of period—Rocky dinosaurs; first Mountains formed. flowering plants and grasses. Mesozoic Jurassic 38 M.Y. Continent emergent; Rise of birds and shallow seas on flying reptiles, western North first modern America. trees. Triassic 35 M.Y. Continent emergent; Rise of seas marginal. dinosaurs, cycads, and ammonites. Paleozoic Permian 35 M.Y. World-wide Extinction of continental uplift most Paleozoic and mountain fauna and flora. building. First modern Widespread insects. glaciation. Pennsylvanian 48 M.Y. Continent Great alternately rising coal-forming and sinking. forests, of ferns and seed-ferns. Mississippian 35 M.Y. Low lands and Culmination of widespread crinoids, submergence. numerous sharks. Devonian 40 M.Y. Widespread First known land submergence, local animals, first vulcanism. forests. Silurian 28 M.Y. Widespread First lung fishes submergence, local and scorpions, deserts. abundant corals. Ordovician 65 M.Y. 60% of North Climax of America below sea. invertebrate dominance, first vertebrate. Cambrian 105 M.Y. Widespread First abundant submergence. invertebrate fauna, trilobites dominant. Proterozoic 700 ± M.Y. Long periods of Bacteria and granite intrusion, seaweeds present.