Why didn't at least one dinosaur species become human-level smart?

The dinosaurs had hundreds of millions of years where they ruled the
Earth. We mammals were one of the minor species that lived on the
fringes of the dinosaur world. Why didn't the dinosaurs develop a sub-
species with an opposing thumb and that eventually became as smart as
us humans? Is there something about reptiles that prevents them from
developing smart brains? If it hadn't been for an asteroid hitting
the peninsula of Mexico, the dinosaurs would still be ruling our world
and us mammals would still be little more than rats infesting theirs.

Why I ask this here in this newsgroup is because possibly this could
show insight into intelligence by understanding why high intelligence
didn't develop during the long dinosaur era. Then again, has this
point already been figured out? If so, links to such theories would
be appreciated.

Scott
.

Relevant Pages

  • Meteor strike may not have killed dinos/demise began earlier
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  • New Take On Dinosaur Extinction Aftermath
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  • Article: Large mammals once dined on dinosaurs
    ... When the dinosaurs ruled the world, the mammals hid in the shadows, daring ... Named Repenomamus giganticus and Repenomamus robustus, ... dinosaurs filled the niches for large ...
    (sci.bio.evolution)
  • Re: KT boundry event
    ... Evolutionary transformation may turn a dinosaur into a ... Something more 'advanced' than mammals. ... 'Dinosaurs' are extinct. ... BIRDS are NOT dinosaurs! ...
    (talk.origins)
  • Re: Study Re-evaluates Evolution of Mammals
    ... that mammals instantly filled all the niches that had been occupied by ... I remember far back that there was a conjecture stated ... of the dinosaurs, because the new mammals were very good at eating up ... laws of physics, from Newton laws to the spectroscopic laws they used ...
    (talk.origins)