Tree biloba". This is considered to be a living fossil because it is virtually unchanged from the fossilised specimens found in Triassic deposits. During the Mesozoic (245 to 66 million years ago) the conifers flourished and became adapted to live in all the major terrestrial habitats. Subsequently, the tree forms of flowering plants evolved during the Cretaceous period. These began to displace the conifers during the Tertiary era (66 to 2 million years ago) when forests covered the globe. When the climate cooled 1.5 million years ago and the first of four ice ages occurred, the forests retreated as the ice
Rocky Mountain National Park creating the ancestral Rocky Mountains. Fountain Formation was deposited during the Pennsylvanian period of the Paleozoic era, 290–296 million years ago. Over the next 150 million years, the mountains uplifted, continued to erode, and covered themselves in their own sediment. Wind, gravity, rainwater, snow, and glacial ice eroded the granite mountains over geologic time scales. The Ancestral Rockies were eventually buried under subsequent strata. The Pierre Shale formation was deposited during the Paleogene and Cretaceous periods about 70 million years ago. The region was covered by a deep seathe Cretaceous Western Interior Seawaywhich deposited massive amounts of shale on the