You are in the coastal swamps of North America, 76 million years ago.

The heat in the Late Cretaceous of southern Utah was absolute—a suffocating blanket of moisture, smelled of petrified mud and, suddenly, rotting meat. You froze behind the roots of a towering cypress tree, peering through the humid gloom of the coastal swamp.

A crunching sound, like a tree limb snapping, echoed from behind the fern banks. It appeared slowly, a 25-foot titan of muscle and rage. A Teratophoneus.

Unlike the smooth face of a T. rex, this one had a terrifyingly short, blunt snout, packed with daggers. It was a "monstrous murderer" in every sense, and its jaws were painted with the crimson of a recent kill. Its legs were unusually long, built for chasing down prey in this swampy environment, and its yellow eyes scanned the clearing with terrifying intensity, seemingly resting on your hiding spot...