You are in the badlands of North America, 135 million years ago.

The dry, dusty wind of the Early Cretaceous Utah badlands whipped against your face, carrying the scent of iron-rich dust and distant pine. Before you, in a small, arid clearing littered with shattered, sun-bleached clay, a herd of Gastonia was moving, low to the ground. They were small—only about 16 feet long—but packed with over a ton of muscle and bone.

A large individual—perhaps a male, its back bristling with vertical spikes and its shoulders bearing formidable, triangular spikes—paused, bringing its downward-pointed beak near the red earth to crop at a low-lying fern. It was slow, plodding along at a leisurely 5 mph.