[member="Ultimatum"]
I ask because the reason that dinosaurs and other prehistoric species on Earth grew to any fraction of the size they were was because of the huge amount of oxygen present and the lack of a presence in the biosphere. Compared to today, the Earth was relatively unpopulated - so much so that dragonflies and large insects were the size of small-to-large birds at that point. The larger a total population on a planet, the smaller the size of the species which evolve over time there. The percentage of oxygen is also a factor into size.