“I wouldn’t ask if I didn’t.”

With a mental shrug, Leyster booted up first his computer and then the trackway program, routing the image to a high-density monitor hung on the wall. The image was as detailed as modern technology could make it. He had provided multiple photographs of each track and Ralph Chapman, down the hall, had come up with a 3-D merge-and-justify routine for them. The program began at the far end of the trackway.

“What do you see?” he asked.

“Footprints,” Griffin said, “in mud.”

“So they were, once. Which is what makes them so exciting. When you dig up fossil bones, that’s the record of a dead animal. But here, this—this was made by living animals. They were alive and breathing the day they made these, and for one of them it was a very significant day indeed. Let me walk you through it.”

He held one hand on the trackball, so he could scroll through the program as he talked. “One hundred forty million years ago, an Apatosaurus—what used to known as Brontosaurus, before the taxon was reattributed—is out for a stroll along the shores of a shallow lake. See how steady the apatosaur’s prints are, how placidly it ambles along. It is not yet aware that it’s being hunted.”

Griffin gravely folded his hands as Leyster scrolled down the trackway. They were enormous hands, even for a man of his bulk, and strangely expressive.

“Now look at these smaller sets of prints here and here, coming out of the forest and following along to either side of the apatosaur’s prints. These belong to a hunting pair of Allosaurus fragilis. Killer dinosaurs twelve meters long, with enormous sharp claws on their hands and feet, and teeth as large as daggers but with a serrated edge. They move more swiftly than their prey, but they’re not running yet—they’re stalking. Notice how they’ve already positioned themselves so they can come up on it from either side.