Infant dinosaur footprints have been discovered in the foothills west of Denver, Colorado, near the town of Morrison. These tracks were made about 148 million years ago, before the Rocky Mountains rose, when the savanna was full of dinosaurs. According to Matthew Mossbrucker, director of the Morrison Natural History Museum, who discovered the prints, the fossil tracks represent infant sauropods. Sauropods were giant, herbivorous long-necked dinosaurs, sometimes known as "brontosaurs." The...