Remembering dinosaurs were around for, what,.. of the order of 150x longer than humans have, so far....
An occasionally enjoyable gedanken experimenting / daydream / way to get off to sleep is to ask yourself : posit a dino species that developed intelligence and something enough like opposable thumbs to give it human-like ability to manipulate the environment, make tools, etc. Give it a lifetime of 100,000 years (~10x human recorded history) and that it died out in a non-catastrophic way - ecological change causing a drying up of it's preferred food supply, say f'rinstance.
What traces of that would we expect to find in the geological record?
(Yes, this is really just a variant on the "Earth after humans" gedanken... sadly the only way to know will be to run the experiment and then let the aliens / successor intelligent species figure it out in 20m years. I suspect the seabed would be the place to look; uniquitous isotopes and ... layers of carbon... plastics.... zzzzzzzzzzzzzzzz