 In 1961, Zallinger began work on the 60-feet (18.3 meters) by 5.5 feet (1.7 meters) mural on the south wall of the Hall of Mammalian Evolution in Yale's Peabody Museum of Natural History.Its chronology moves from right to left, and it depicts a variety of plants, animals and landscapes of western North American in the span of 65 million years.It shows the domination of mammals after the extinction of dinosaurs 65 million years ago to the Ice age about 10,000 years ago.