I agree with Shadow D. Darkman, the Chronoverse doesn't exactly hold true to factual science, so this thread is pointless.
Oh, and your original statement of "nothing surviving a 65 M year ice age" is incorrect. Even if it did cover the entire planet, aquatic plants and animals would survive just fine, even in shallow waters, and so would innumerable species of extremophile bacteria. Also, chemoautotrophic bacteria and the ecosystems based upon them around thermal vents on the ocean floor would likely be unaffected by any extreme geological activity on the planet.
But once again, it's a video game, not reality.