We need a standalone fossil like gen 1 too, Megalodon could be great but you could have a Spinosaurus because we got enough Water/Rock fossils for now another one we could see is one of the first Mammals to have been on earth, for now we mostly got plant, dinosaurs, crustaceas(ancestors of bugs), birds,amphibians and mollusks. Mammals and fishes are not here yet, Relicanth count mostly as pseudo fossil since it's an alive fossil same could be said about Mammoswine, also Anorith line don't really count as a real bug since it looks more like a crustacea. Also I could see some centipede, land arthropod and sandworms.