Ben Standeven wrote:

we don't actually know that
some of those fossil animals weren't more intelligent than we are,
after all. They just didn't leave any signs of civilization, a hundred
million years later.

For extinct species, you can get clues from the shape of the brain case and from its encephalization quotient: the ratio of brain mass to body mass.  As you would expect, humans have the highest ratio of brain mass to body mass of any of the medium and larger sized animals today.  (This method breaks down for the smallest creatures like insects; obviously you need an animal of sufficient size to have any decent functioning brain.)

The dinosaur Troodon had a brain mass to body mass ratio comparable to a modern baboon.  And I believe that's the highest such ratio for any of the dinosaur genera.  Most had a smaller ratio; the sauropods especially so.  The Permian fauna were even worse.

But even the brain case of Troodon shows that it didn't have prefrontal lobes like the modern human brain or the modern dolphin brain.  So was it intelligent?  Probably at the level of a monkey or a cat.  Not like a human or a dolphin.

Finally, notice that "civilization" advanced relatively rapidly once humans developed those prefrontal lobes.  In the space of just 150,000 years (which is tiny compared to the age of the earth), we advanced from spears and stone axes to interplanetary spaceships.  The dinosaurs had 160 million years to play around and never did any such thing--or they would have been all through our Solar System by now.  That tells you they didn't have that level of intelligence.  It's a kind of "Fermi Paradox" applied to extinct species right here on earth.