You are in the forests of North America, 195 million years ago.

The morning mist was still clinging to the red rock canyons of what used to be Arizona. You sat perfectly still behind a scrubby conifer, infrared binoculars trained on the base of a paleodune.

There. A movement.

It was a Segisaurus. Even from fifty feet, the creature looked surprisingly avian—not in feathering, which you couldn’t see, but in its jerky, inquisitive movements. It was barely three feet long, with a sleek, aerodynamic build. It didn’t walk like the heavy-footed dinosaurs you were used to; it moved like a bird, using its long hind legs for rapid, bird-like hopping and running.