Re: grass

[Jordan Mallon <jordan.mallon@gmail.com>]

On 11/7/06, Dann Pigdon <dannj@alphalink.com.au> wrote:

> The basic ceratopian jaw mechanics didn't seem to change much from
> Protoceratops onwards (except for becoming bigger and more powerful).

My feeling is that it's probably too early to say much in that regard.
Frank Varriale, one of Weishampel's students, is busy working out
ceratopsian jaw mechanics as we speak.  There are numerous changes to
the mandible over the evolution of the Ceratopsia having to do with
the relative lengths of the jaws and tooth rows, shearing
orientiation, coronoid height, etc.

> If they were to become specialist grazers later on, I'd expect
radical changes in the
> shape of the beak (compare the muzzle shapes of mainly-browsing black rhinos to
> mainly-grazing white rhinos).

Meh.  The wide beak = grazer; narrow beak = browser dichotomy isn't a
hard and fast rule, as I'm sure you know.  My feeling is that the
narrow beaks of ceratopsids were more a result of their phylogenetic
history than of their ecologies (like some grazing kangaroos and
horses).  Maybe the evolution of the rostral bone locked ceratopsids
into the 'browser' niche.

>  I think there are too many 'maybes' concerning Mesozoic
> grass (if it existed at all) to be able to make any assumptions of its
> ecological role.

Definitely agree there.

--
Jordan Mallon

M.Sc. student, University of Calgary
http://homepages.ucalgary.ca/~jmallon/