Eighty-four-year-old Sheldon Johnson never imagined that once he began digging, it would be so difficult to stop. In February 2000, he climbed into his trackhoe and drove up to a 40-foot hill on his small farm in southern Utah. The rusty sandstone mound did not match the level of the adjacent new city road, and the retired optometrist simply wanted to level it. Johnson busily went to work hauling out 15-foot-long rectangular slabs of the red rock. Then the trackhoe flipped one of the slabs over, and Johnson saw them: pristinely preserved dinosaur footprints. “It was unmistakable. I could see knuckles, claws, scales, and three big toes. No one hardly believed me at first,” he says.
Johnson immediately began turning over more layers of sandstone, breathlessly checking their underbellies for tracks. To his delight, nearly every one had some of the monstrous prints. He called around to state offices and universities, and within a matter of weeks hundreds of curious spectators—children, government officials, paleontologists—began flocking to the farm. Over the next few years, thousands of tracks were unearthed at the location now known as the St. George Dinosaur Discovery Site at Johnson Farm. Johnson had stumbled onto one of the world’s most important dinosaur trackways.
Once dismissed by most paleontologists as mere curiosities, trackways are increasingly being recognized as vital pieces of evidence that record otherwise unknowable details of daily life millions of years ago. Fossil bones are wonderful for understanding anatomy, but they are inherently static. Footprints and other impressions, on the other hand, are snapshots of a creature in action. “When you hold a bone of an extinct animal, you’re holding a remain,” says University of Manchester paleontologist Phillip Manning. “Trackways are from when the animal is still breathing.”
Martin Lockley, a University of Colorado paleontologist, has spent nearly three decades analyzing ancient prints. “Tracks are very dynamic,” he says. “They show things like speed, individual behavior, social behavior, and animals starting to run. They’re a quick way to get a lot of information.” A track site representing several types of dinosaurs can reveal which major groups cohabited, indicate the proportion of juveniles to adults, and offer a general census of the populations in the area.
