You are in the mountain plains of North America, 70 million years ago.

The ground beneath your feet was no longer dirt; it was a rhythmic, thunderous vibration that shook you to your bones. You braced yourself against a weathered coniferous tree, watching the horizon turn into a solid, moving wall of thick, blunt-nosed beasts.

Pachyrhinosaurus.

They were migrating, thousands of them, a slow-moving river of keratin, muscle, and dust-colored hide moving north for the summer. You were merely a fleeting witness to their 400-mile odyssey. They didn’t have horns like a Triceratops; instead, they had massive, flattened bosses—thick, bony lumps of armor on their noses and over their eyes. They looked like living, breathing bulldozers.

The air was filled with a cacophony of sound: low, rumbles of communication, the sharp snuffing of heavy breaths, and the crunching of cycads being torn from the ground. And they just kept walking.