>>57447479First fossil was Kabuto, Kabutops is one of my favorite mons. I've used every fossilmon at least once in every gen playthrough except for Arctovish I think.
Also shiny hunted a Amaura in Gen 8, hopefully I can transfer it to Z/A.
I feel like we haven't gotten a proper pteranodon or stegosaurus which are pretty staple dinosaurs, so I wouldn't mind seeing that.
If we're going non-dinos, maybe Indricotherium (largest land mammal that existed), or Sabertooth tigers.
I also wouldn't mind if they did something like Past-Paradox mons but as a regional variant, like if there was a prehistoric Venipede variant that went extinct in the new region, and the only way to get it was to revive it from its fossil.