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Re: Deciduous horn?



> >There is a very quick way to tell the difference between an animal with
> antlers and horns.  Since antlers are dropped every year, there will be no
> central, bony horncore.  For an example, take a look at the skull of a
> white-tail deer buck; there are cylidrical (sp) projections behind the eye
> (these don't mimic the shape of the antler), the flat tops of these are the
> base for the antlers.  For an animal with a true horn, like a cow, the bony
> part of the horncore will mimic the shape of the horn.  For ceratopians,
> the latter model fits, so they didn't have antlers, they had true horns.
> >Rob Meyerson
> 
> Which, I am afraid, does not answer the question.  Pronghorns have true
> horns, but shed the outer sheath annually.  More to the point, perhaps,
> birds may shed and regrow outer keratin layers such as the ramphotheca of
> the bill as part of the molt process.  I see no reason why horned dinosaurs
> might not have shed the outer horn sheath occasionally even if the bony
> core remained in place, though I have no evidence on the subject.
> 
> Ronald I. Orenstein

It may be true that ceratopsians shed the outer keratin layers of 
their horns - but I am afraid this does not either answer the 
original question why the front horn in ceratopsian fossils shows 
so much variation: The bony part of the horn which is preserved
would not be affected by the changing outer layer.

I cannot imagine that any animal sheds the bony part of a horn. This 
would not be possible without damage to the skull (please correct me 
if such an example is known). So there must be another explanation 
for the variation in ceratopsian horns.

By the way - could anybody tell me what a pronghorn is ?

Martin Jehle, Dipl.-Ing. (FH)
martin.jehle@klinik.uni-regensburg.de
Regensburg, Germany