So, this doesn't untap - but it creates 4x 2/1 creatures every single turn? That grow if they attack and survive?

gibber

That's a scary-good ability - make this a 6-cost legendary mythic and go to town.

Admittedly; it anti-synergises with your other fossil stuff; but several of your other cards do too, to it ("Abandon fossils") looks like a deck archetype you're consciously aiming for. So not a real downside at all