Re: Speculative dino species

[Graydon <graydon@dsl.ca>]

On Sat, Jul 28, 2001 at 09:25:33AM -0500, Andy Farke scripsit:
> 1) What changes would have been initiated by new vegetation? Correct me if
> I'm wrong, mammals evolved unique dental characters in response to the
> advent of grasslands--e.g., horses. Something to consider is how
> ornithischians and sauropods would have been affected. Would the
> hypsilophodont mouth really be equipped to deal with grasses? What about
> ceratopsians and hadrosaurs, with their dental batteries?

Anything with a broad beak and reasonably general digestive processes
ought to be able to deal with grasses; something like an Edmontonosaur
would presumably not find it a difficult change of diet.  The dinosaurs
are in a *much* better position than mammals to cope with this change,
because they've got self-renewing feeding surfaces -- beaks and
continuous tooth replacement -- unlike mammals, which have teeth that
wear out.  I'd expect to see strong evolutionary pressure on grasses to
get tougher, taller, and faster growing.

Hypsilophodonts would presumably have become browsers, the way deer are;
minimal grasses as such, but the low bush-and-sapling pruning niche.

I've seen speculation that ceratopsians were adapted to eat early
angiosperm trees; if that's true, I don't see why they wouldn't have
kept right on doing that.  Would have helped the spread of grasslands,
too, if there was something out there devouring saplings in numbers.
Grasses like bamboo, becoming too tough for the hadrosaurians, might
have become nearly ideal ceratopsian fodder.

Sauropods appear to have had highly efficient digestive systems; it's
also hard to see how they could be picky eaters, on the one hand, given
how much they needed to eat, and how they *couldn't* be, on the other
hand, given how many different species of the things appear to have
shared habitats.

Whatever they were eating, having a better grade of foodstuff become
available might well have lead to a strong sauropod resurgence, as their
survival-to-breeding-age numbers improved as the average growth rate
goes up.  Brings up images of titanosaurs as combine harvesters,
gronching their way across the prairie.

-- 
                           graydon@dsl.ca
               To maintain the end is to uphold the means.