The tangle of the braided Rocky Mountain chain in the western third of the North American continent is relatively new, thrust up to its present height only in Late Cretaceous times. The open river plains of the Jurassic and the steamy forests of the Cretaceous period (the habitats of the most prolific dinosaur communities in the past) are now craggy mountains, clothed in glaciers and snow. A few non-avian dinosaurs adapted to this new environment, moving in from the regions round about and adopting a lifestyle that would support them there. One such is the 2-meter (6 1/2 feet) -long balaclav, one of the specialized modern basal ornithopods. It evolved insulating layers of fat and fur-like protofeathers, an ability to eat the alpine plants including mosses, and a compact shape to preserve its body heat.