You are in the forests of North America, 98 million years ago.

The air in the early Cretaceous marsh-forest was thick, tasting of wet fern and copper. You were kneeling near the bank of a slow-moving river, documenting a fossilized footprint, when the humid air went perfectly still.

The birds stopped screaming. Even the insects ceased their drone.

Thump.

A low-frequency vibration passed through the mud beneath your knees.

Thump.

It wasn't a roar; it was a heavy, rhythmic breathing, sound radiating from a massive chest. Through the dense canopy, dappled light broke onto the path ahead. Limping, you backed behind a cluster of giant horsetails. Then, it appeared.

It was roughly 30 to 35 feet long, a predator that held its body low and horizontal, moving with terrifying silence for its size.

Siats. The "man-eating monster" of myth was, in the flesh, a tapestry of shades of slate gray and dusky green, perfectly blending into the dim, swampy environment.

You held your breath, realizing this might not be a fully-grown adult, yet it still made the surrounding flora look like grass. Its muscular legs propelled it forward, and its long tail swayed slowly behind it. It stopped, sensing something, turning a massive head towards your hiding spot. You felt your stomach plummet.

Siats wasn't a brutish scavenger. It was a fast, calculating hunter. It didn't roar; it exhaled, a huff of warm air that made the leaves tremble. It was investigating…