BEARS EARS NATIONAL MONUMENT IN UTAH—On a rise with a sweeping view of the Indian Creek valley in southern Utah, skirts of red earth unfurling for kilometers in all directions, Adam Huttenlocker crouches to examine a knee-high nub of Cedar Mesa sandstone. Embedded in the rock is an ivory oval with a smoky center. The paleontologist, from the University of Southern California in Los Angeles, leans in for a closer look. Other researchers gather round, and soon they identify the mysterious eyelike fragment: It is a cross section of limb bone, probably from a synapsid—the group of reptiles that gave rise to mammals—that lived here more than 300 million years ago.
Thousands of such rare fossils pepper Bears Ears, a sweep of buttes and badlands whose candy-striped sedimentary rocks catalog hundreds of millions of years of Earth's history. The region's rich paleontological and archaeological record—and the lobbying of southwestern tribes whose ancestors lived here—persuaded former President Barack Obama to designate the area a national monument just over 2 years ago, in the waning days of his administration.