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Re: Dinosaur Beaks



Kris Kripchak (MariusRomanus@aol.com) wrote:

<The basal bird *Confuciusornis* not only had a beak, but it also seemed
to have had a truly deep beak because of the bony struts on the face. Even
the back of the head in the postorbital region of this bird was thicker
than most birds of the time. It is not too surprising that a bird that
shows signs of such massive reinforcements of its skull would also have
had a great thickness to its rhamphotheca.>

  Most birds that have a "weakly" reinforced skull show a large beak
structure, as well. The premaxilla/maxilla unit in birds is usually a
massive structure, with weak struts around it that support only the
kinetic system or, as in some few birds such as *Gastornis*,
dromornithids, and parrots, a reinforcing beam system in the lachrymal and
jugal that relate to stresses imposed during bite through the rostrum. The
tendency of living birds with such a beak (parrots, some finches) to crack
things with these beaks imply how these beaks with elongate and deep
symphyses and large rostra in gastornithids and dromornithids used THEIR
beaks. This same set up in a primitive bird prior to unrecoverable loss of
the lateral and temporal bones of the skull or fusion of these to one
another simply reinforces, as in *Jeholornis*, that the jaw was used for
cracking. This has nothing to do with the presence of a keratinized beak.

<Point in fact.... What you are doing here is very similar to the argument
 that was given saying that since *Archaeopteryx* had feathers and 
*Compsognathus* did not, it was shown to be evidence that the ceolurosaur
had naked skin. (Sad thing is, some still believe this.)>

  Contrary to this, I think my position is different. Absence of
preservation of integument apart from scales and features would imply
nothing had skin, but this is not true. No lizard preserves the full
sheath of scales in any lagerstätten, largely because there are no
ossicles in the scales that enforce preservation. The sheathing of the
scales does not permit them to be preserved around the body, even as
impressions, and rarely as an outline. Does this mean they were
naked-skinned? My point is that preservation qualities hardly give us a
clue, but it does advance some  ideas, and the absence of a scalation in
some cases does not mean they weren't there, but hard preservation, such
as bones, occurs rarely for scales.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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