Re: dinosaurs did eat grass

["T. Michael Keesey" <keesey@gmail.com>]

On 11/18/05, Denver Fowler <df9465@yahoo.co.uk> wrote:
>
> The earliest rebbachisaurs are from the European
> Wealden, as are spinosaurs: both taxa typically
> thought of as Gondwanan. The Wealden fauna has strong
> biogeographic links with earlier (Morrison) and
> roughly contemporaneous (Yellow cat-cedar mt) faunas
> of North America. These correlations are as strong as
> any similarity to Gondwanan faunas.

But these rebbachisaurids and spinosaurids are not very much older
than the ones in north Africa, are they? (Barremian vs. Albian?) Is
our sample size big enough to say that these taxa must have originated
in Europe, or might they have originated in Gondwana but left no
(found) trace of their earliest appearance?

Furthermore, skull material is not known for the European
rebbachisaurid _Histriasaurus_, is it? Thus it would be conceivable
that, even if rebbachisaurids first split off from other diplodocoids
in Europe, they may not have developed the unique jaw morphology
before they infiltrated Gondwana.

Come to think of it, rebbachisaurids would have to have split off from
the dicraeosaurid/diplodocid line before the Morrison/Tendaguru,
probably during the Middle Jurassic or at least the Oxfordian, so
we've got a fairly decent ghost lineage here. The earliest known
diplodocimorphs are both Laurasian (Morrison) and Gondwanan
(Tendaguru), so it doesn't seem to me that we have any idea which part
of the globe diplodocimorphs originate from. (Although the presence of
a close relative, _Haplocanthosaurus_, in the Morrison might slightly
favor Laurasian for now, I suppose--but very slightly indeed.)

Who knows?
--
Mike Keesey
The Dinosauricon: http://dino.lm.com
Parry & Carney: http://parryandcarney.com