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large body size vs little dinos



I really liked your explanation in terms of energy needed.  In catyclismic
times, this energy would be harder to come by, so the individual needed to
spend more to get less....
     But what about the small-body mass dinosaurs?  Like Troodon,  or
Velociraptor Mongolensis?  We know that crocodilians survived the extinction,
and crocs can get much bigger than any recorded find of either of these two.
  I may not be familiar with other types by name, but after 165 million years
of a dinosaur age there statistically had to be dinosaurs of small body mass,
like Hipsephaladon, but from the Late Cretaceous.   Where were the dinosaur
non-specialists?   Its the same law as the one about the number of books you
own will always be greater than the places you can put them, dinosaurs were
around so long that they had to evolve into every available niche.
   Its that genetic diversity thing again.  Unless the non-specialists were
out-competed by the mammals and birds in an earlier age, and replaced by
them. I'll give you that the small non-specialist dinosaurs could have
already been extinct at this time.  
   what type of birds survived the extinction?  Well, I know about ducks(a
specialist, but an opportunistis specialist even today), aand pidgeons.  If
the really large birds evolved shortly after the dinosaur extinction to fill
the empty niche, what did they evolve from? Were there herons or storks?
 Their body mass isn"t much smaller than a Velociraptor.
     I don't think it could have been exclusivly body size, but I don't want
to eliminate non-specialization.  But not have a functional pineal gland
could be considered as a special evolution, where sacrificing the use of one
gained something else, such as a better protected skull, or pointy bits on
the head, or something.