u/4filen0tfound4

I'm aware the science behind resurrecting these extinct animals is quite dubious, but I think there should be an option to make animals from ancient periods more difficult to unlock than from recent ones. For example, when you start a save, you should be given only Quarternary species, not species like Diplocaulus and Coelophysis, and older formations should have a higher barrier-for-entry, perhaps being locked behind a tech tree node, where each node unlocks digsites from the next-oldest geologic period.