The westward movement of North America forms the ancestral Rocky Mountains and the ancestral Sierra Nevada. The global climate is generally warm. The poles are free of ice. Dinosaurs and other large reptiles peak as the dominant vertebrate life form on Earth. Dinosaurs extend their range throughout every continent.
Horned dinosaurs are common, as are armored ankylosaurs and spiky nodosaurs .
In the shallow seas, invertebrates live in great diversity. Ammonites are a dominant group. Gastropods , corals, sea urchins flourish. Extinctions also occur among ammonites, corals, and other invertebrates. Age of Mammals.