Re: Horning in

[zone65@bigpond.com]

On Friday, February 27, 2004, at 01:22  AM, David Marjanovic wrote:

> From: David Marjanovic <david.marjanovic@gmx.at>
> Date: Fri Feb 27, 2004  1:22:10  AM Australia/Canberra
> To: DML <dinosaur@usc.edu>
> Subject: Re: Horning in
> Reply-To: david.marjanovic@gmx.at
>
> > > Like the horns of many (if not all) extant animals, their horn cores 
> > > were
> > covered by a keratin sheath. Extant reptiles with horns show this, I
> believe
> > the evidence comes from growth marks on the core.
>
> In addition, all bone that isn't covered by skin is covered by 
> keratin. The
> only exceptions are deer antlers (which are _dead_ bone) and placoderm 
> jaws
> (which were covered with semidentine). OK, I'm not sure about the 
> armour of
> certain jawless vertebrates, which were AFAIK also covered by something
> dentine-like. :-)

Are sheep & antelope horns covered in keratin? If so, surely it's a 
thin layer. Have outer-sheath keratin impressions ever been preserved 
with ceratopsian remains? I'm just wondering how much longer/thicker 
the horns actually were beyond the bony core.
Peter M