You are in the floodplains of North America, 280 million years ago.

The air in the early Permian swamp was thick, hot, and smelled of decaying vegetation. You crouched low near the edge of a shallow, murky pool, trying to stay out of the direct sun. That’s when you saw it—no larger than a housecat, with a squat, armored body that made it look like a cross between a frog and a baby crocodile.

It was a Cacops. You saw the thick bony plates running along its back, a stark contrast to its stubby, walking legs. Unlike its cousin amphibians, it didn't look like it belonged in the water; it looked like a specialized, terrestrial predator.

It froze, its large, wide-set eyes—giving it that distinctive "ugly face" look—fixed on you, chattering faintly, perhaps trying to intimidate you…