At the base of a pale hill in the badlands of northeastern Wyoming, Susie Maidment hits her hammer against stone. She breaks off a fist-sized chunk, grabs a loose piece between her fingers and places it on her tongue. “Silty,” she announces as the sediment brushes the roof of her mouth.
Maidment’s graduate student, Joe Bonsor, takes note on his clipboard then brings a piece of rock close to his face and squints at it through a hand lens. The layer below this one has slightly larger sand particles, Maidment says — suggesting that the two formed under different conditions. It’s one of many bits of data needed for the job the two paleontologists have come over from the UK to do: piece together, layer by layer, the history of the Late Jurassic, from details in the rocks that formed at that time.
The hills around us on this June day sprawl with dusty prickly pear cactus, juniper and sagebrush. Scorpions and rattlesnakes pose the most immediate threats. But during the Late Jurassic, streams and ponds would have flushed through the landscape, and dinosaurs — the creatures that make this spot so compelling to Maidment and Bonsor — would have sent prey scurrying into shadows.
Along our path, we stop to huddle over a two-inch fossil fragment that Bonsor picked up from the dry rubble — tangible remains of these long-departed animals. Maidment notes that every creature larger than a meter in size that lived on land during the Late Jurassic would have been a dinosaur — and anything with a bone as thick as this one would have come from one. “If it’s big and it’s from the Jurassic,” she says, “it’s a dinosaur bone.”
Dinosaur research has been steadily expanding in recent years, with new fossil discoveries and ever-improving fossil-scanning technology reshaping the way scientists understand these animals that dominated terrestrial ecosystems for more than 130 million years. But fossils on their own can reveal only so much about bigger-picture questions. Do differences in the head crests of hadrosaurs, say, or the skeletons of stegosaurs, represent evolutions through time, or the difference between males and females from the same time? If changes through time, how long did that evolution take, and what caused the shift? Where on the planet were dinosaurs most prevalent and diverse? Who fell prey to whom, and what type of terrain did these creatures carve their lives through? Unearthing additional fossils won’t tell you all these things. The answers, more often, rest in the rocks that surround the bones. And those rocks are, in many cases, not well studied.
