You are in the forests of North America, 152 million years ago.

The air was thick, humid, and smelled of volcanic ash and rotting vegetation in the Late Jurassic inland basin of Utah. You crouched behind the thick fronds of a cycad, checking on a juvenile Diplodocus that had become separated from its herd near the muddy floodplain.

Then, the world went quiet. The dragonfly buzzing near your ear vanished.

A flash of beige and green—a patterned, scaly hide—appeared from the periphery. Roughly 28 feet long, it moves with terrifying speed on two massive hind legs. Its short, bony nasal crests caught the sunlight as it turned its head toward the young sauropod. You instantly recognize it as an Allosaurus.

It did not roar. It attacked in silence.

The Allosaurus did not make a head-on charge. Instead, it used a bursting, angling approach, taking advantage of its long legs. As it got close, it didn’t slam its head down like a hatchet, as some theories suggest; instead, it opened its jaws impossibly wide, revealing rows of sharp, backward-curved serrated teeth.