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



 
Mike Taylor wrote:

> > No horn, no horn, NO HORN. It was a BOSS! Why can't people except
> > this? They had a boss, that's it! Leave the horn off!
>
> Well, that about wraps it up, then.  Got _me_ convinced, anyhow.

Yeah, me too.  I guess the debate is over then.


Tracy Ford wrote:

> I've had this discussion with people for over 10 YEARS now. The 
> comments are always the same, they don't change. 

And your answer evey time is...? 

> A rhinoceros's horn is keratin, but it's hair, dinosaurs don't have 
> hair. 

I know.  So what?  I was using the rhino as an analog - I by no means
implied that a nasal horn of a pachyrhinosaur was made of hair.  Keratin is
the major component of nails and feathers, as well as hair.  

> Dinosaurs have a keratinous horn that covers and followings the 
> existing skeletal structure. 

Since keratin does not usually preserve in fossils, I'm not sure why you can
be so confident of this.  If dinosaurs did build novel epidermal structures
out of keratin, we would not normally expect to find them.

There's no need for keratinized structures in dinosaurs to 'cover or follow'
existing structures.  What about feathers?  What about the 'quills' of that
porcupine-tailed psittacosaur?  There's no fundamental reason why a
ceratopsian couldn't build a horn out of keratin.  Similarly, the swellings
and domes seen on the skull roofs of certain abelisaurs (and _Labocania_?)
may have served as the bases for cornified horns.



Tim



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



Timothy J. Williams, Ph.D. 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 9359