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RE: Pachyrhinosaur nasal horn? (was RE: OMEISAUR CLUBS, PACHYRHINOSAUR)




-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Williams, Tim
Sent: Friday, May 24, 2002 9:30 AM
To: 'dinosaur@usc.edu'
Subject: RE: Pachyrhinosaur nasal horn? (was RE: OMEISAUR CLUBS,
PACHYRHINOSAUR)

Tracy Ford wrote:

> The keratin on the beak of birds and their feathers are formed
> differently. Don't fall into the trap of them being both keratin they
> are exactly the same.

Not 'exactly the same' at all, I agree.  But if birds can build hard
supracranial structures out of epidermal tissue, I can't see why dinosaurs
couldn't.  For example, the casque of adult cassowaries is constructed of a
bony base or core underneath a keratinous structure.  However, the keratin
casque may *double* the height of the underlying bone, and the keratinous
structure does not necessarily conform to the shape of the bone buried
inside it.<<

But it is using the bone as a template.

>>No doubt the pachyostatic boss of pachyrhinosaurs was sheathed in horn.<<

No doubt at all, your are correct.

>>What this debate boils down to is what shape this horny layer took: did it
faithfully conform to the shape of the underlying bone (mostly blunt and
rounded at the top), or was it extended dorsally into a more apical, conical
structure (mimicking the bony horn cores of other ceratopsids).  Or
something between these two extremes.<<

IMHO it was more rounded and boss shaped and not extended like a horn.

>>David asked why a keratinous horn would be an advantage over a bony horn.
I
can think of one possible explanation: pain.  A keratinous horn is less
painful when broken. <<

Or when hit. Now, I find it interesting that the frill of Triceratops (the
bone texture, groves etc) look exactly the same as the oribital horns. Was
there a horny sheath on the frill also? Or no horny sheath over the horns?




Tim



------------------------------------------------------------


Timothy J. Williams, Ph.D.

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074