You are in the forests of South America, 95 million years ago.

The air in the Cretaceous was heavy, thick with the smell of wet pine. The humidity was suffocating, as you trudged across the forested floodplain. A smell hits you first—wet, ancient forest floor mixed with something muskier, sharper. Then, the ground shakes. Not a tremor, but a rhythmic, heavy thud that vibrates through the soles of your boots.

You scrambled behind a colossal, gnarled tree fern to hide. You are just 14-foot-hip-high away from the biggest carnivorous dinosaur you have ever seen, which stepped into the clearing. It was 13 meters, perhaps more, of pure, terrifying, muscle-bound power. The Giganotosaurus.

Its skin was rugged, textured, and covered with small scales that shimmered a muted grey-brown in the sun, fading to a faint, zebra-like striped pattern along its massive spine. The head was unnervingly long and narrow, but it was the 5-foot-long skull that drew your eyes.

It didn't roar, but just grunted—a deep, resonant sound that felt like thunder in your bones—and surveyed its territory with cold, intelligent eyes. This is its valley, and you are in it…