Well, of course beaks aren't primitive for vertebrates, so no matter 
who you hypothesize birds evolved from, the transitionhad to occur 
somewhere.  However, many, if not most theropods have horned ridges and/or 
hornlets on their snouts, that were probably covered with keratin.  Greg 
Paul has suggested that the long paired ridges in dromsaeosaurs may have 
united to form a proto-beak.  Even if not true for dromsaeosaurs, something 
of this sort must have happened at some point.  However, it certainly isn't 
obvious that the earliest toothed birds, like Archaeopteryx, had beaks, so 
the real question may be how _bird_ snouts evolved into bird beaks.
    Finally, beaks are apparently pretty easy structures to evolve, they 
appear independantly in multiple groups of dinosaurs, synapsids, etc.

Scott
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