You are in the forests of China, Asia, 160 million years ago.

The air in the basin was thick and humid, filled with the scent of cycads and damp earth. You were carefully mapping the edge of a slow-moving river, documenting the local fauna when the chatter of small pterosaurs suddenly stopped.

Just then, you spot a huge shape moving between the dense, tree-sized ferns. It was nearly 30 feet long, a blur of dusky green and slate grey scales. A Yangchuanosaurus.

It moved with surprising speed on two powerful, muscular legs, its long tail holding it in perfect balance. Its head was massive, adorned with faint bony ridges over the eyes—an Allosaurus of the East, but somehow more terrifying in the claustrophobic forest.

The carnivore hadn't seen you yet. It was watching a young Mamenchisaurus near the bank. Then, the Yangchuanosaurus lowered its head. The unique, square-jawed profile seemed designed for one purpose. It launched forward, acting like a living hatchet, throwing its weight behind a down-turned bite meant to inflict a deep, bleeding wound.

The young sauropod roared, thrashing wildly. The Yangchuanosaurus didn't hold on, but rather let go instantly, ready to strike again, using its serrated teeth to rip and slash. It was a terrifyingly efficient predator, a 3-ton apex carnivore in its prime.

As the Mamenchisaurus herd panicked and surged, the Yangchuanosaurus turned its gaze toward the path you are hiding on, its muscular, neck giving it a flexible, terrifying range of motion…