1. Optimism
2. If it looks like what is expected, from the right time period current thinking considers likely - it's a good working hypothethis
Personally, I'd be more interested in finding creatures for whom WE are the common ancestor. After all, a couple million years should be more than long enough.
For that matter, any creature for which living organisms that have been around for a couple or more million years are the common ancestor. I'm tired of only looking for common ancestors in the fossil record. Having a living common ancestor would be much more scientifically significant. Why is no one doing any research on that?
Bite your tongue and sign me up for the 2nd revolution already!