Re: Horning in

["David Marjanovic" <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. :-)