From the press release:
Newly Discovered Fossil Footprints from Grand Canyon National Park Force Paleontologists to Rethink Early Inhabitants of Ancient Deserts
Map of Arizona (southwestern USA), indicating the main localities mentioned in the text. The Grand Canyon National Park area is shaded dark brown (left). Stratigraphic section of the Pennsylvanian and Permian rocks exposed in the Grand Canyon area (right). Modified from Blakey and Knepp 1989.
Note: Representative image at left is often cropped for display purposes. Downloaded high-resolution images are not cropped.