You are in the forested plains of North America, 75 million years ago.

The morning sun warmed the ferns in the Montana badlands, where you watched a herd of Orodromeus—small, bipedal ornithopods—grazing in a quiet clearing.

About two dozen of the turkey-sized dinosaurs moved cautiously, their swift bodies, with a sparse coat of feathers, low to the ground as they clipped ferns with their specialized, narrow beaks. The only sound was the soft ripping of plants and the gentle murmuring of the herd.

One individual stood apart, serving as a lookout with head high, pausing frequently to scan for danger. It froze with wide eyes when it spots you observing the herd…