You are in the badlands of North America, 110 million years ago.

The air in the Montana basin was thick, smelling of cycads and damp, oxidizing mud. You had been tracking the scent of musk and vegetation for two days. Now, you finally saw them.

Tenontosaurus.

They weren't just one or two; it was a large herd, a herd that seemed to span the entire bank of the meandering river. The sheer size of the adults was overwhelming—at least 25 feet from their blunt, beak-nosed heads to the tip of their long, rigid tails. They moved on four legs, browsing on the lush undergrowth, but the largest one—a dominant female, surely—stood on two legs for a moment, pulling down a high branch of a ginkgo tree with ease.

You counted nearly fifteen, including a few smaller, younger ones huddled close to their mothers. They were acting like Cretaceous cows, noisy and social, a constant low-frequency rumbling communication filling the air.