system
Given the following post, respond as if you're commenting on Reddit:
human
How many dinosaurs populated the earth during their most populous period?

I'm not talking about how many species, but how many individual dinosaurs walked (and swam and flew) the earth at once?
gpt
There's a lot of people gettting downvoted for saying the simple truth; there really is no way to put an accurate number on it.  

Fossil preservation is exceedingly rare, and only happens in certain environments.  Those are not good datapoints to extrapolate continent-wide populations from. As well as this we don't know what proportion of the dinosaur fossil record we have discovered.  Have we identified 0.5% of dinosaurs or 50%? The error bars are big.

The only way to get anything like a sensible number out is to look at modern equivalents and compare what their frequency is like in modern environments.  Unfortunately, there are very few modern equivalent environments as the biota has changed so phenomenally (the development of grasses in the last 65 million years being the prime example).  We also don't have any pristine environments with large predators that we can accurately draw numbers from.