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Re: The extinction of small dinosaurs

Extinction isn't a matter of what gets killed or doesn't. It has
everything to do with reproductive success. Complex organisms that are
prone to inbreeding will suffer more from an extinction event than those
that can successfully mate with siblings for several generations.

If a bolide impact (in association with other stresses) reduced
population levels alarmingly, then those animals that can't survive the
genetic bottle neck will eventually die out. So if 95% of everything on
the planet was killed off (plucking an example figure from nowhere),
then it's not a matter of why some things get killed and others don't.
Every species may suffer similar losses. It's a matter of which species
can survive the genetic bottle neck and which can't. 

Modern rodents can inbreed for several generations if need be. Human
populations, on the other hand, result in severe problems trying to do
the same. If human and rodent populations were reduced to small,
isolated populations unable to have contact with each other, rodents may
well survive in the long term whereas humans wouldn't.

Since theropods would have been a rare component of dinosaurian
ecosystems (being predators and all) then you'd expect them to be able
to survive genetic bottle necks better than herbivores. And guess which
dinosaur group just happens to be the only one still around? :)


Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/