Re: The Cretaceous Middle-East

[Stanley Friesen <sarima@friesen.net>]

At 11:22 AM 9/19/00 -0400, Brent Jones wrote:
> Hello, I'm a first time contributor. I've been reading along, and thought 
> this was a topic I might have some thoughts on...
>
> I don't know how bizarre the new shapes would be. After all, in a small 
> community like what is being proposed here, wouldn't conservatism apply?

Not particularly.  In fact small populations tend to evolve *faster* than 
larger ones, due to greater genetic drift and quicker fixation of alleles 
by selection.  Widespread, common species are often the most conservative.

> adapt to fit in with their new, smaller environment. Pygmy species would 
> abound, and they would evolve ceratin characteristics to better utilize 
> their environment, but would their evolution lead towards the truly 
> bizarre? (I know, what is bizarre to a human may not be so bizarre for a 
> dinosaur that has survived in a small refuge in Yemen...)

I agree, bizarre is not necessarily all that likely, but the forms would be 
greatly different than any known fossil.  However, display structures, like 
crests, sails, ridges, and so on, tend to evolve very fast indeed, and 
often become quite extreme.  Countering this would be low diversity - 
display structures tend to be most exuberant where there are several 
closely related species interacting.

> Besides, to make these dinosaurs really recognizable to the general 
> public, they would have to evolve along fairly "normal" lines: pygmy 
> tyrannosaurs, with tiny forelimbs ending in two tiny claws, huge head in 
> comparison with the rest of the body, etc;

But not so huge, relatively speaking, as in a full sized 
tyrannosaur.  Scaling in animals is rarely linear, and the head would 
shrink faster than the rest of the body.

> pygmy ceratopians, with (perhaps) more frills, shorter horns (less likely 
> to entangle in the smaller, cramped environment);

This depends: is there one species of pygmy ceratopsian or several?  If 
only one, even the frill may well be reduced as redundant.

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May the peace of God be with you.         sarima@ix.netcom.com