Dinosaur diversity

[Jonathon Woolf <jwoolf@erinet.com>]

Random musings . . . 

Among the books in my dino-library is THE NEW DINOSAURS by Dougal Dixon,
a sharp, whimsical, and wildly fun ride into a world of "future
dinosaurs," what evolution might have produced from Cretaceous dinosaurs
and other animals had the K-T extinction never happened.  Some of
Dixon's animals are just too fantastic to believe, but others I find
very believable, like "whulks" (whale-size krill-eating pliosaurs),
"sprintosaurs" (plains-dwelling hadrosaurs with flaglike tails), and
"arbrosaurs" (very small, exclusively arboreal coelurosaurs).  Which
leads to a question: IMO Dixon is right that these animals _could have_
evolved from dinosaurs in sixty-five million years -- so why didn't
they?  Dinosaurs dominated land ecosystems for a hundred and fifty
million years, but don't seem to have changed a whole lot for much of
that period.  I see bursts of diversification, like those that produced
the ceratopsids and hadrosaurs, but overall there seems to be a strange
"sameness" about dinosaurian faunas for large periods of time.  

Comments, thoughts, ideas, anyone?

-- JSW