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On Fri, 1 Dec 1995 Dinogeorge@aol.com wrote:

> Also small non-insect invertebrates. By the way, BCF hypothesizes that
> primitive avian teeth were unserrated (don't know about the constrictions in
> Archy teeth, though), so that each large-theropod lineage developed its own
> kind of serrated teeth independently. So now I (at least) understand why
> theropod teeth have differently shaped serrations, and why theopod tooth
> taxonomy is pretty good to the family level. This makes "serrated teeth" a
> lousy synapomorphy.

        This could also be interpreted as the idea that large predators 
tended to evolve from the small theropods, rather than from other large 
predators. Big animals, I am guessing, do pretty well in relatively 
stable situations, while small animals clean up when things go haywire. 
Big animals go extinct more easily, possibly (look at the last ice age), 
just because A) there are fewer of them B) because there are fewer of 
them, the number of different genes they might have would be different 
C)they take longer to reproduce, so evolution cannot procede as quickly 
amng elephants as, say, mice which can run through a couple generations 
per year. Of course, big animals have a lot of advantages too. They can 
be very efficient, migrate huge distances, and eat low quality food. 
The general impression I often seem to get from land animals is 
that small animals evolve into big animals and more small animals, then 
the big animals go extinct (repeat as necessary). Anyways, just some 
vague thoughts on the subject.